Changeset 1633


Ignore:
Timestamp:
28/03/12 17:34:31 (8 years ago)
Author:
julian.reschke@…
Message:

sort header fields

Location:
draft-ietf-httpbis/experiment
Files:
4 edited

Legend:

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  • draft-ietf-httpbis/experiment/p2-semantics.html

    r1631 r1633  
    723723         </li>
    724724         <li>9.&nbsp;&nbsp;&nbsp;<a href="#header.field.definitions">Header Field Definitions</a><ul>
    725                <li>9.1&nbsp;&nbsp;&nbsp;<a href="#header.allow">Allow</a></li>
    726                <li>9.2&nbsp;&nbsp;&nbsp;<a href="#header.date">Date</a></li>
    727                <li>9.3&nbsp;&nbsp;&nbsp;<a href="#header.expect">Expect</a></li>
    728                <li>9.4&nbsp;&nbsp;&nbsp;<a href="#header.from">From</a></li>
    729                <li>9.5&nbsp;&nbsp;&nbsp;<a href="#header.location">Location</a></li>
    730                <li>9.6&nbsp;&nbsp;&nbsp;<a href="#header.max-forwards">Max-Forwards</a></li>
    731                <li>9.7&nbsp;&nbsp;&nbsp;<a href="#header.referer">Referer</a></li>
    732                <li>9.8&nbsp;&nbsp;&nbsp;<a href="#header.retry-after">Retry-After</a></li>
    733                <li>9.9&nbsp;&nbsp;&nbsp;<a href="#header.server">Server</a></li>
    734                <li>9.10&nbsp;&nbsp;&nbsp;<a href="#header.user-agent">User-Agent</a></li>
    735                <li>9.11&nbsp;&nbsp;&nbsp;<a href="#header.accept">Accept</a></li>
    736                <li>9.12&nbsp;&nbsp;&nbsp;<a href="#header.accept-charset">Accept-Charset</a></li>
    737                <li>9.13&nbsp;&nbsp;&nbsp;<a href="#header.accept-encoding">Accept-Encoding</a></li>
    738                <li>9.14&nbsp;&nbsp;&nbsp;<a href="#header.accept-language">Accept-Language</a></li>
    739                <li>9.15&nbsp;&nbsp;&nbsp;<a href="#header.content-encoding">Content-Encoding</a></li>
    740                <li>9.16&nbsp;&nbsp;&nbsp;<a href="#header.content-language">Content-Language</a></li>
    741                <li>9.17&nbsp;&nbsp;&nbsp;<a href="#header.content-location">Content-Location</a></li>
    742                <li>9.18&nbsp;&nbsp;&nbsp;<a href="#header.content-type">Content-Type</a></li>
     725               <li>9.1&nbsp;&nbsp;&nbsp;<a href="#header.accept">Accept</a></li>
     726               <li>9.2&nbsp;&nbsp;&nbsp;<a href="#header.accept-charset">Accept-Charset</a></li>
     727               <li>9.3&nbsp;&nbsp;&nbsp;<a href="#header.accept-encoding">Accept-Encoding</a></li>
     728               <li>9.4&nbsp;&nbsp;&nbsp;<a href="#header.accept-language">Accept-Language</a></li>
     729               <li>9.5&nbsp;&nbsp;&nbsp;<a href="#header.allow">Allow</a></li>
     730               <li>9.6&nbsp;&nbsp;&nbsp;<a href="#header.content-encoding">Content-Encoding</a></li>
     731               <li>9.7&nbsp;&nbsp;&nbsp;<a href="#header.content-language">Content-Language</a></li>
     732               <li>9.8&nbsp;&nbsp;&nbsp;<a href="#header.content-location">Content-Location</a></li>
     733               <li>9.9&nbsp;&nbsp;&nbsp;<a href="#header.content-type">Content-Type</a></li>
     734               <li>9.10&nbsp;&nbsp;&nbsp;<a href="#header.date">Date</a></li>
     735               <li>9.11&nbsp;&nbsp;&nbsp;<a href="#header.expect">Expect</a></li>
     736               <li>9.12&nbsp;&nbsp;&nbsp;<a href="#header.from">From</a></li>
     737               <li>9.13&nbsp;&nbsp;&nbsp;<a href="#header.location">Location</a></li>
     738               <li>9.14&nbsp;&nbsp;&nbsp;<a href="#header.max-forwards">Max-Forwards</a></li>
     739               <li>9.15&nbsp;&nbsp;&nbsp;<a href="#header.referer">Referer</a></li>
     740               <li>9.16&nbsp;&nbsp;&nbsp;<a href="#header.retry-after">Retry-After</a></li>
     741               <li>9.17&nbsp;&nbsp;&nbsp;<a href="#header.server">Server</a></li>
     742               <li>9.18&nbsp;&nbsp;&nbsp;<a href="#header.user-agent">User-Agent</a></li>
    743743            </ul>
    744744         </li>
    … …  
    903903      </p>
    904904      <div id="rfc.figure.u.3"></div><pre class="inline"><span id="rfc.iref.g.1"></span>  <a href="#methods" class="smpl">method</a>         = <a href="#core.rules" class="smpl">token</a>
    905 </pre><p id="rfc.section.2.p.3">The list of methods allowed by a resource can be specified in an Allow header field (<a href="#header.allow" id="rfc.xref.header.allow.1" title="Allow">Section&nbsp;9.1</a>). The status code of the response always notifies the client whether a method is currently allowed on a resource, since the
     905</pre><p id="rfc.section.2.p.3">The list of methods allowed by a resource can be specified in an Allow header field (<a href="#header.allow" id="rfc.xref.header.allow.1" title="Allow">Section&nbsp;9.5</a>). The status code of the response always notifies the client whether a method is currently allowed on a resource, since the
    906906         set of allowed methods can change dynamically. An origin server <em class="bcp14">SHOULD</em> respond with the status code 405 (Method Not Allowed) if the method is known by the origin server but not allowed for the
    907907         resource, and 501 (Not Implemented) if the method is unrecognized or not implemented by the origin server. The methods GET
    … …  
    983983         but might be defined by future extensions to HTTP. Content negotiation <em class="bcp14">MAY</em> be used to select the appropriate response format. If no response body is included, the response <em class="bcp14">MUST</em> include a Content-Length field with a field-value of "0".
    984984      </p>
    985       <p id="rfc.section.2.3.1.p.7">The Max-Forwards header field <em class="bcp14">MAY</em> be used to target a specific proxy in the request chain (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.1" title="Max-Forwards">Section&nbsp;9.6</a>). If no Max-Forwards field is present in the request, then the forwarded request <em class="bcp14">MUST NOT</em> include a Max-Forwards field.
     985      <p id="rfc.section.2.3.1.p.7">The Max-Forwards header field <em class="bcp14">MAY</em> be used to target a specific proxy in the request chain (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.1" title="Max-Forwards">Section&nbsp;9.14</a>). If no Max-Forwards field is present in the request, then the forwarded request <em class="bcp14">MUST NOT</em> include a Max-Forwards field.
    986986      </p>
    987987      <h3 id="rfc.section.2.3.2"><a href="#rfc.section.2.3.2">2.3.2</a>&nbsp;<a id="GET" href="#GET">GET</a></h3>
    … …  
    10411041      </p>
    10421042      <p id="rfc.section.2.3.4.p.4">If a resource has been created on the origin server, the response <em class="bcp14">SHOULD</em> be 201 (Created) and contain a representation which describes the status of the request and refers to the new resource, and
    1043          a Location header field (see <a href="#header.location" id="rfc.xref.header.location.1" title="Location">Section&nbsp;9.5</a>).
    1044       </p>
    1045       <p id="rfc.section.2.3.4.p.5">Responses to POST requests are only cacheable when they include explicit freshness information (see <a href="p6-cache.html#calculating.freshness.lifetime" title="Calculating Freshness Lifetime">Section 2.3.1</a> of <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). A cached POST response with a Content-Location header field (see <a href="#header.content-location" id="rfc.xref.header.content-location.1" title="Content-Location">Section&nbsp;9.17</a>) whose value is the effective Request URI <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests.
     1043         a Location header field (see <a href="#header.location" id="rfc.xref.header.location.1" title="Location">Section&nbsp;9.13</a>).
     1044      </p>
     1045      <p id="rfc.section.2.3.4.p.5">Responses to POST requests are only cacheable when they include explicit freshness information (see <a href="p6-cache.html#calculating.freshness.lifetime" title="Calculating Freshness Lifetime">Section 2.3.1</a> of <a href="#Part6" id="rfc.xref.Part6.4"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>). A cached POST response with a Content-Location header field (see <a href="#header.content-location" id="rfc.xref.header.content-location.1" title="Content-Location">Section&nbsp;9.8</a>) whose value is the effective Request URI <em class="bcp14">MAY</em> be used to satisfy subsequent GET and HEAD requests.
    10461046      </p>
    10471047      <p id="rfc.section.2.3.4.p.6">Note that POST caching is not widely implemented. However, the 303 (See Other) response can be used to direct the user agent
    … …  
    11311131      <div id="rfc.iref.m.7"></div>
    11321132      <p id="rfc.section.2.3.7.p.1">The TRACE method requests a remote, application-layer loop-back of the request message. The final recipient of the request <em class="bcp14">SHOULD</em> reflect the message received back to the client as the message body of a 200 (OK) response. The final recipient is either
    1133          the origin server or the first proxy to receive a Max-Forwards value of zero (0) in the request (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.2" title="Max-Forwards">Section&nbsp;9.6</a>). A TRACE request <em class="bcp14">MUST NOT</em> include a message body.
     1133         the origin server or the first proxy to receive a Max-Forwards value of zero (0) in the request (see <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.2" title="Max-Forwards">Section&nbsp;9.14</a>). A TRACE request <em class="bcp14">MUST NOT</em> include a message body.
    11341134      </p>
    11351135      <p id="rfc.section.2.3.7.p.2">TRACE allows the client to see what is being received at the other end of the request chain and use that data for testing
    … …  
    12061206         double quotes will likely cause unnecessary confusion.
    12071207      </p>
    1208       <p id="rfc.section.3.1.p.8">Many header fields use a format including (case-insensitively) named parameters (for instance, Content-Type, defined in <a href="#header.content-type" id="rfc.xref.header.content-type.1" title="Content-Type">Section&nbsp;9.18</a>). Allowing both unquoted (token) and quoted (quoted-string) syntax for the parameter value enables recipients to use existing
     1208      <p id="rfc.section.3.1.p.8">Many header fields use a format including (case-insensitively) named parameters (for instance, Content-Type, defined in <a href="#header.content-type" id="rfc.xref.header.content-type.1" title="Content-Type">Section&nbsp;9.9</a>). Allowing both unquoted (token) and quoted (quoted-string) syntax for the parameter value enables recipients to use existing
    12091209         parser components. When allowing both forms, the meaning of a parameter value ought to be independent of the syntax used for
    12101210         it (for an example, see the notes on parameter handling for media types in <a href="#media.types" title="Media Types">Section&nbsp;5.5</a>).
    … …  
    12631263               <tr>
    12641264                  <td class="left">Accept</td>
    1265                   <td class="left"><a href="#header.accept" id="rfc.xref.header.accept.1" title="Accept">Section&nbsp;9.11</a></td>
     1265                  <td class="left"><a href="#header.accept" id="rfc.xref.header.accept.1" title="Accept">Section&nbsp;9.1</a></td>
    12661266               </tr>
    12671267               <tr>
    12681268                  <td class="left">Accept-Charset</td>
    1269                   <td class="left"><a href="#header.accept-charset" id="rfc.xref.header.accept-charset.1" title="Accept-Charset">Section&nbsp;9.12</a></td>
     1269                  <td class="left"><a href="#header.accept-charset" id="rfc.xref.header.accept-charset.1" title="Accept-Charset">Section&nbsp;9.2</a></td>
    12701270               </tr>
    12711271               <tr>
    12721272                  <td class="left">Accept-Encoding</td>
    1273                   <td class="left"><a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.1" title="Accept-Encoding">Section&nbsp;9.13</a></td>
     1273                  <td class="left"><a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.1" title="Accept-Encoding">Section&nbsp;9.3</a></td>
    12741274               </tr>
    12751275               <tr>
    12761276                  <td class="left">Accept-Language</td>
    1277                   <td class="left"><a href="#header.accept-language" id="rfc.xref.header.accept-language.1" title="Accept-Language">Section&nbsp;9.14</a></td>
     1277                  <td class="left"><a href="#header.accept-language" id="rfc.xref.header.accept-language.1" title="Accept-Language">Section&nbsp;9.4</a></td>
    12781278               </tr>
    12791279               <tr>
    … …  
    12831283               <tr>
    12841284                  <td class="left">Expect</td>
    1285                   <td class="left"><a href="#header.expect" id="rfc.xref.header.expect.1" title="Expect">Section&nbsp;9.3</a></td>
     1285                  <td class="left"><a href="#header.expect" id="rfc.xref.header.expect.1" title="Expect">Section&nbsp;9.11</a></td>
    12861286               </tr>
    12871287               <tr>
    12881288                  <td class="left">From</td>
    1289                   <td class="left"><a href="#header.from" id="rfc.xref.header.from.1" title="From">Section&nbsp;9.4</a></td>
     1289                  <td class="left"><a href="#header.from" id="rfc.xref.header.from.1" title="From">Section&nbsp;9.12</a></td>
    12901290               </tr>
    12911291               <tr>
    … …  
    13151315               <tr>
    13161316                  <td class="left">Max-Forwards</td>
    1317                   <td class="left"><a href="#header.max-forwards" id="rfc.xref.header.max-forwards.3" title="Max-Forwards">Section&nbsp;9.6</a></td>
     1317                  <td class="left"><a href="#header.max-forwards" id="rfc.xref.header.max-forwards.3" title="Max-Forwards">Section&nbsp;9.14</a></td>
    13181318               </tr>
    13191319               <tr>
    … …  
    13271327               <tr>
    13281328                  <td class="left">Referer</td>
    1329                   <td class="left"><a href="#header.referer" id="rfc.xref.header.referer.1" title="Referer">Section&nbsp;9.7</a></td>
     1329                  <td class="left"><a href="#header.referer" id="rfc.xref.header.referer.1" title="Referer">Section&nbsp;9.15</a></td>
    13301330               </tr>
    13311331               <tr>
    … …  
    13351335               <tr>
    13361336                  <td class="left">User-Agent</td>
    1337                   <td class="left"><a href="#header.user-agent" id="rfc.xref.header.user-agent.1" title="User-Agent">Section&nbsp;9.10</a></td>
     1337                  <td class="left"><a href="#header.user-agent" id="rfc.xref.header.user-agent.1" title="User-Agent">Section&nbsp;9.18</a></td>
    13381338               </tr>
    13391339            </tbody>
    … …  
    13631363               <tr>
    13641364                  <td class="left">Allow</td>
    1365                   <td class="left"><a href="#header.allow" id="rfc.xref.header.allow.2" title="Allow">Section&nbsp;9.1</a></td>
     1365                  <td class="left"><a href="#header.allow" id="rfc.xref.header.allow.2" title="Allow">Section&nbsp;9.5</a></td>
    13661366               </tr>
    13671367               <tr>
    13681368                  <td class="left">Date</td>
    1369                   <td class="left"><a href="#header.date" id="rfc.xref.header.date.1" title="Date">Section&nbsp;9.2</a></td>
     1369                  <td class="left"><a href="#header.date" id="rfc.xref.header.date.1" title="Date">Section&nbsp;9.10</a></td>
    13701370               </tr>
    13711371               <tr>
    … …  
    13751375               <tr>
    13761376                  <td class="left">Location</td>
    1377                   <td class="left"><a href="#header.location" id="rfc.xref.header.location.2" title="Location">Section&nbsp;9.5</a></td>
     1377                  <td class="left"><a href="#header.location" id="rfc.xref.header.location.2" title="Location">Section&nbsp;9.13</a></td>
    13781378               </tr>
    13791379               <tr>
    … …  
    13831383               <tr>
    13841384                  <td class="left">Retry-After</td>
    1385                   <td class="left"><a href="#header.retry-after" id="rfc.xref.header.retry-after.1" title="Retry-After">Section&nbsp;9.8</a></td>
     1385                  <td class="left"><a href="#header.retry-after" id="rfc.xref.header.retry-after.1" title="Retry-After">Section&nbsp;9.16</a></td>
    13861386               </tr>
    13871387               <tr>
    13881388                  <td class="left">Server</td>
    1389                   <td class="left"><a href="#header.server" id="rfc.xref.header.server.1" title="Server">Section&nbsp;9.9</a></td>
     1389                  <td class="left"><a href="#header.server" id="rfc.xref.header.server.1" title="Server">Section&nbsp;9.17</a></td>
    13901390               </tr>
    13911391               <tr>
    … …  
    14241424      </ul>
    14251425      <p id="rfc.section.4.p.6">For most status codes the response can carry a payload, in which case a Content-Type header field indicates the payload's
    1426          media type (<a href="#header.content-type" id="rfc.xref.header.content-type.2" title="Content-Type">Section&nbsp;9.18</a>).
     1426         media type (<a href="#header.content-type" id="rfc.xref.header.content-type.2" title="Content-Type">Section&nbsp;9.9</a>).
    14271427      </p>
    14281428      <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;<a id="overview.of.status.codes" href="#overview.of.status.codes">Overview of Status Codes</a></h2>
    … …  
    18201820         </p>
    18211821      </div>
    1822       <p id="rfc.section.4.5.p.4">A Location header field on a 3xx response indicates that a client <em class="bcp14">MAY</em> automatically redirect to the URI provided; see <a href="#header.location" id="rfc.xref.header.location.3" title="Location">Section&nbsp;9.5</a>.
     1822      <p id="rfc.section.4.5.p.4">A Location header field on a 3xx response indicates that a client <em class="bcp14">MAY</em> automatically redirect to the URI provided; see <a href="#header.location" id="rfc.xref.header.location.3" title="Location">Section&nbsp;9.13</a>.
    18231823      </p>
    18241824      <p id="rfc.section.4.5.p.5">Note that for methods not known to be "safe", as defined in <a href="#safe.methods" title="Safe Methods">Section&nbsp;2.1.1</a>, automatic redirection needs to done with care, since the redirect might change the conditions under which the request was
    … …  
    20362036      <div id="rfc.iref.s.31"></div>
    20372037      <h3 id="rfc.section.4.6.14"><a href="#rfc.section.4.6.14">4.6.14</a>&nbsp;<a id="status.417" href="#status.417">417 Expectation Failed</a></h3>
    2038       <p id="rfc.section.4.6.14.p.1">The expectation given in an Expect header field (see <a href="#header.expect" id="rfc.xref.header.expect.2" title="Expect">Section&nbsp;9.3</a>) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could
     2038      <p id="rfc.section.4.6.14.p.1">The expectation given in an Expect header field (see <a href="#header.expect" id="rfc.xref.header.expect.2" title="Expect">Section&nbsp;9.11</a>) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could
    20392039         not be met by the next-hop server.
    20402040      </p>
    … …  
    20812081      <p id="rfc.section.4.7.4.p.1">The server is currently unable to handle the request due to a temporary overloading or maintenance of the server.</p>
    20822082      <p id="rfc.section.4.7.4.p.2">The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the
    2083          delay <em class="bcp14">MAY</em> be indicated in a Retry-After header field (<a href="#header.retry-after" id="rfc.xref.header.retry-after.2" title="Retry-After">Section&nbsp;9.8</a>). If no Retry-After is given, the client <em class="bcp14">SHOULD</em> handle the response as it would for a 500 response.
     2083         delay <em class="bcp14">MAY</em> be indicated in a Retry-After header field (<a href="#header.retry-after" id="rfc.xref.header.retry-after.2" title="Retry-After">Section&nbsp;9.16</a>). If no Retry-After is given, the client <em class="bcp14">SHOULD</em> handle the response as it would for a 500 response.
    20842084      </p>
    20852085      <div class="note" id="rfc.section.4.7.4.p.3">
    … …  
    22282228      </p>
    22292229      <div id="rfc.figure.u.19"></div><pre class="inline"><span id="rfc.iref.g.25"></span>  <a href="#content.codings" class="smpl">content-coding</a>   = <a href="#core.rules" class="smpl">token</a>
    2230 </pre><p id="rfc.section.5.4.p.3">All content-coding values are case-insensitive. HTTP/1.1 uses content-coding values in the Accept-Encoding (<a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.2" title="Accept-Encoding">Section&nbsp;9.13</a>) and Content-Encoding (<a href="#header.content-encoding" id="rfc.xref.header.content-encoding.1" title="Content-Encoding">Section&nbsp;9.15</a>) header fields. Although the value describes the content-coding, what is more important is that it indicates what decoding
     2230</pre><p id="rfc.section.5.4.p.3">All content-coding values are case-insensitive. HTTP/1.1 uses content-coding values in the Accept-Encoding (<a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.2" title="Accept-Encoding">Section&nbsp;9.3</a>) and Content-Encoding (<a href="#header.content-encoding" id="rfc.xref.header.content-encoding.1" title="Content-Encoding">Section&nbsp;9.6</a>) header fields. Although the value describes the content-coding, what is more important is that it indicates what decoding
    22312231         mechanism will be required to remove the encoding.
    22322232      </p>
    … …  
    22652265      </p>
    22662266      <h2 id="rfc.section.5.5"><a href="#rfc.section.5.5">5.5</a>&nbsp;<a id="media.types" href="#media.types">Media Types</a></h2>
    2267       <p id="rfc.section.5.5.p.1">HTTP uses Internet Media Types <a href="#RFC2046" id="rfc.xref.RFC2046.1"><cite title="Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types">[RFC2046]</cite></a> in the Content-Type (<a href="#header.content-type" id="rfc.xref.header.content-type.3" title="Content-Type">Section&nbsp;9.18</a>) and Accept (<a href="#header.accept" id="rfc.xref.header.accept.2" title="Accept">Section&nbsp;9.11</a>) header fields in order to provide open and extensible data typing and type negotiation.
     2267      <p id="rfc.section.5.5.p.1">HTTP uses Internet Media Types <a href="#RFC2046" id="rfc.xref.RFC2046.1"><cite title="Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types">[RFC2046]</cite></a> in the Content-Type (<a href="#header.content-type" id="rfc.xref.header.content-type.3" title="Content-Type">Section&nbsp;9.9</a>) and Accept (<a href="#header.accept" id="rfc.xref.header.accept.2" title="Accept">Section&nbsp;9.1</a>) header fields in order to provide open and extensible data typing and type negotiation.
    22682268      </p>
    22692269      <div id="rfc.figure.u.20"></div><pre class="inline"><span id="rfc.iref.g.27"></span><span id="rfc.iref.g.28"></span><span id="rfc.iref.g.29"></span>  <a href="#media.types" class="smpl">media-type</a> = <a href="#media.types" class="smpl">type</a> "/" <a href="#media.types" class="smpl">subtype</a> *( <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> <a href="#rule.parameter" class="smpl">parameter</a> )
    … …  
    24362436               <tr>
    24372437                  <td class="left">Content-Encoding</td>
    2438                   <td class="left"><a href="#header.content-encoding" id="rfc.xref.header.content-encoding.2" title="Content-Encoding">Section&nbsp;9.15</a></td>
     2438                  <td class="left"><a href="#header.content-encoding" id="rfc.xref.header.content-encoding.2" title="Content-Encoding">Section&nbsp;9.6</a></td>
    24392439               </tr>
    24402440               <tr>
    24412441                  <td class="left">Content-Language</td>
    2442                   <td class="left"><a href="#header.content-language" id="rfc.xref.header.content-language.1" title="Content-Language">Section&nbsp;9.16</a></td>
     2442                  <td class="left"><a href="#header.content-language" id="rfc.xref.header.content-language.1" title="Content-Language">Section&nbsp;9.7</a></td>
    24432443               </tr>
    24442444               <tr>
    24452445                  <td class="left">Content-Location</td>
    2446                   <td class="left"><a href="#header.content-location" id="rfc.xref.header.content-location.2" title="Content-Location">Section&nbsp;9.17</a></td>
     2446                  <td class="left"><a href="#header.content-location" id="rfc.xref.header.content-location.2" title="Content-Location">Section&nbsp;9.8</a></td>
    24472447               </tr>
    24482448               <tr>
    24492449                  <td class="left">Content-Type</td>
    2450                   <td class="left"><a href="#header.content-type" id="rfc.xref.header.content-type.4" title="Content-Type">Section&nbsp;9.18</a></td>
     2450                  <td class="left"><a href="#header.content-type" id="rfc.xref.header.content-type.4" title="Content-Type">Section&nbsp;9.9</a></td>
    24512451               </tr>
    24522452               <tr>
    … …  
    25612561      </p>
    25622562      <p id="rfc.section.8.1.p.6">HTTP/1.1 includes the following header fields for enabling server-driven negotiation through description of user agent capabilities
    2563          and user preferences: Accept (<a href="#header.accept" id="rfc.xref.header.accept.3" title="Accept">Section&nbsp;9.11</a>), Accept-Charset (<a href="#header.accept-charset" id="rfc.xref.header.accept-charset.2" title="Accept-Charset">Section&nbsp;9.12</a>), Accept-Encoding (<a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.3" title="Accept-Encoding">Section&nbsp;9.13</a>), Accept-Language (<a href="#header.accept-language" id="rfc.xref.header.accept-language.2" title="Accept-Language">Section&nbsp;9.14</a>), and User-Agent (<a href="#header.user-agent" id="rfc.xref.header.user-agent.2" title="User-Agent">Section&nbsp;9.10</a>). However, an origin server is not limited to these dimensions and <em class="bcp14">MAY</em> vary the response based on any aspect of the request, including aspects of the connection (e.g., IP address) or information
     2563         and user preferences: Accept (<a href="#header.accept" id="rfc.xref.header.accept.3" title="Accept">Section&nbsp;9.1</a>), Accept-Charset (<a href="#header.accept-charset" id="rfc.xref.header.accept-charset.2" title="Accept-Charset">Section&nbsp;9.2</a>), Accept-Encoding (<a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.3" title="Accept-Encoding">Section&nbsp;9.3</a>), Accept-Language (<a href="#header.accept-language" id="rfc.xref.header.accept-language.2" title="Accept-Language">Section&nbsp;9.4</a>), and User-Agent (<a href="#header.user-agent" id="rfc.xref.header.user-agent.2" title="User-Agent">Section&nbsp;9.18</a>). However, an origin server is not limited to these dimensions and <em class="bcp14">MAY</em> vary the response based on any aspect of the request, including aspects of the connection (e.g., IP address) or information
    25642564         within extension header fields not defined by this specification.
    25652565      </p>
    … …  
    25952595      <div id="rfc.iref.a.1"></div>
    25962596      <div id="rfc.iref.h.2"></div>
    2597       <h2 id="rfc.section.9.1"><a href="#rfc.section.9.1">9.1</a>&nbsp;<a id="header.allow" href="#header.allow">Allow</a></h2>
    2598       <p id="rfc.section.9.1.p.1">The "Allow" header field lists the set of methods advertised as supported by the target resource. The purpose of this field
     2597      <h2 id="rfc.section.9.1"><a href="#rfc.section.9.1">9.1</a>&nbsp;<a id="header.accept" href="#header.accept">Accept</a></h2>
     2598      <p id="rfc.section.9.1.p.1">The "Accept" header field can be used by user agents to specify response media types that are acceptable. Accept header fields
     2599         can be used to indicate that the request is specifically limited to a small set of desired types, as in the case of a request
     2600         for an in-line image.
     2601      </p>
     2602      <div id="rfc.figure.u.25"></div><pre class="inline"><span id="rfc.iref.g.34"></span><span id="rfc.iref.g.35"></span><span id="rfc.iref.g.36"></span><span id="rfc.iref.g.37"></span>  <a href="#header.accept" class="smpl">Accept</a> = #( <a href="#header.accept" class="smpl">media-range</a> [ <a href="#header.accept" class="smpl">accept-params</a> ] )
     2603 
     2604  <a href="#header.accept" class="smpl">media-range</a>    = ( "*/*"
     2605                   / ( <a href="#media.types" class="smpl">type</a> "/" "*" )
     2606                   / ( <a href="#media.types" class="smpl">type</a> "/" <a href="#media.types" class="smpl">subtype</a> )
     2607                   ) *( <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> <a href="#rule.parameter" class="smpl">parameter</a> )
     2608  <a href="#header.accept" class="smpl">accept-params</a>  = <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> "q=" <a href="#abnf.dependencies" class="smpl">qvalue</a> *( <a href="#header.accept" class="smpl">accept-ext</a> )
     2609  <a href="#header.accept" class="smpl">accept-ext</a>     = <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> <a href="#core.rules" class="smpl">token</a> [ "=" <a href="#core.rules" class="smpl">word</a> ]
     2610</pre><p id="rfc.section.9.1.p.3">The asterisk "*" character is used to group media types into ranges, with "*/*" indicating all media types and "type/*" indicating
     2611         all subtypes of that type. The media-range <em class="bcp14">MAY</em> include media type parameters that are applicable to that range.
     2612      </p>
     2613      <p id="rfc.section.9.1.p.4">Each media-range <em class="bcp14">MAY</em> be followed by one or more accept-params, beginning with the "q" parameter for indicating a relative quality factor. The first
     2614         "q" parameter (if any) separates the media-range parameter(s) from the accept-params. Quality factors allow the user or user
     2615         agent to indicate the relative degree of preference for that media-range, using the qvalue scale from 0 to 1 (qvalue;). The
     2616         default value is q=1.
     2617      </p>
     2618      <div class="note" id="rfc.section.9.1.p.5">
     2619         <p> <b>Note:</b> Use of the "q" parameter name to separate media type parameters from Accept extension parameters is due to historical practice.
     2620            Although this prevents any media type parameter named "q" from being used with a media range, such an event is believed to
     2621            be unlikely given the lack of any "q" parameters in the IANA media type registry and the rare usage of any media type parameters
     2622            in Accept. Future media types are discouraged from registering any parameter named "q".
     2623         </p>
     2624      </div>
     2625      <p id="rfc.section.9.1.p.6">The example</p>
     2626      <div id="rfc.figure.u.26"></div><pre class="text">  Accept: audio/*; q=0.2, audio/basic
     2627</pre><p id="rfc.section.9.1.p.8"> <em class="bcp14">SHOULD</em> be interpreted as "I prefer audio/basic, but send me any audio type if it is the best available after an 80% mark-down in
     2628         quality".
     2629      </p>
     2630      <p id="rfc.section.9.1.p.9">A request without any Accept header field implies that the user agent will accept any media type in response. If an Accept
     2631         header field is present in a request and none of the available representations for the response have a media type that is
     2632         listed as acceptable, the origin server <em class="bcp14">MAY</em> either honor the Accept header field by sending a 406 (Not Acceptable) response or disregard the Accept header field by treating
     2633         the response as if it is not subject to content negotiation.
     2634      </p>
     2635      <p id="rfc.section.9.1.p.10">A more elaborate example is</p>
     2636      <div id="rfc.figure.u.27"></div><pre class="text">  Accept: text/plain; q=0.5, text/html,
     2637          text/x-dvi; q=0.8, text/x-c
     2638</pre><p id="rfc.section.9.1.p.12">Verbally, this would be interpreted as "text/html and text/x-c are the preferred media types, but if they do not exist, then
     2639         send the text/x-dvi representation, and if that does not exist, send the text/plain representation".
     2640      </p>
     2641      <p id="rfc.section.9.1.p.13">Media ranges can be overridden by more specific media ranges or specific media types. If more than one media range applies
     2642         to a given type, the most specific reference has precedence. For example,
     2643      </p>
     2644      <div id="rfc.figure.u.28"></div><pre class="text">  Accept: text/*, text/plain, text/plain;format=flowed, */*
     2645</pre><p id="rfc.section.9.1.p.15">have the following precedence: </p>
     2646      <ol>
     2647         <li>text/plain;format=flowed</li>
     2648         <li>text/plain</li>
     2649         <li>text/*</li>
     2650         <li>*/*</li>
     2651      </ol>
     2652      <p id="rfc.section.9.1.p.16">The media type quality factor associated with a given type is determined by finding the media range with the highest precedence
     2653         which matches that type. For example,
     2654      </p>
     2655      <div id="rfc.figure.u.29"></div><pre class="text">  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
     2656          text/html;level=2;q=0.4, */*;q=0.5
     2657</pre><p id="rfc.section.9.1.p.18">would cause the following values to be associated:</p>
     2658      <div id="rfc.table.u.7">
     2659         <table class="tt full left" cellpadding="3" cellspacing="0">
     2660            <thead>
     2661               <tr>
     2662                  <th>Media Type</th>
     2663                  <th>Quality Value</th>
     2664               </tr>
     2665            </thead>
     2666            <tbody>
     2667               <tr>
     2668                  <td class="left">text/html;level=1</td>
     2669                  <td class="left">1</td>
     2670               </tr>
     2671               <tr>
     2672                  <td class="left">text/html</td>
     2673                  <td class="left">0.7</td>
     2674               </tr>
     2675               <tr>
     2676                  <td class="left">text/plain</td>
     2677                  <td class="left">0.3</td>
     2678               </tr>
     2679               <tr>
     2680                  <td class="left">image/jpeg</td>
     2681                  <td class="left">0.5</td>
     2682               </tr>
     2683               <tr>
     2684                  <td class="left">text/html;level=2</td>
     2685                  <td class="left">0.4</td>
     2686               </tr>
     2687               <tr>
     2688                  <td class="left">text/html;level=3</td>
     2689                  <td class="left">0.7</td>
     2690               </tr>
     2691            </tbody>
     2692         </table>
     2693      </div>
     2694      <p id="rfc.section.9.1.p.19"> <b>Note:</b> A user agent might be provided with a default set of quality values for certain media ranges. However, unless the user agent
     2695         is a closed system which cannot interact with other rendering agents, this default set ought to be configurable by the user.
     2696      </p>
     2697      <div id="rfc.iref.a.2"></div>
     2698      <div id="rfc.iref.h.3"></div>
     2699      <h2 id="rfc.section.9.2"><a href="#rfc.section.9.2">9.2</a>&nbsp;<a id="header.accept-charset" href="#header.accept-charset">Accept-Charset</a></h2>
     2700      <p id="rfc.section.9.2.p.1">The "Accept-Charset" header field can be used by user agents to indicate what character encodings are acceptable in a response
     2701         payload. This field allows clients capable of understanding more comprehensive or special-purpose character encodings to signal
     2702         that capability to a server which is capable of representing documents in those character encodings.
     2703      </p>
     2704      <div id="rfc.figure.u.30"></div><pre class="inline"><span id="rfc.iref.g.38"></span>  <a href="#header.accept-charset" class="smpl">Accept-Charset</a> = 1#( ( <a href="#rule.charset" class="smpl">charset</a> / "*" )
     2705                         [ <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> "q=" <a href="#abnf.dependencies" class="smpl">qvalue</a> ] )
     2706</pre><p id="rfc.section.9.2.p.3">Character encoding values (a.k.a., charsets) are described in <a href="#character.sets" title="Character Encodings (charset)">Section&nbsp;5.3</a>. Each charset <em class="bcp14">MAY</em> be given an associated quality value which represents the user's preference for that charset. The default value is q=1. An
     2707         example is
     2708      </p>
     2709      <div id="rfc.figure.u.31"></div><pre class="text">  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
     2710</pre><p id="rfc.section.9.2.p.5">The special value "*", if present in the Accept-Charset field, matches every character encoding which is not mentioned elsewhere
     2711         in the Accept-Charset field. If no "*" is present in an Accept-Charset field, then all character encodings not explicitly
     2712         mentioned get a quality value of 0.
     2713      </p>
     2714      <p id="rfc.section.9.2.p.6">A request without any Accept-Charset header field implies that the user agent will accept any character encoding in response.
     2715         If an Accept-Charset header field is present in a request and none of the available representations for the response have
     2716         a character encoding that is listed as acceptable, the origin server <em class="bcp14">MAY</em> either honor the Accept-Charset header field by sending a 406 (Not Acceptable) response or disregard the Accept-Charset header
     2717         field by treating the response as if it is not subject to content negotiation.
     2718      </p>
     2719      <div id="rfc.iref.a.3"></div>
     2720      <div id="rfc.iref.h.4"></div>
     2721      <h2 id="rfc.section.9.3"><a href="#rfc.section.9.3">9.3</a>&nbsp;<a id="header.accept-encoding" href="#header.accept-encoding">Accept-Encoding</a></h2>
     2722      <p id="rfc.section.9.3.p.1">The "Accept-Encoding" header field can be used by user agents to indicate what response content-codings (<a href="#content.codings" title="Content Codings">Section&nbsp;5.4</a>) are acceptable in the response. An "identity" token is used as a synonym for "no encoding" in order to communicate when
     2723         no encoding is preferred.
     2724      </p>
     2725      <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.39"></span><span id="rfc.iref.g.40"></span>  <a href="#header.accept-encoding" class="smpl">Accept-Encoding</a>  = #( <a href="#header.accept-encoding" class="smpl">codings</a> [ <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> "q=" <a href="#abnf.dependencies" class="smpl">qvalue</a> ] )
     2726  <a href="#header.accept-encoding" class="smpl">codings</a>          = <a href="#content.codings" class="smpl">content-coding</a> / "identity" / "*"
     2727</pre><p id="rfc.section.9.3.p.3">Each codings value <em class="bcp14">MAY</em> be given an associated quality value which represents the preference for that encoding. The default value is q=1.
     2728      </p>
     2729      <p id="rfc.section.9.3.p.4">For example,</p>
     2730      <div id="rfc.figure.u.33"></div><pre class="text">  Accept-Encoding: compress, gzip
     2731  Accept-Encoding:
     2732  Accept-Encoding: *
     2733  Accept-Encoding: compress;q=0.5, gzip;q=1.0
     2734  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
     2735</pre><p id="rfc.section.9.3.p.6">A server tests whether a content-coding for a given representation is acceptable, according to an Accept-Encoding field, using
     2736         these rules:
     2737      </p>
     2738      <ol>
     2739         <li>The special "*" symbol in an Accept-Encoding field matches any available content-coding not explicitly listed in the header
     2740            field.
     2741         </li>
     2742         <li>If the representation has no content-coding, then it is acceptable by default unless specifically excluded by the Accept-Encoding
     2743            field stating either "identity;q=0" or "*;q=0" without a more specific entry for "identity".
     2744         </li>
     2745         <li>If the representation's content-coding is one of the content-codings listed in the Accept-Encoding field, then it is acceptable
     2746            unless it is accompanied by a qvalue of 0. (As defined in qvalue;, a qvalue of 0 means "not acceptable".)
     2747         </li>
     2748         <li>If multiple content-codings are acceptable, then the acceptable content-coding with the highest non-zero qvalue is preferred.</li>
     2749      </ol>
     2750      <p id="rfc.section.9.3.p.7">An Accept-Encoding header field with a combined field-value that is empty implies that the user agent does not want any content-coding
     2751         in response. If an Accept-Encoding header field is present in a request and none of the available representations for the
     2752         response have a content-coding that is listed as acceptable, the origin server <em class="bcp14">SHOULD</em> send a response without any content-coding.
     2753      </p>
     2754      <p id="rfc.section.9.3.p.8">A request without an Accept-Encoding header field implies that the user agent will accept any content-coding in response,
     2755         but a representation without content-coding is preferred for compatibility with the widest variety of user agents.
     2756      </p>
     2757      <div class="note" id="rfc.section.9.3.p.9">
     2758         <p> <b>Note:</b> Most HTTP/1.0 applications do not recognize or obey qvalues associated with content-codings. This means that qvalues will
     2759            not work and are not permitted with x-gzip or x-compress.
     2760         </p>
     2761      </div>
     2762      <div id="rfc.iref.a.4"></div>
     2763      <div id="rfc.iref.h.5"></div>
     2764      <h2 id="rfc.section.9.4"><a href="#rfc.section.9.4">9.4</a>&nbsp;<a id="header.accept-language" href="#header.accept-language">Accept-Language</a></h2>
     2765      <p id="rfc.section.9.4.p.1">The "Accept-Language" header field can be used by user agents to indicate the set of natural languages that are preferred
     2766         in the response. Language tags are defined in <a href="#language.tags" title="Language Tags">Section&nbsp;5.6</a>.
     2767      </p>
     2768      <div id="rfc.figure.u.34"></div><pre class="inline"><span id="rfc.iref.g.41"></span><span id="rfc.iref.g.42"></span>  <a href="#header.accept-language" class="smpl">Accept-Language</a> =
     2769                    1#( <a href="#header.accept-language" class="smpl">language-range</a> [ <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> "q=" <a href="#abnf.dependencies" class="smpl">qvalue</a> ] )
     2770  <a href="#header.accept-language" class="smpl">language-range</a>  =
     2771            &lt;language-range, defined in <a href="#RFC4647" id="rfc.xref.RFC4647.1"><cite title="Matching of Language Tags">[RFC4647]</cite></a>, <a href="http://tools.ietf.org/html/rfc4647#section-2.1">Section 2.1</a>&gt;
     2772</pre><p id="rfc.section.9.4.p.3">Each language-range can be given an associated quality value which represents an estimate of the user's preference for the
     2773         languages specified by that range. The quality value defaults to "q=1". For example,
     2774      </p>
     2775      <div id="rfc.figure.u.35"></div><pre class="text">  Accept-Language: da, en-gb;q=0.8, en;q=0.7
     2776</pre><p id="rfc.section.9.4.p.5">would mean: "I prefer Danish, but will accept British English and other types of English". (see also <a href="http://tools.ietf.org/html/rfc4647#section-2.3">Section 2.3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.2"><cite title="Matching of Language Tags">[RFC4647]</cite></a>)
     2777      </p>
     2778      <p id="rfc.section.9.4.p.6">For matching, <a href="http://tools.ietf.org/html/rfc4647#section-3">Section 3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.3"><cite title="Matching of Language Tags">[RFC4647]</cite></a> defines several matching schemes. Implementations can offer the most appropriate matching scheme for their requirements.
     2779      </p>
     2780      <div class="note" id="rfc.section.9.4.p.7">
     2781         <p> <b>Note:</b> The "Basic Filtering" scheme (<a href="#RFC4647" id="rfc.xref.RFC4647.4"><cite title="Matching of Language Tags">[RFC4647]</cite></a>, <a href="http://tools.ietf.org/html/rfc4647#section-3.3.1">Section 3.3.1</a>) is identical to the matching scheme that was previously defined in <a href="http://tools.ietf.org/html/rfc2616#section-14.4">Section 14.4</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
     2782         </p>
     2783      </div>
     2784      <p id="rfc.section.9.4.p.8">It might be contrary to the privacy expectations of the user to send an Accept-Language header field with the complete linguistic
     2785         preferences of the user in every request. For a discussion of this issue, see <a href="#privacy.issues.connected.to.accept.header.fields" title="Privacy Issues Connected to Accept Header Fields">Section&nbsp;11.5</a>.
     2786      </p>
     2787      <p id="rfc.section.9.4.p.9">As intelligibility is highly dependent on the individual user, it is recommended that client applications make the choice
     2788         of linguistic preference available to the user. If the choice is not made available, then the Accept-Language header field <em class="bcp14">MUST NOT</em> be given in the request.
     2789      </p>
     2790      <div class="note" id="rfc.section.9.4.p.10">
     2791         <p> <b>Note:</b> When making the choice of linguistic preference available to the user, we remind implementors of the fact that users are not
     2792            familiar with the details of language matching as described above, and ought to be provided appropriate guidance. As an example,
     2793            users might assume that on selecting "en-gb", they will be served any kind of English document if British English is not available.
     2794            A user agent might suggest in such a case to add "en" to get the best matching behavior.
     2795         </p>
     2796      </div>
     2797      <div id="rfc.iref.a.5"></div>
     2798      <div id="rfc.iref.h.6"></div>
     2799      <h2 id="rfc.section.9.5"><a href="#rfc.section.9.5">9.5</a>&nbsp;<a id="header.allow" href="#header.allow">Allow</a></h2>
     2800      <p id="rfc.section.9.5.p.1">The "Allow" header field lists the set of methods advertised as supported by the target resource. The purpose of this field
    25992801         is strictly to inform the recipient of valid request methods associated with the resource.
    26002802      </p>
    2601       <div id="rfc.figure.u.25"></div><pre class="inline"><span id="rfc.iref.g.34"></span>  <a href="#header.allow" class="smpl">Allow</a> = #<a href="#methods" class="smpl">method</a>
    2602 </pre><p id="rfc.section.9.1.p.3">Example of use:</p>
    2603       <div id="rfc.figure.u.26"></div><pre class="text">  Allow: GET, HEAD, PUT
    2604 </pre><p id="rfc.section.9.1.p.5">The actual set of allowed methods is defined by the origin server at the time of each request.</p>
    2605       <p id="rfc.section.9.1.p.6">A proxy <em class="bcp14">MUST NOT</em> modify the Allow header field — it does not need to understand all the methods specified in order to handle them according
     2803      <div id="rfc.figure.u.36"></div><pre class="inline"><span id="rfc.iref.g.43"></span>  <a href="#header.allow" class="smpl">Allow</a> = #<a href="#methods" class="smpl">method</a>
     2804</pre><p id="rfc.section.9.5.p.3">Example of use:</p>
     2805      <div id="rfc.figure.u.37"></div><pre class="text">  Allow: GET, HEAD, PUT
     2806</pre><p id="rfc.section.9.5.p.5">The actual set of allowed methods is defined by the origin server at the time of each request.</p>
     2807      <p id="rfc.section.9.5.p.6">A proxy <em class="bcp14">MUST NOT</em> modify the Allow header field — it does not need to understand all the methods specified in order to handle them according
    26062808         to the generic message handling rules.
    26072809      </p>
     2810      <div id="rfc.iref.c.7"></div>
     2811      <div id="rfc.iref.h.7"></div>
     2812      <h2 id="rfc.section.9.6"><a href="#rfc.section.9.6">9.6</a>&nbsp;<a id="header.content-encoding" href="#header.content-encoding">Content-Encoding</a></h2>
     2813      <p id="rfc.section.9.6.p.1">The "Content-Encoding" header field indicates what content-codings have been applied to the representation beyond those inherent
     2814         in the media type, and thus what decoding mechanisms have to be applied in order to obtain the media-type referenced by the
     2815         Content-Type header field. Content-Encoding is primarily used to allow a representation to be compressed without losing the
     2816         identity of its underlying media type.
     2817      </p>
     2818      <div id="rfc.figure.u.38"></div><pre class="inline"><span id="rfc.iref.g.44"></span>  <a href="#header.content-encoding" class="smpl">Content-Encoding</a> = 1#<a href="#content.codings" class="smpl">content-coding</a>
     2819</pre><p id="rfc.section.9.6.p.3">Content codings are defined in <a href="#content.codings" title="Content Codings">Section&nbsp;5.4</a>. An example of its use is
     2820      </p>
     2821      <div id="rfc.figure.u.39"></div><pre class="text">  Content-Encoding: gzip
     2822</pre><p id="rfc.section.9.6.p.5">The content-coding is a characteristic of the representation. Typically, the representation body is stored with this encoding
     2823         and is only decoded before rendering or analogous usage. However, a transforming proxy <em class="bcp14">MAY</em> modify the content-coding if the new coding is known to be acceptable to the recipient, unless the "no-transform" cache-control
     2824         directive is present in the message.
     2825      </p>
     2826      <p id="rfc.section.9.6.p.6">If the media type includes an inherent encoding, such as a data format that is always compressed, then that encoding would
     2827         not be restated as a Content-Encoding even if it happens to be the same algorithm as one of the content-codings. Such a content-coding
     2828         would only be listed if, for some bizarre reason, it is applied a second time to form the representation. Likewise, an origin
     2829         server might choose to publish the same payload data as multiple representations that differ only in whether the coding is
     2830         defined as part of Content-Type or Content-Encoding, since some user agents will behave differently in their handling of each
     2831         response (e.g., open a "Save as ..." dialog instead of automatic decompression and rendering of content).
     2832      </p>
     2833      <p id="rfc.section.9.6.p.7">A representation that has a content-coding applied to it <em class="bcp14">MUST</em> include a Content-Encoding header field (<a href="#header.content-encoding" id="rfc.xref.header.content-encoding.3" title="Content-Encoding">Section&nbsp;9.6</a>) that lists the content-coding(s) applied.
     2834      </p>
     2835      <p id="rfc.section.9.6.p.8">If multiple encodings have been applied to a representation, the content codings <em class="bcp14">MUST</em> be listed in the order in which they were applied. Additional information about the encoding parameters <em class="bcp14">MAY</em> be provided by other header fields not defined by this specification.
     2836      </p>
     2837      <p id="rfc.section.9.6.p.9">If the content-coding of a representation in a request message is not acceptable to the origin server, the server <em class="bcp14">SHOULD</em> respond with a status code of 415 (Unsupported Media Type).
     2838      </p>
     2839      <div id="rfc.iref.c.8"></div>
     2840      <div id="rfc.iref.h.8"></div>
     2841      <h2 id="rfc.section.9.7"><a href="#rfc.section.9.7">9.7</a>&nbsp;<a id="header.content-language" href="#header.content-language">Content-Language</a></h2>
     2842      <p id="rfc.section.9.7.p.1">The "Content-Language" header field describes the natural language(s) of the intended audience for the representation. Note
     2843         that this might not be equivalent to all the languages used within the representation.
     2844      </p>
     2845      <div id="rfc.figure.u.40"></div><pre class="inline"><span id="rfc.iref.g.45"></span>  <a href="#header.content-language" class="smpl">Content-Language</a> = 1#<a href="#language.tags" class="smpl">language-tag</a>
     2846</pre><p id="rfc.section.9.7.p.3">Language tags are defined in <a href="#language.tags" title="Language Tags">Section&nbsp;5.6</a>. The primary purpose of Content-Language is to allow a user to identify and differentiate representations according to the
     2847         user's own preferred language. Thus, if the body content is intended only for a Danish-literate audience, the appropriate
     2848         field is
     2849      </p>
     2850      <div id="rfc.figure.u.41"></div><pre class="text">  Content-Language: da
     2851</pre><p id="rfc.section.9.7.p.5">If no Content-Language is specified, the default is that the content is intended for all language audiences. This might mean
     2852         that the sender does not consider it to be specific to any natural language, or that the sender does not know for which language
     2853         it is intended.
     2854      </p>
     2855      <p id="rfc.section.9.7.p.6">Multiple languages <em class="bcp14">MAY</em> be listed for content that is intended for multiple audiences. For example, a rendition of the "Treaty of Waitangi", presented
     2856         simultaneously in the original Maori and English versions, would call for
     2857      </p>
     2858      <div id="rfc.figure.u.42"></div><pre class="text">  Content-Language: mi, en
     2859</pre><p id="rfc.section.9.7.p.8">However, just because multiple languages are present within a representation does not mean that it is intended for multiple
     2860         linguistic audiences. An example would be a beginner's language primer, such as "A First Lesson in Latin", which is clearly
     2861         intended to be used by an English-literate audience. In this case, the Content-Language would properly only include "en".
     2862      </p>
     2863      <p id="rfc.section.9.7.p.9">Content-Language <em class="bcp14">MAY</em> be applied to any media type — it is not limited to textual documents.
     2864      </p>
     2865      <div id="rfc.iref.c.9"></div>
     2866      <div id="rfc.iref.h.9"></div>
     2867      <h2 id="rfc.section.9.8"><a href="#rfc.section.9.8">9.8</a>&nbsp;<a id="header.content-location" href="#header.content-location">Content-Location</a></h2>
     2868      <p id="rfc.section.9.8.p.1">The "Content-Location" header field supplies a URI that can be used as a specific identifier for the representation in this
     2869         message. In other words, if one were to perform a GET on this URI at the time of this message's generation, then a 200 response
     2870         would contain the same representation that is enclosed as payload in this message.
     2871      </p>
     2872      <div id="rfc.figure.u.43"></div><pre class="inline"><span id="rfc.iref.g.46"></span>  <a href="#header.content-location" class="smpl">Content-Location</a> = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a>
     2873</pre><p id="rfc.section.9.8.p.3">The Content-Location value is not a replacement for the effective Request URI (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.47"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). It is representation metadata. It has the same syntax and semantics as the header field of the same name defined for MIME
     2874         body parts in <a href="http://tools.ietf.org/html/rfc2557#section-4">Section 4</a> of <a href="#RFC2557" id="rfc.xref.RFC2557.1"><cite title="MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)">[RFC2557]</cite></a>. However, its appearance in an HTTP message has some special implications for HTTP recipients.
     2875      </p>
     2876      <p id="rfc.section.9.8.p.4">If Content-Location is included in a response message and its value is the same as the effective request URI, then the response
     2877         payload <em class="bcp14">SHOULD</em> be considered a current representation of that resource. For a GET or HEAD request, this is the same as the default semantics
     2878         when no Content-Location is provided by the server. For a state-changing request like PUT or POST, it implies that the server's
     2879         response contains the new representation of that resource, thereby distinguishing it from representations that might only
     2880         report about the action (e.g., "It worked!"). This allows authoring applications to update their local copies without the
     2881         need for a subsequent GET request.
     2882      </p>
     2883      <p id="rfc.section.9.8.p.5">If Content-Location is included in a response message and its value differs from the effective request URI, then the origin
     2884         server is informing recipients that this representation has its own, presumably more specific, identifier. For a GET or HEAD
     2885         request, this is an indication that the effective request URI identifies a resource that is subject to content negotiation
     2886         and the selected representation for this response can also be found at the identified URI. For other methods, such a Content-Location
     2887         indicates that this representation contains a report on the action's status and the same report is available (for future access
     2888         with GET) at the given URI. For example, a purchase transaction made via a POST request might include a receipt document as
     2889         the payload of the 200 response; the Content-Location value provides an identifier for retrieving a copy of that same receipt
     2890         in the future.
     2891      </p>
     2892      <p id="rfc.section.9.8.p.6">If Content-Location is included in a request message, then it <em class="bcp14">MAY</em> be interpreted by the origin server as an indication of where the user agent originally obtained the content of the enclosed
     2893         representation (prior to any subsequent modification of the content by that user agent). In other words, the user agent is
     2894         providing the same representation metadata that it received with the original representation. However, such interpretation <em class="bcp14">MUST NOT</em> be used to alter the semantics of the method requested by the client. For example, if a client makes a PUT request on a negotiated
     2895         resource and the origin server accepts that PUT (without redirection), then the new set of values for that resource is expected
     2896         to be consistent with the one representation supplied in that PUT; the Content-Location cannot be used as a form of reverse
     2897         content selection that identifies only one of the negotiated representations to be updated. If the user agent had wanted the
     2898         latter semantics, it would have applied the PUT directly to the Content-Location URI.
     2899      </p>
     2900      <p id="rfc.section.9.8.p.7">A Content-Location field received in a request message is transitory information that <em class="bcp14">SHOULD NOT</em> be saved with other representation metadata for use in later responses. The Content-Location's value might be saved for use
     2901         in other contexts, such as within source links or other metadata.
     2902      </p>
     2903      <p id="rfc.section.9.8.p.8">A cache cannot assume that a representation with a Content-Location different from the URI used to retrieve it can be used
     2904         to respond to later requests on that Content-Location URI.
     2905      </p>
     2906      <p id="rfc.section.9.8.p.9">If the Content-Location value is a partial URI, the partial URI is interpreted relative to the effective request URI.</p>
     2907      <div id="rfc.iref.c.10"></div>
     2908      <div id="rfc.iref.h.10"></div>
     2909      <h2 id="rfc.section.9.9"><a href="#rfc.section.9.9">9.9</a>&nbsp;<a id="header.content-type" href="#header.content-type">Content-Type</a></h2>
     2910      <p id="rfc.section.9.9.p.1">The "Content-Type" header field indicates the media type of the representation. In the case of responses to the HEAD method,
     2911         the media type is that which would have been sent had the request been a GET.
     2912      </p>
     2913      <div id="rfc.figure.u.44"></div><pre class="inline"><span id="rfc.iref.g.47"></span>  <a href="#header.content-type" class="smpl">Content-Type</a> = <a href="#media.types" class="smpl">media-type</a>
     2914</pre><p id="rfc.section.9.9.p.3">Media types are defined in <a href="#media.types" title="Media Types">Section&nbsp;5.5</a>. An example of the field is
     2915      </p>
     2916      <div id="rfc.figure.u.45"></div><pre class="text">  Content-Type: text/html; charset=ISO-8859-4
     2917</pre><p id="rfc.section.9.9.p.5">Further discussion of Content-Type is provided in <a href="#representation.data" title="Representation Data">Section&nbsp;7.3</a>.
     2918      </p>
    26082919      <div id="rfc.iref.d.3"></div>
    2609       <div id="rfc.iref.h.3"></div>
    2610       <h2 id="rfc.section.9.2"><a href="#rfc.section.9.2">9.2</a>&nbsp;<a id="header.date" href="#header.date">Date</a></h2>
    2611       <p id="rfc.section.9.2.p.1">The "Date" header field represents the date and time at which the message was originated, having the same semantics as the
     2920      <div id="rfc.iref.h.11"></div>
     2921      <h2 id="rfc.section.9.10"><a href="#rfc.section.9.10">9.10</a>&nbsp;<a id="header.date" href="#header.date">Date</a></h2>
     2922      <p id="rfc.section.9.10.p.1">The "Date" header field represents the date and time at which the message was originated, having the same semantics as the
    26122923         Origination Date Field (orig-date) defined in <a href="http://tools.ietf.org/html/rfc5322#section-3.6.1">Section 3.6.1</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.2"><cite title="Internet Message Format">[RFC5322]</cite></a>. The field value is an HTTP-date, as defined in <a href="#http.date" title="Date/Time Formats">Section&nbsp;5.1</a>; it <em class="bcp14">MUST</em> be sent in rfc1123-date format.
    26132924      </p>
    2614       <div id="rfc.figure.u.27"></div><pre class="inline"><span id="rfc.iref.g.35"></span>  <a href="#header.date" class="smpl">Date</a> = <a href="#http.date" class="smpl">HTTP-date</a>
    2615 </pre><p id="rfc.section.9.2.p.3">An example is</p>
    2616       <div id="rfc.figure.u.28"></div><pre class="text">  Date: Tue, 15 Nov 1994 08:12:31 GMT
    2617 </pre><p id="rfc.section.9.2.p.5">Origin servers <em class="bcp14">MUST</em> include a Date header field in all responses, except in these cases:
     2925      <div id="rfc.figure.u.46"></div><pre class="inline"><span id="rfc.iref.g.48"></span>  <a href="#header.date" class="smpl">Date</a> = <a href="#http.date" class="smpl">HTTP-date</a>
     2926</pre><p id="rfc.section.9.10.p.3">An example is</p>
     2927      <div id="rfc.figure.u.47"></div><pre class="text">  Date: Tue, 15 Nov 1994 08:12:31 GMT
     2928</pre><p id="rfc.section.9.10.p.5">Origin servers <em class="bcp14">MUST</em> include a Date header field in all responses, except in these cases:
    26182929      </p>
    26192930      <ol>
    … …  
    26262937         </li>
    26272938      </ol>
    2628       <p id="rfc.section.9.2.p.6">A received message that does not have a Date header field <em class="bcp14">MUST</em> be assigned one by the recipient if the message will be cached by that recipient.
    2629       </p>
    2630       <p id="rfc.section.9.2.p.7">Clients can use the Date header field as well; in order to keep request messages small, they are advised not to include it
     2939      <p id="rfc.section.9.10.p.6">A received message that does not have a Date header field <em class="bcp14">MUST</em> be assigned one by the recipient if the message will be cached by that recipient.
     2940      </p>
     2941      <p id="rfc.section.9.10.p.7">Clients can use the Date header field as well; in order to keep request messages small, they are advised not to include it
    26312942         when it doesn't convey any useful information (as is usually the case for requests that do not contain a payload).
    26322943      </p>
    2633       <p id="rfc.section.9.2.p.8">The HTTP-date sent in a Date header field <em class="bcp14">SHOULD NOT</em> represent a date and time subsequent to the generation of the message. It <em class="bcp14">SHOULD</em> represent the best available approximation of the date and time of message generation, unless the implementation has no means
     2944      <p id="rfc.section.9.10.p.8">The HTTP-date sent in a Date header field <em class="bcp14">SHOULD NOT</em> represent a date and time subsequent to the generation of the message. It <em class="bcp14">SHOULD</em> represent the best available approximation of the date and time of message generation, unless the implementation has no means
    26342945         of generating a reasonably accurate date and time. In theory, the date ought to represent the moment just before the payload
    26352946         is generated. In practice, the date can be generated at any time during the message origination without affecting its semantic
    … …  
    26372948      </p>
    26382949      <div id="rfc.iref.e.1"></div>
    2639       <div id="rfc.iref.h.4"></div>
    2640       <h2 id="rfc.section.9.3"><a href="#rfc.section.9.3">9.3</a>&nbsp;<a id="header.expect" href="#header.expect">Expect</a></h2>
    2641       <p id="rfc.section.9.3.p.1">The "Expect" header field is used to indicate that particular server behaviors are required by the client.</p>
    2642       <div id="rfc.figure.u.29"></div><pre class="inline"><span id="rfc.iref.g.36"></span><span id="rfc.iref.g.37"></span><span id="rfc.iref.g.38"></span><span id="rfc.iref.g.39"></span><span id="rfc.iref.g.40"></span>  <a href="#header.expect" class="smpl">Expect</a>       = 1#<a href="#header.expect" class="smpl">expectation</a>
     2950      <div id="rfc.iref.h.12"></div>
     2951      <h2 id="rfc.section.9.11"><a href="#rfc.section.9.11">9.11</a>&nbsp;<a id="header.expect" href="#header.expect">Expect</a></h2>
     2952      <p id="rfc.section.9.11.p.1">The "Expect" header field is used to indicate that particular server behaviors are required by the client.</p>
     2953      <div id="rfc.figure.u.48"></div><pre class="inline"><span id="rfc.iref.g.49"></span><span id="rfc.iref.g.50"></span><span id="rfc.iref.g.51"></span><span id="rfc.iref.g.52"></span><span id="rfc.iref.g.53"></span>  <a href="#header.expect" class="smpl">Expect</a>       = 1#<a href="#header.expect" class="smpl">expectation</a>
    26432954 
    26442955  <a href="#header.expect" class="smpl">expectation</a>  = <a href="#header.expect" class="smpl">expect-name</a> [ <a href="#core.rules" class="smpl">BWS</a> "=" <a href="#core.rules" class="smpl">BWS</a> <a href="#header.expect" class="smpl">expect-value</a> ]
    … …  
    26482959  <a href="#header.expect" class="smpl">expect-name</a>  = <a href="#core.rules" class="smpl">token</a>
    26492960  <a href="#header.expect" class="smpl">expect-value</a> = <a href="#core.rules" class="smpl">token</a> / <a href="#core.rules" class="smpl">quoted-string</a>
    2650 </pre><p id="rfc.section.9.3.p.3">If all received Expect header field(s) are syntactically valid but contain an expectation that the recipient does not understand
     2961</pre><p id="rfc.section.9.11.p.3">If all received Expect header field(s) are syntactically valid but contain an expectation that the recipient does not understand
    26512962         or cannot comply with, the recipient <em class="bcp14">MUST</em> respond with a 417 (Expectation Failed) status code. A recipient of a syntactically invalid Expectation header field <em class="bcp14">MUST</em> respond with a 4xx status code other than 417.
    26522963      </p>
    2653       <p id="rfc.section.9.3.p.4">The only expectation defined by this specification is:</p>
    2654       <p id="rfc.section.9.3.p.5"><span id="rfc.iref.108"></span><span id="rfc.iref.e.2"></span> 100-continue
     2964      <p id="rfc.section.9.11.p.4">The only expectation defined by this specification is:</p>
     2965      <p id="rfc.section.9.11.p.5"><span id="rfc.iref.137"></span><span id="rfc.iref.e.2"></span> 100-continue
    26552966      </p>
    26562967      <ul class="empty">
    2657          <li>The "100-continue" expectation is defined <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 6.4.3</a> of <a href="#Part1" id="rfc.xref.Part1.47"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. It does not support any expect-params.
    2658          </li>
    2659       </ul>
    2660       <p id="rfc.section.9.3.p.6">Comparison is case-insensitive for names (expect-name), and case-sensitive for values (expect-value).</p>
    2661       <p id="rfc.section.9.3.p.7">The Expect mechanism is hop-by-hop: the above requirements apply to any server, including proxies. However, the Expect header
     2968         <li>The "100-continue" expectation is defined <a href="p1-messaging.html#use.of.the.100.status" title="Use of the 100 (Continue) Status">Section 6.4.3</a> of <a href="#Part1" id="rfc.xref.Part1.48"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. It does not support any expect-params.
     2969         </li>
     2970      </ul>
     2971      <p id="rfc.section.9.11.p.6">Comparison is case-insensitive for names (expect-name), and case-sensitive for values (expect-value).</p>
     2972      <p id="rfc.section.9.11.p.7">The Expect mechanism is hop-by-hop: the above requirements apply to any server, including proxies. However, the Expect header
    26622973         field itself is end-to-end; it <em class="bcp14">MUST</em> be forwarded if the request is forwarded.
    26632974      </p>
    2664       <p id="rfc.section.9.3.p.8">Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header field.</p>
     2975      <p id="rfc.section.9.11.p.8">Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Expect header field.</p>
    26652976      <div id="rfc.iref.f.1"></div>
    2666       <div id="rfc.iref.h.5"></div>
    2667       <h2 id="rfc.section.9.4"><a href="#rfc.section.9.4">9.4</a>&nbsp;<a id="header.from" href="#header.from">From</a></h2>
    2668       <p id="rfc.section.9.4.p.1">The "From" header field, if given, <em class="bcp14">SHOULD</em> contain an Internet e-mail address for the human user who controls the requesting user agent. The address <em class="bcp14">SHOULD</em> be machine-usable, as defined by "mailbox" in <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.3"><cite title="Internet Message Format">[RFC5322]</cite></a>:
    2669       </p>
    2670       <div id="rfc.figure.u.30"></div><pre class="inline"><span id="rfc.iref.g.41"></span>  <a href="#header.from" class="smpl">From</a>    = <a href="#header.from" class="smpl">mailbox</a>
     2977      <div id="rfc.iref.h.13"></div>
     2978      <h2 id="rfc.section.9.12"><a href="#rfc.section.9.12">9.12</a>&nbsp;<a id="header.from" href="#header.from">From</a></h2>
     2979      <p id="rfc.section.9.12.p.1">The "From" header field, if given, <em class="bcp14">SHOULD</em> contain an Internet e-mail address for the human user who controls the requesting user agent. The address <em class="bcp14">SHOULD</em> be machine-usable, as defined by "mailbox" in <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a> of <a href="#RFC5322" id="rfc.xref.RFC5322.3"><cite title="Internet Message Format">[RFC5322]</cite></a>:
     2980      </p>
     2981      <div id="rfc.figure.u.49"></div><pre class="inline"><span id="rfc.iref.g.54"></span>  <a href="#header.from" class="smpl">From</a>    = <a href="#header.from" class="smpl">mailbox</a>
    26712982 
    26722983  <a href="#header.from" class="smpl">mailbox</a> = &lt;mailbox, defined in <a href="#RFC5322" id="rfc.xref.RFC5322.4"><cite title="Internet Message Format">[RFC5322]</cite></a>, <a href="http://tools.ietf.org/html/rfc5322#section-3.4">Section 3.4</a>&gt;
    2673 </pre><p id="rfc.section.9.4.p.3">An example is:</p>
    2674       <div id="rfc.figure.u.31"></div><pre class="text">  From: webmaster@example.org
    2675 </pre><p id="rfc.section.9.4.p.5">This header field <em class="bcp14">MAY</em> be used for logging purposes and as a means for identifying the source of invalid or unwanted requests. It <em class="bcp14">SHOULD NOT</em> be used as an insecure form of access protection. The interpretation of this field is that the request is being performed
     2984</pre><p id="rfc.section.9.12.p.3">An example is:</p>
     2985      <div id="rfc.figure.u.50"></div><pre class="text">  From: webmaster@example.org
     2986</pre><p id="rfc.section.9.12.p.5">This header field <em class="bcp14">MAY</em> be used for logging purposes and as a means for identifying the source of invalid or unwanted requests. It <em class="bcp14">SHOULD NOT</em> be used as an insecure form of access protection. The interpretation of this field is that the request is being performed
    26762987         on behalf of the person given, who accepts responsibility for the method performed. In particular, robot agents <em class="bcp14">SHOULD</em> include this header field so that the person responsible for running the robot can be contacted if problems occur on the receiving
    26772988         end.
    26782989      </p>
    2679       <p id="rfc.section.9.4.p.6">The Internet e-mail address in this field <em class="bcp14">MAY</em> be separate from the Internet host which issued the request. For example, when a request is passed through a proxy the original
     2990      <p id="rfc.section.9.12.p.6">The Internet e-mail address in this field <em class="bcp14">MAY</em> be separate from the Internet host which issued the request. For example, when a request is passed through a proxy the original
    26802991         issuer's address <em class="bcp14">SHOULD</em> be used.
    26812992      </p>
    2682       <p id="rfc.section.9.4.p.7">The client <em class="bcp14">SHOULD NOT</em> send the From header field without the user's approval, as it might conflict with the user's privacy interests or their site's
     2993      <p id="rfc.section.9.12.p.7">The client <em class="bcp14">SHOULD NOT</em> send the From header field without the user's approval, as it might conflict with the user's privacy interests or their site's
    26832994         security policy. It is strongly recommended that the user be able to disable, enable, and modify the value of this field at
    26842995         any time prior to a request.
    26852996      </p>
    26862997      <div id="rfc.iref.l.1"></div>
    2687       <div id="rfc.iref.h.6"></div>
    2688       <h2 id="rfc.section.9.5"><a href="#rfc.section.9.5">9.5</a>&nbsp;<a id="header.location" href="#header.location">Location</a></h2>
    2689       <p id="rfc.section.9.5.p.1">The "Location" header field <em class="bcp14">MAY</em> be sent in responses to refer to a specific resource in accordance with the semantics of the status code.
    2690       </p>
    2691       <div id="rfc.figure.u.32"></div><pre class="inline"><span id="rfc.iref.g.42"></span>  <a href="#header.location" class="smpl">Location</a> = <a href="#abnf.dependencies" class="smpl">URI-reference</a>
    2692 </pre><p id="rfc.section.9.5.p.3">For 201 (Created) responses, the Location is the URI of the new resource which was created by the request. For 3xx responses,
     2998      <div id="rfc.iref.h.14"></div>
     2999      <h2 id="rfc.section.9.13"><a href="#rfc.section.9.13">9.13</a>&nbsp;<a id="header.location" href="#header.location">Location</a></h2>
     3000      <p id="rfc.section.9.13.p.1">The "Location" header field <em class="bcp14">MAY</em> be sent in responses to refer to a specific resource in accordance with the semantics of the status code.
     3001      </p>
     3002      <div id="rfc.figure.u.51"></div><pre class="inline"><span id="rfc.iref.g.55"></span>  <a href="#header.location" class="smpl">Location</a> = <a href="#abnf.dependencies" class="smpl">URI-reference</a>
     3003</pre><p id="rfc.section.9.13.p.3">For 201 (Created) responses, the Location is the URI of the new resource which was created by the request. For 3xx responses,
    26933004         the location <em class="bcp14">SHOULD</em> indicate the server's preferred URI for automatic redirection to the resource.
    26943005      </p>
    2695       <p id="rfc.section.9.5.p.4">The field value consists of a single URI-reference. When it has the form of a relative reference (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-4.2">Section 4.2</a>), the final value is computed by resolving it against the effective request URI (<a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-5">Section 5</a>). If the original URI, as navigated to by the user agent, did contain a fragment identifier, and the final value does not,
     3006      <p id="rfc.section.9.13.p.4">The field value consists of a single URI-reference. When it has the form of a relative reference (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-4.2">Section 4.2</a>), the final value is computed by resolving it against the effective request URI (<a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-5">Section 5</a>). If the original URI, as navigated to by the user agent, did contain a fragment identifier, and the final value does not,
    26963007         then the original URI's fragment identifier is added to the final value.
    26973008      </p>
    2698       <div id="rfc.figure.u.33"></div>
     3009      <div id="rfc.figure.u.52"></div>
    26993010      <p>For example, the original URI "http://www.example.org/~tim", combined with a field value given as:</p>  <pre class="text">  Location: /pub/WWW/People.html#tim
    27003011</pre>  <p>would result in a final value of "http://www.example.org/pub/WWW/People.html#tim"</p>
    2701       <div id="rfc.figure.u.34"></div>
     3012      <div id="rfc.figure.u.53"></div>
    27023013      <p>An original URI "http://www.example.org/index.html#larry", combined with a field value given as:</p>  <pre class="text">  Location: http://www.example.net/index.html
    27033014</pre>  <p>would result in a final value of "http://www.example.net/index.html#larry", preserving the original fragment identifier.</p>
    2704       <div class="note" id="rfc.section.9.5.p.7">
     3015      <div class="note" id="rfc.section.9.13.p.7">
    27053016         <p> <b>Note:</b> Some recipients attempt to recover from Location fields that are not valid URI references. This specification does not mandate
    27063017            or define such processing, but does allow it (see <a href="#intro.conformance.and.error.handling" title="Conformance and Error Handling">Section&nbsp;1.2</a>).
    27073018         </p>
    27083019      </div>
    2709       <p id="rfc.section.9.5.p.8">There are circumstances in which a fragment identifier in a Location URI would not be appropriate. For instance, when it appears
     3020      <p id="rfc.section.9.13.p.8">There are circumstances in which a fragment identifier in a Location URI would not be appropriate. For instance, when it appears
    27103021         in a 201 Created response, where the Location header field specifies the URI for the entire created resource.
    27113022      </p>
    2712       <div class="note" id="rfc.section.9.5.p.9">
    2713          <p> <b>Note:</b> The Content-Location header field (<a href="#header.content-location" id="rfc.xref.header.content-location.3" title="Content-Location">Section&nbsp;9.17</a>) differs from Location in that the Content-Location identifies the most specific resource corresponding to the enclosed representation.
     3023      <div class="note" id="rfc.section.9.13.p.9">
     3024         <p> <b>Note:</b> The Content-Location header field (<a href="#header.content-location" id="rfc.xref.header.content-location.3" title="Content-Location">Section&nbsp;9.8</a>) differs from Location in that the Content-Location identifies the most specific resource corresponding to the enclosed representation.
    27143025            It is therefore possible for a response to contain header fields for both Location and Content-Location.
    27153026         </p>
    27163027      </div>
    27173028      <div id="rfc.iref.m.9"></div>
    2718       <div id="rfc.iref.h.7"></div>
    2719       <h2 id="rfc.section.9.6"><a href="#rfc.section.9.6">9.6</a>&nbsp;<a id="header.max-forwards" href="#header.max-forwards">Max-Forwards</a></h2>
    2720       <p id="rfc.section.9.6.p.1">The "Max-Forwards" header field provides a mechanism with the TRACE (<a href="#TRACE" id="rfc.xref.TRACE.1" title="TRACE">Section&nbsp;2.3.7</a>) and OPTIONS (<a href="#OPTIONS" id="rfc.xref.OPTIONS.1" title="OPTIONS">Section&nbsp;2.3.1</a>) methods to limit the number of times that the request is forwarded by proxies. This can be useful when the client is attempting
     3029      <div id="rfc.iref.h.15"></div>
     3030      <h2 id="rfc.section.9.14"><a href="#rfc.section.9.14">9.14</a>&nbsp;<a id="header.max-forwards" href="#header.max-forwards">Max-Forwards</a></h2>
     3031      <p id="rfc.section.9.14.p.1">The "Max-Forwards" header field provides a mechanism with the TRACE (<a href="#TRACE" id="rfc.xref.TRACE.1" title="TRACE">Section&nbsp;2.3.7</a>) and OPTIONS (<a href="#OPTIONS" id="rfc.xref.OPTIONS.1" title="OPTIONS">Section&nbsp;2.3.1</a>) methods to limit the number of times that the request is forwarded by proxies. This can be useful when the client is attempting
    27213032         to trace a request which appears to be failing or looping mid-chain.
    27223033      </p>
    2723       <div id="rfc.figure.u.35"></div><pre class="inline"><span id="rfc.iref.g.43"></span>  <a href="#header.max-forwards" class="smpl">Max-Forwards</a> = 1*<a href="#notation" class="smpl">DIGIT</a>
    2724 </pre><p id="rfc.section.9.6.p.3">The Max-Forwards value is a decimal integer indicating the remaining number of times this request message can be forwarded.</p>
    2725       <p id="rfc.section.9.6.p.4">Each recipient of a TRACE or OPTIONS request containing a Max-Forwards header field <em class="bcp14">MUST</em> check and update its value prior to forwarding the request. If the received value is zero (0), the recipient <em class="bcp14">MUST NOT</em> forward the request; instead, it <em class="bcp14">MUST</em> respond as the final recipient. If the received Max-Forwards value is greater than zero, then the forwarded message <em class="bcp14">MUST</em> contain an updated Max-Forwards field with a value decremented by one (1).
    2726       </p>
    2727       <p id="rfc.section.9.6.p.5">The Max-Forwards header field <em class="bcp14">MAY</em> be ignored for all other request methods.
     3034      <div id="rfc.figure.u.54"></div><pre class="inline"><span id="rfc.iref.g.56"></span>  <a href="#header.max-forwards" class="smpl">Max-Forwards</a> = 1*<a href="#notation" class="smpl">DIGIT</a>
     3035</pre><p id="rfc.section.9.14.p.3">The Max-Forwards value is a decimal integer indicating the remaining number of times this request message can be forwarded.</p>
     3036      <p id="rfc.section.9.14.p.4">Each recipient of a TRACE or OPTIONS request containing a Max-Forwards header field <em class="bcp14">MUST</em> check and update its value prior to forwarding the request. If the received value is zero (0), the recipient <em class="bcp14">MUST NOT</em> forward the request; instead, it <em class="bcp14">MUST</em> respond as the final recipient. If the received Max-Forwards value is greater than zero, then the forwarded message <em class="bcp14">MUST</em> contain an updated Max-Forwards field with a value decremented by one (1).
     3037      </p>
     3038      <p id="rfc.section.9.14.p.5">The Max-Forwards header field <em class="bcp14">MAY</em> be ignored for all other request methods.
    27283039      </p>
    27293040      <div id="rfc.iref.r.2"></div>
    2730       <div id="rfc.iref.h.8"></div>
    2731       <h2 id="rfc.section.9.7"><a href="#rfc.section.9.7">9.7</a>&nbsp;<a id="header.referer" href="#header.referer">Referer</a></h2>
    2732       <p id="rfc.section.9.7.p.1">The "Referer" [sic] header field allows the client to specify the URI of the resource from which the target URI was obtained
     3041      <div id="rfc.iref.h.16"></div>
     3042      <h2 id="rfc.section.9.15"><a href="#rfc.section.9.15">9.15</a>&nbsp;<a id="header.referer" href="#header.referer">Referer</a></h2>
     3043      <p id="rfc.section.9.15.p.1">The "Referer" [sic] header field allows the client to specify the URI of the resource from which the target URI was obtained
    27333044         (the "referrer", although the header field is misspelled.).
    27343045      </p>
    2735       <p id="rfc.section.9.7.p.2">The Referer header field allows servers to generate lists of back-links to resources for interest, logging, optimized caching,
     3046      <p id="rfc.section.9.15.p.2">The Referer header field allows servers to generate lists of back-links to resources for interest, logging, optimized caching,
    27363047         etc. It also allows obsolete or mistyped links to be traced for maintenance. Some servers use Referer as a means of controlling
    27373048         where they allow links from (so-called "deep linking"), but legitimate requests do not always contain a Referer header field.
    27383049      </p>
    2739       <p id="rfc.section.9.7.p.3">If the target URI was obtained from a source that does not have its own URI (e.g., input from the user keyboard), the Referer
     3050      <p id="rfc.section.9.15.p.3">If the target URI was obtained from a source that does not have its own URI (e.g., input from the user keyboard), the Referer
    27403051         field <em class="bcp14">MUST</em> either be sent with the value "about:blank", or not be sent at all. Note that this requirement does not apply to sources with
    27413052         non-HTTP URIs (e.g., FTP).
    27423053      </p>
    2743       <div id="rfc.figure.u.36"></div><pre class="inline"><span id="rfc.iref.g.44"></span>  <a href="#header.referer" class="smpl">Referer</a> = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a>
    2744 </pre><p id="rfc.section.9.7.p.5">Example:</p>
    2745       <div id="rfc.figure.u.37"></div><pre class="text">  Referer: http://www.example.org/hypertext/Overview.html
    2746 </pre><p id="rfc.section.9.7.p.7">If the field value is a relative URI, it <em class="bcp14">SHOULD</em> be interpreted relative to the effective request URI. The URI <em class="bcp14">MUST NOT</em> include a fragment. See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;11.2</a> for security considerations.
     3054      <div id="rfc.figure.u.55"></div><pre class="inline"><span id="rfc.iref.g.57"></span>  <a href="#header.referer" class="smpl">Referer</a> = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a>
     3055</pre><p id="rfc.section.9.15.p.5">Example:</p>
     3056      <div id="rfc.figure.u.56"></div><pre class="text">  Referer: http://www.example.org/hypertext/Overview.html
     3057</pre><p id="rfc.section.9.15.p.7">If the field value is a relative URI, it <em class="bcp14">SHOULD</em> be interpreted relative to the effective request URI. The URI <em class="bcp14">MUST NOT</em> include a fragment. See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;11.2</a> for security considerations.
    27473058      </p>
    27483059      <div id="rfc.iref.r.3"></div>
    2749       <div id="rfc.iref.h.9"></div>
    2750       <h2 id="rfc.section.9.8"><a href="#rfc.section.9.8">9.8</a>&nbsp;<a id="header.retry-after" href="#header.retry-after">Retry-After</a></h2>
    2751       <p id="rfc.section.9.8.p.1">The header "Retry-After" field can be used with a 503 (Service Unavailable) response to indicate how long the service is expected
     3060      <div id="rfc.iref.h.17"></div>
     3061      <h2 id="rfc.section.9.16"><a href="#rfc.section.9.16">9.16</a>&nbsp;<a id="header.retry-after" href="#header.retry-after">Retry-After</a></h2>
     3062      <p id="rfc.section.9.16.p.1">The header "Retry-After" field can be used with a 503 (Service Unavailable) response to indicate how long the service is expected
    27523063         to be unavailable to the requesting client. This field <em class="bcp14">MAY</em> also be used with any 3xx (Redirection) response to indicate the minimum time the user-agent is asked to wait before issuing
    27533064         the redirected request.
    27543065      </p>
    2755       <p id="rfc.section.9.8.p.2">The value of this field can be either an HTTP-date or an integer number of seconds (in decimal) after the time of the response.</p>
    2756       <div id="rfc.figure.u.38"></div><pre class="inline"><span id="rfc.iref.g.45"></span>  <a href="#header.retry-after" class="smpl">Retry-After</a> = <a href="#http.date" class="smpl">HTTP-date</a> / <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>
     3066      <p id="rfc.section.9.16.p.2">The value of this field can be either an HTTP-date or an integer number of seconds (in decimal) after the time of the response.</p>
     3067      <div id="rfc.figure.u.57"></div><pre class="inline"><span id="rfc.iref.g.58"></span>  <a href="#header.retry-after" class="smpl">Retry-After</a> = <a href="#http.date" class="smpl">HTTP-date</a> / <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>
    27573068</pre><div id="rule.delta-seconds">
    2758          <p id="rfc.section.9.8.p.4">  Time spans are non-negative decimal integers, representing time in seconds.</p>
     3069         <p id="rfc.section.9.16.p.4">  Time spans are non-negative decimal integers, representing time in seconds.</p>
    27593070      </div>
    2760       <div id="rfc.figure.u.39"></div><pre class="inline"><span id="rfc.iref.g.46"></span>  <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>  = 1*<a href="#notation" class="smpl">DIGIT</a>
    2761 </pre><p id="rfc.section.9.8.p.6">Two examples of its use are</p>
    2762       <div id="rfc.figure.u.40"></div><pre class="text">  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
     3071      <div id="rfc.figure.u.58"></div><pre class="inline"><span id="rfc.iref.g.59"></span>  <a href="#rule.delta-seconds" class="smpl">delta-seconds</a>  = 1*<a href="#notation" class="smpl">DIGIT</a>
     3072</pre><p id="rfc.section.9.16.p.6">Two examples of its use are</p>
     3073      <div id="rfc.figure.u.59"></div><pre class="text">  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
    27633074  Retry-After: 120
    2764 </pre><p id="rfc.section.9.8.p.8">In the latter example, the delay is 2 minutes.</p>
     3075</pre><p id="rfc.section.9.16.p.8">In the latter example, the delay is 2 minutes.</p>
    27653076      <div id="rfc.iref.s.39"></div>
    2766       <div id="rfc.iref.h.10"></div>
    2767       <h2 id="rfc.section.9.9"><a href="#rfc.section.9.9">9.9</a>&nbsp;<a id="header.server" href="#header.server">Server</a></h2>
    2768       <p id="rfc.section.9.9.p.1">The "Server" header field contains information about the software used by the origin server to handle the request.</p>
    2769       <p id="rfc.section.9.9.p.2">The field can contain multiple product tokens (<a href="#product.tokens" title="Product Tokens">Section&nbsp;5.2</a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.48"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the server and any significant subproducts. The product tokens are listed in order of their significance for
     3077      <div id="rfc.iref.h.18"></div>
     3078      <h2 id="rfc.section.9.17"><a href="#rfc.section.9.17">9.17</a>&nbsp;<a id="header.server" href="#header.server">Server</a></h2>
     3079      <p id="rfc.section.9.17.p.1">The "Server" header field contains information about the software used by the origin server to handle the request.</p>
     3080      <p id="rfc.section.9.17.p.2">The field can contain multiple product tokens (<a href="#product.tokens" title="Product Tokens">Section&nbsp;5.2</a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.49"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the server and any significant subproducts. The product tokens are listed in order of their significance for
    27703081         identifying the application.
    27713082      </p>
    2772       <div id="rfc.figure.u.41"></div><pre class="inline"><span id="rfc.iref.g.47"></span>  <a href="#header.server" class="smpl">Server</a> = <a href="#product.tokens" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#product.tokens" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) )
    2773 </pre><p id="rfc.section.9.9.p.4">Example:</p>
    2774       <div id="rfc.figure.u.42"></div><pre class="text">  Server: CERN/3.0 libwww/2.17
    2775 </pre><p id="rfc.section.9.9.p.6">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server header field. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 6.2</a> of <a href="#Part1" id="rfc.xref.Part1.49"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
    2776       </p>
    2777       <div class="note" id="rfc.section.9.9.p.7">
     3083      <div id="rfc.figure.u.60"></div><pre class="inline"><span id="rfc.iref.g.60"></span>  <a href="#header.server" class="smpl">Server</a> = <a href="#product.tokens" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#product.tokens" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) )
     3084</pre><p id="rfc.section.9.17.p.4">Example:</p>
     3085      <div id="rfc.figure.u.61"></div><pre class="text">  Server: CERN/3.0 libwww/2.17
     3086</pre><p id="rfc.section.9.17.p.6">If the response is being forwarded through a proxy, the proxy application <em class="bcp14">MUST NOT</em> modify the Server header field. Instead, it <em class="bcp14">MUST</em> include a Via field (as described in <a href="p1-messaging.html#header.via" title="Via">Section 6.2</a> of <a href="#Part1" id="rfc.xref.Part1.50"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>).
     3087      </p>
     3088      <div class="note" id="rfc.section.9.17.p.7">
    27783089         <p> <b>Note:</b> Revealing the specific software version of the server might allow the server machine to become more vulnerable to attacks
    27793090            against software that is known to contain security holes. Server implementors are encouraged to make this field a configurable
    … …  
    27823093      </div>
    27833094      <div id="rfc.iref.u.1"></div>
    2784       <div id="rfc.iref.h.11"></div>
    2785       <h2 id="rfc.section.9.10"><a href="#rfc.section.9.10">9.10</a>&nbsp;<a id="header.user-agent" href="#header.user-agent">User-Agent</a></h2>
    2786       <p id="rfc.section.9.10.p.1">The "User-Agent" header field contains information about the user agent originating the request. User agents <em class="bcp14">SHOULD</em> include this field with requests.
    2787       </p>
    2788       <p id="rfc.section.9.10.p.2">Typically, it is used for statistical purposes, the tracing of protocol violations, and tailoring responses to avoid particular
     3095      <div id="rfc.iref.h.19"></div>
     3096      <h2 id="rfc.section.9.18"><a href="#rfc.section.9.18">9.18</a>&nbsp;<a id="header.user-agent" href="#header.user-agent">User-Agent</a></h2>
     3097      <p id="rfc.section.9.18.p.1">The "User-Agent" header field contains information about the user agent originating the request. User agents <em class="bcp14">SHOULD</em> include this field with requests.
     3098      </p>
     3099      <p id="rfc.section.9.18.p.2">Typically, it is used for statistical purposes, the tracing of protocol violations, and tailoring responses to avoid particular
    27893100         user agent limitations.
    27903101      </p>
    2791       <p id="rfc.section.9.10.p.3">The field can contain multiple product tokens (<a href="#product.tokens" title="Product Tokens">Section&nbsp;5.2</a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.50"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the agent and its significant subproducts. By convention, the product tokens are listed in order of their significance
     3102      <p id="rfc.section.9.18.p.3">The field can contain multiple product tokens (<a href="#product.tokens" title="Product Tokens">Section&nbsp;5.2</a>) and comments (<a href="p1-messaging.html#header.fields" title="Header Fields">Section 3.2</a> of <a href="#Part1" id="rfc.xref.Part1.51"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>) identifying the agent and its significant subproducts. By convention, the product tokens are listed in order of their significance
    27923103         for identifying the application.
    27933104      </p>
    2794       <p id="rfc.section.9.10.p.4">Because this field is usually sent on every request a user agent makes, implementations are encouraged not to include needlessly
     3105      <p id="rfc.section.9.18.p.4">Because this field is usually sent on every request a user agent makes, implementations are encouraged not to include needlessly
    27953106         fine-grained detail, and to limit (or even prohibit) the addition of subproducts by third parties. Overly long and detailed
    27963107         User-Agent field values make requests larger and can also be used to identify ("fingerprint") the user against their wishes.
    27973108      </p>
    2798       <p id="rfc.section.9.10.p.5">Likewise, implementations are encouraged not to use the product tokens of other implementations in order to declare compatibility
     3109      <p id="rfc.section.9.18.p.5">Likewise, implementations are encouraged not to use the product tokens of other implementations in order to declare compatibility
    27993110         with them, as this circumvents the purpose of the field. Finally, they are encouraged not to use comments to identify products;
    28003111         doing so makes the field value more difficult to parse.
    28013112      </p>
    2802       <div id="rfc.figure.u.43"></div><pre class="inline"><span id="rfc.iref.g.48"></span>  <a href="#header.user-agent" class="smpl">User-Agent</a> = <a href="#product.tokens" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#product.tokens" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) )
    2803 </pre><p id="rfc.section.9.10.p.7">Example:</p>
    2804       <div id="rfc.figure.u.44"></div><pre class="text">  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
    2805 </pre><div id="rfc.iref.a.2"></div>
    2806       <div id="rfc.iref.h.12"></div>
    2807       <h2 id="rfc.section.9.11"><a href="#rfc.section.9.11">9.11</a>&nbsp;<a id="header.accept" href="#header.accept">Accept</a></h2>
    2808       <p id="rfc.section.9.11.p.1">The "Accept" header field can be used by user agents to specify response media types that are acceptable. Accept header fields
    2809          can be used to indicate that the request is specifically limited to a small set of desired types, as in the case of a request
    2810          for an in-line image.
    2811       </p>
    2812       <div id="rfc.figure.u.45"></div><pre class="inline"><span id="rfc.iref.g.49"></span><span id="rfc.iref.g.50"></span><span id="rfc.iref.g.51"></span><span id="rfc.iref.g.52"></span>  <a href="#header.accept" class="smpl">Accept</a> = #( <a href="#header.accept" class="smpl">media-range</a> [ <a href="#header.accept" class="smpl">accept-params</a> ] )
    2813  
    2814   <a href="#header.accept" class="smpl">media-range</a>    = ( "*/*"
    2815                    / ( <a href="#media.types" class="smpl">type</a> "/" "*" )
    2816                    / ( <a href="#media.types" class="smpl">type</a> "/" <a href="#media.types" class="smpl">subtype</a> )
    2817                    ) *( <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> <a href="#rule.parameter" class="smpl">parameter</a> )
    2818   <a href="#header.accept" class="smpl">accept-params</a>  = <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> "q=" <a href="#abnf.dependencies" class="smpl">qvalue</a> *( <a href="#header.accept" class="smpl">accept-ext</a> )
    2819   <a href="#header.accept" class="smpl">accept-ext</a>     = <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> <a href="#core.rules" class="smpl">token</a> [ "=" <a href="#core.rules" class="smpl">word</a> ]
    2820 </pre><p id="rfc.section.9.11.p.3">The asterisk "*" character is used to group media types into ranges, with "*/*" indicating all media types and "type/*" indicating
    2821          all subtypes of that type. The media-range <em class="bcp14">MAY</em> include media type parameters that are applicable to that range.
    2822       </p>
    2823       <p id="rfc.section.9.11.p.4">Each media-range <em class="bcp14">MAY</em> be followed by one or more accept-params, beginning with the "q" parameter for indicating a relative quality factor. The first
    2824          "q" parameter (if any) separates the media-range parameter(s) from the accept-params. Quality factors allow the user or user
    2825          agent to indicate the relative degree of preference for that media-range, using the qvalue scale from 0 to 1 (qvalue;). The
    2826          default value is q=1.
    2827       </p>
    2828       <div class="note" id="rfc.section.9.11.p.5">
    2829          <p> <b>Note:</b> Use of the "q" parameter name to separate media type parameters from Accept extension parameters is due to historical practice.
    2830             Although this prevents any media type parameter named "q" from being used with a media range, such an event is believed to
    2831             be unlikely given the lack of any "q" parameters in the IANA media type registry and the rare usage of any media type parameters
    2832             in Accept. Future media types are discouraged from registering any parameter named "q".
    2833          </p>
    2834       </div>
    2835       <p id="rfc.section.9.11.p.6">The example</p>
    2836       <div id="rfc.figure.u.46"></div><pre class="text">  Accept: audio/*; q=0.2, audio/basic
    2837 </pre><p id="rfc.section.9.11.p.8"> <em class="bcp14">SHOULD</em> be interpreted as "I prefer audio/basic, but send me any audio type if it is the best available after an 80% mark-down in
    2838          quality".
    2839       </p>
    2840       <p id="rfc.section.9.11.p.9">A request without any Accept header field implies that the user agent will accept any media type in response. If an Accept
    2841          header field is present in a request and none of the available representations for the response have a media type that is
    2842          listed as acceptable, the origin server <em class="bcp14">MAY</em> either honor the Accept header field by sending a 406 (Not Acceptable) response or disregard the Accept header field by treating
    2843          the response as if it is not subject to content negotiation.
    2844       </p>
    2845       <p id="rfc.section.9.11.p.10">A more elaborate example is</p>
    2846       <div id="rfc.figure.u.47"></div><pre class="text">  Accept: text/plain; q=0.5, text/html,
    2847           text/x-dvi; q=0.8, text/x-c
    2848 </pre><p id="rfc.section.9.11.p.12">Verbally, this would be interpreted as "text/html and text/x-c are the preferred media types, but if they do not exist, then
    2849          send the text/x-dvi representation, and if that does not exist, send the text/plain representation".
    2850       </p>
    2851       <p id="rfc.section.9.11.p.13">Media ranges can be overridden by more specific media ranges or specific media types. If more than one media range applies
    2852          to a given type, the most specific reference has precedence. For example,
    2853       </p>
    2854       <div id="rfc.figure.u.48"></div><pre class="text">  Accept: text/*, text/plain, text/plain;format=flowed, */*
    2855 </pre><p id="rfc.section.9.11.p.15">have the following precedence: </p>
    2856       <ol>
    2857          <li>text/plain;format=flowed</li>
    2858          <li>text/plain</li>
    2859          <li>text/*</li>
    2860          <li>*/*</li>
    2861       </ol>
    2862       <p id="rfc.section.9.11.p.16">The media type quality factor associated with a given type is determined by finding the media range with the highest precedence
    2863          which matches that type. For example,
    2864       </p>
    2865       <div id="rfc.figure.u.49"></div><pre class="text">  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
    2866           text/html;level=2;q=0.4, */*;q=0.5
    2867 </pre><p id="rfc.section.9.11.p.18">would cause the following values to be associated:</p>
    2868       <div id="rfc.table.u.7">
    2869          <table class="tt full left" cellpadding="3" cellspacing="0">
    2870             <thead>
    2871                <tr>
    2872                   <th>Media Type</th>
    2873                   <th>Quality Value</th>
    2874                </tr>
    2875             </thead>
    2876             <tbody>
    2877                <tr>
    2878                   <td class="left">text/html;level=1</td>
    2879                   <td class="left">1</td>
    2880                </tr>
    2881                <tr>
    2882                   <td class="left">text/html</td>
    2883                   <td class="left">0.7</td>
    2884                </tr>
    2885                <tr>
    2886                   <td class="left">text/plain</td>
    2887                   <td class="left">0.3</td>
    2888                </tr>
    2889                <tr>
    2890                   <td class="left">image/jpeg</td>
    2891                   <td class="left">0.5</td>
    2892                </tr>
    2893                <tr>
    2894                   <td class="left">text/html;level=2</td>
    2895                   <td class="left">0.4</td>
    2896                </tr>
    2897                <tr>
    2898                   <td class="left">text/html;level=3</td>
    2899                   <td class="left">0.7</td>
    2900                </tr>
    2901             </tbody>
    2902          </table>
    2903       </div>
    2904       <p id="rfc.section.9.11.p.19"> <b>Note:</b> A user agent might be provided with a default set of quality values for certain media ranges. However, unless the user agent
    2905          is a closed system which cannot interact with other rendering agents, this default set ought to be configurable by the user.
    2906       </p>
    2907       <div id="rfc.iref.a.3"></div>
    2908       <div id="rfc.iref.h.13"></div>
    2909       <h2 id="rfc.section.9.12"><a href="#rfc.section.9.12">9.12</a>&nbsp;<a id="header.accept-charset" href="#header.accept-charset">Accept-Charset</a></h2>
    2910       <p id="rfc.section.9.12.p.1">The "Accept-Charset" header field can be used by user agents to indicate what character encodings are acceptable in a response
    2911          payload. This field allows clients capable of understanding more comprehensive or special-purpose character encodings to signal
    2912          that capability to a server which is capable of representing documents in those character encodings.
    2913       </p>
    2914       <div id="rfc.figure.u.50"></div><pre class="inline"><span id="rfc.iref.g.53"></span>  <a href="#header.accept-charset" class="smpl">Accept-Charset</a> = 1#( ( <a href="#rule.charset" class="smpl">charset</a> / "*" )
    2915                          [ <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> "q=" <a href="#abnf.dependencies" class="smpl">qvalue</a> ] )
    2916 </pre><p id="rfc.section.9.12.p.3">Character encoding values (a.k.a., charsets) are described in <a href="#character.sets" title="Character Encodings (charset)">Section&nbsp;5.3</a>. Each charset <em class="bcp14">MAY</em> be given an associated quality value which represents the user's preference for that charset. The default value is q=1. An
    2917          example is
    2918       </p>
    2919       <div id="rfc.figure.u.51"></div><pre class="text">  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
    2920 </pre><p id="rfc.section.9.12.p.5">The special value "*", if present in the Accept-Charset field, matches every character encoding which is not mentioned elsewhere
    2921          in the Accept-Charset field. If no "*" is present in an Accept-Charset field, then all character encodings not explicitly
    2922          mentioned get a quality value of 0.
    2923       </p>
    2924       <p id="rfc.section.9.12.p.6">A request without any Accept-Charset header field implies that the user agent will accept any character encoding in response.
    2925          If an Accept-Charset header field is present in a request and none of the available representations for the response have
    2926          a character encoding that is listed as acceptable, the origin server <em class="bcp14">MAY</em> either honor the Accept-Charset header field by sending a 406 (Not Acceptable) response or disregard the Accept-Charset header
    2927          field by treating the response as if it is not subject to content negotiation.
    2928       </p>
    2929       <div id="rfc.iref.a.4"></div>
    2930       <div id="rfc.iref.h.14"></div>
    2931       <h2 id="rfc.section.9.13"><a href="#rfc.section.9.13">9.13</a>&nbsp;<a id="header.accept-encoding" href="#header.accept-encoding">Accept-Encoding</a></h2>
    2932       <p id="rfc.section.9.13.p.1">The "Accept-Encoding" header field can be used by user agents to indicate what response content-codings (<a href="#content.codings" title="Content Codings">Section&nbsp;5.4</a>) are acceptable in the response. An "identity" token is used as a synonym for "no encoding" in order to communicate when
    2933          no encoding is preferred.
    2934       </p>
    2935       <div id="rfc.figure.u.52"></div><pre class="inline"><span id="rfc.iref.g.54"></span><span id="rfc.iref.g.55"></span>  <a href="#header.accept-encoding" class="smpl">Accept-Encoding</a>  = #( <a href="#header.accept-encoding" class="smpl">codings</a> [ <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> "q=" <a href="#abnf.dependencies" class="smpl">qvalue</a> ] )
    2936   <a href="#header.accept-encoding" class="smpl">codings</a>          = <a href="#content.codings" class="smpl">content-coding</a> / "identity" / "*"
    2937 </pre><p id="rfc.section.9.13.p.3">Each codings value <em class="bcp14">MAY</em> be given an associated quality value which represents the preference for that encoding. The default value is q=1.
    2938       </p>
    2939       <p id="rfc.section.9.13.p.4">For example,</p>
    2940       <div id="rfc.figure.u.53"></div><pre class="text">  Accept-Encoding: compress, gzip
    2941   Accept-Encoding:
    2942   Accept-Encoding: *
    2943   Accept-Encoding: compress;q=0.5, gzip;q=1.0
    2944   Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
    2945 </pre><p id="rfc.section.9.13.p.6">A server tests whether a content-coding for a given representation is acceptable, according to an Accept-Encoding field, using
    2946          these rules:
    2947       </p>
    2948       <ol>
    2949          <li>The special "*" symbol in an Accept-Encoding field matches any available content-coding not explicitly listed in the header
    2950             field.
    2951          </li>
    2952          <li>If the representation has no content-coding, then it is acceptable by default unless specifically excluded by the Accept-Encoding
    2953             field stating either "identity;q=0" or "*;q=0" without a more specific entry for "identity".
    2954          </li>
    2955          <li>If the representation's content-coding is one of the content-codings listed in the Accept-Encoding field, then it is acceptable
    2956             unless it is accompanied by a qvalue of 0. (As defined in qvalue;, a qvalue of 0 means "not acceptable".)
    2957          </li>
    2958          <li>If multiple content-codings are acceptable, then the acceptable content-coding with the highest non-zero qvalue is preferred.</li>
    2959       </ol>
    2960       <p id="rfc.section.9.13.p.7">An Accept-Encoding header field with a combined field-value that is empty implies that the user agent does not want any content-coding
    2961          in response. If an Accept-Encoding header field is present in a request and none of the available representations for the
    2962          response have a content-coding that is listed as acceptable, the origin server <em class="bcp14">SHOULD</em> send a response without any content-coding.
    2963       </p>
    2964       <p id="rfc.section.9.13.p.8">A request without an Accept-Encoding header field implies that the user agent will accept any content-coding in response,
    2965          but a representation without content-coding is preferred for compatibility with the widest variety of user agents.
    2966       </p>
    2967       <div class="note" id="rfc.section.9.13.p.9">
    2968          <p> <b>Note:</b> Most HTTP/1.0 applications do not recognize or obey qvalues associated with content-codings. This means that qvalues will
    2969             not work and are not permitted with x-gzip or x-compress.
    2970          </p>
    2971       </div>
    2972       <div id="rfc.iref.a.5"></div>
    2973       <div id="rfc.iref.h.15"></div>
    2974       <h2 id="rfc.section.9.14"><a href="#rfc.section.9.14">9.14</a>&nbsp;<a id="header.accept-language" href="#header.accept-language">Accept-Language</a></h2>
    2975       <p id="rfc.section.9.14.p.1">The "Accept-Language" header field can be used by user agents to indicate the set of natural languages that are preferred
    2976          in the response. Language tags are defined in <a href="#language.tags" title="Language Tags">Section&nbsp;5.6</a>.
    2977       </p>
    2978       <div id="rfc.figure.u.54"></div><pre class="inline"><span id="rfc.iref.g.56"></span><span id="rfc.iref.g.57"></span>  <a href="#header.accept-language" class="smpl">Accept-Language</a> =
    2979                     1#( <a href="#header.accept-language" class="smpl">language-range</a> [ <a href="#core.rules" class="smpl">OWS</a> ";" <a href="#core.rules" class="smpl">OWS</a> "q=" <a href="#abnf.dependencies" class="smpl">qvalue</a> ] )
    2980   <a href="#header.accept-language" class="smpl">language-range</a>  =
    2981             &lt;language-range, defined in <a href="#RFC4647" id="rfc.xref.RFC4647.1"><cite title="Matching of Language Tags">[RFC4647]</cite></a>, <a href="http://tools.ietf.org/html/rfc4647#section-2.1">Section 2.1</a>&gt;
    2982 </pre><p id="rfc.section.9.14.p.3">Each language-range can be given an associated quality value which represents an estimate of the user's preference for the
    2983          languages specified by that range. The quality value defaults to "q=1". For example,
    2984       </p>
    2985       <div id="rfc.figure.u.55"></div><pre class="text">  Accept-Language: da, en-gb;q=0.8, en;q=0.7
    2986 </pre><p id="rfc.section.9.14.p.5">would mean: "I prefer Danish, but will accept British English and other types of English". (see also <a href="http://tools.ietf.org/html/rfc4647#section-2.3">Section 2.3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.2"><cite title="Matching of Language Tags">[RFC4647]</cite></a>)
    2987       </p>
    2988       <p id="rfc.section.9.14.p.6">For matching, <a href="http://tools.ietf.org/html/rfc4647#section-3">Section 3</a> of <a href="#RFC4647" id="rfc.xref.RFC4647.3"><cite title="Matching of Language Tags">[RFC4647]</cite></a> defines several matching schemes. Implementations can offer the most appropriate matching scheme for their requirements.
    2989       </p>
    2990       <div class="note" id="rfc.section.9.14.p.7">
    2991          <p> <b>Note:</b> The "Basic Filtering" scheme (<a href="#RFC4647" id="rfc.xref.RFC4647.4"><cite title="Matching of Language Tags">[RFC4647]</cite></a>, <a href="http://tools.ietf.org/html/rfc4647#section-3.3.1">Section 3.3.1</a>) is identical to the matching scheme that was previously defined in <a href="http://tools.ietf.org/html/rfc2616#section-14.4">Section 14.4</a> of <a href="#RFC2616" id="rfc.xref.RFC2616.3"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>.
    2992          </p>
    2993       </div>
    2994       <p id="rfc.section.9.14.p.8">It might be contrary to the privacy expectations of the user to send an Accept-Language header field with the complete linguistic
    2995          preferences of the user in every request. For a discussion of this issue, see <a href="#privacy.issues.connected.to.accept.header.fields" title="Privacy Issues Connected to Accept Header Fields">Section&nbsp;11.5</a>.
    2996       </p>
    2997       <p id="rfc.section.9.14.p.9">As intelligibility is highly dependent on the individual user, it is recommended that client applications make the choice
    2998          of linguistic preference available to the user. If the choice is not made available, then the Accept-Language header field <em class="bcp14">MUST NOT</em> be given in the request.
    2999       </p>
    3000       <div class="note" id="rfc.section.9.14.p.10">
    3001          <p> <b>Note:</b> When making the choice of linguistic preference available to the user, we remind implementors of the fact that users are not
    3002             familiar with the details of language matching as described above, and ought to be provided appropriate guidance. As an example,
    3003             users might assume that on selecting "en-gb", they will be served any kind of English document if British English is not available.
    3004             A user agent might suggest in such a case to add "en" to get the best matching behavior.
    3005          </p>
    3006       </div>
    3007       <div id="rfc.iref.c.7"></div>
    3008       <div id="rfc.iref.h.16"></div>
    3009       <h2 id="rfc.section.9.15"><a href="#rfc.section.9.15">9.15</a>&nbsp;<a id="header.content-encoding" href="#header.content-encoding">Content-Encoding</a></h2>
    3010       <p id="rfc.section.9.15.p.1">The "Content-Encoding" header field indicates what content-codings have been applied to the representation beyond those inherent
    3011          in the media type, and thus what decoding mechanisms have to be applied in order to obtain the media-type referenced by the
    3012          Content-Type header field. Content-Encoding is primarily used to allow a representation to be compressed without losing the
    3013          identity of its underlying media type.
    3014       </p>
    3015       <div id="rfc.figure.u.56"></div><pre class="inline"><span id="rfc.iref.g.58"></span>  <a href="#header.content-encoding" class="smpl">Content-Encoding</a> = 1#<a href="#content.codings" class="smpl">content-coding</a>
    3016 </pre><p id="rfc.section.9.15.p.3">Content codings are defined in <a href="#content.codings" title="Content Codings">Section&nbsp;5.4</a>. An example of its use is
    3017       </p>
    3018       <div id="rfc.figure.u.57"></div><pre class="text">  Content-Encoding: gzip
    3019 </pre><p id="rfc.section.9.15.p.5">The content-coding is a characteristic of the representation. Typically, the representation body is stored with this encoding
    3020          and is only decoded before rendering or analogous usage. However, a transforming proxy <em class="bcp14">MAY</em> modify the content-coding if the new coding is known to be acceptable to the recipient, unless the "no-transform" cache-control
    3021          directive is present in the message.
    3022       </p>
    3023       <p id="rfc.section.9.15.p.6">If the media type includes an inherent encoding, such as a data format that is always compressed, then that encoding would
    3024          not be restated as a Content-Encoding even if it happens to be the same algorithm as one of the content-codings. Such a content-coding
    3025          would only be listed if, for some bizarre reason, it is applied a second time to form the representation. Likewise, an origin
    3026          server might choose to publish the same payload data as multiple representations that differ only in whether the coding is
    3027          defined as part of Content-Type or Content-Encoding, since some user agents will behave differently in their handling of each
    3028          response (e.g., open a "Save as ..." dialog instead of automatic decompression and rendering of content).
    3029       </p>
    3030       <p id="rfc.section.9.15.p.7">A representation that has a content-coding applied to it <em class="bcp14">MUST</em> include a Content-Encoding header field (<a href="#header.content-encoding" id="rfc.xref.header.content-encoding.3" title="Content-Encoding">Section&nbsp;9.15</a>) that lists the content-coding(s) applied.
    3031       </p>
    3032       <p id="rfc.section.9.15.p.8">If multiple encodings have been applied to a representation, the content codings <em class="bcp14">MUST</em> be listed in the order in which they were applied. Additional information about the encoding parameters <em class="bcp14">MAY</em> be provided by other header fields not defined by this specification.
    3033       </p>
    3034       <p id="rfc.section.9.15.p.9">If the content-coding of a representation in a request message is not acceptable to the origin server, the server <em class="bcp14">SHOULD</em> respond with a status code of 415 (Unsupported Media Type).
    3035       </p>
    3036       <div id="rfc.iref.c.8"></div>
    3037       <div id="rfc.iref.h.17"></div>
    3038       <h2 id="rfc.section.9.16"><a href="#rfc.section.9.16">9.16</a>&nbsp;<a id="header.content-language" href="#header.content-language">Content-Language</a></h2>
    3039       <p id="rfc.section.9.16.p.1">The "Content-Language" header field describes the natural language(s) of the intended audience for the representation. Note
    3040          that this might not be equivalent to all the languages used within the representation.
    3041       </p>
    3042       <div id="rfc.figure.u.58"></div><pre class="inline"><span id="rfc.iref.g.59"></span>  <a href="#header.content-language" class="smpl">Content-Language</a> = 1#<a href="#language.tags" class="smpl">language-tag</a>
    3043 </pre><p id="rfc.section.9.16.p.3">Language tags are defined in <a href="#language.tags" title="Language Tags">Section&nbsp;5.6</a>. The primary purpose of Content-Language is to allow a user to identify and differentiate representations according to the
    3044          user's own preferred language. Thus, if the body content is intended only for a Danish-literate audience, the appropriate
    3045          field is
    3046       </p>
    3047       <div id="rfc.figure.u.59"></div><pre class="text">  Content-Language: da
    3048 </pre><p id="rfc.section.9.16.p.5">If no Content-Language is specified, the default is that the content is intended for all language audiences. This might mean
    3049          that the sender does not consider it to be specific to any natural language, or that the sender does not know for which language
    3050          it is intended.
    3051       </p>
    3052       <p id="rfc.section.9.16.p.6">Multiple languages <em class="bcp14">MAY</em> be listed for content that is intended for multiple audiences. For example, a rendition of the "Treaty of Waitangi", presented
    3053          simultaneously in the original Maori and English versions, would call for
    3054       </p>
    3055       <div id="rfc.figure.u.60"></div><pre class="text">  Content-Language: mi, en
    3056 </pre><p id="rfc.section.9.16.p.8">However, just because multiple languages are present within a representation does not mean that it is intended for multiple
    3057          linguistic audiences. An example would be a beginner's language primer, such as "A First Lesson in Latin", which is clearly
    3058          intended to be used by an English-literate audience. In this case, the Content-Language would properly only include "en".
    3059       </p>
    3060       <p id="rfc.section.9.16.p.9">Content-Language <em class="bcp14">MAY</em> be applied to any media type — it is not limited to textual documents.
    3061       </p>
    3062       <div id="rfc.iref.c.9"></div>
    3063       <div id="rfc.iref.h.18"></div>
    3064       <h2 id="rfc.section.9.17"><a href="#rfc.section.9.17">9.17</a>&nbsp;<a id="header.content-location" href="#header.content-location">Content-Location</a></h2>
    3065       <p id="rfc.section.9.17.p.1">The "Content-Location" header field supplies a URI that can be used as a specific identifier for the representation in this
    3066          message. In other words, if one were to perform a GET on this URI at the time of this message's generation, then a 200 response
    3067          would contain the same representation that is enclosed as payload in this message.
    3068       </p>
    3069       <div id="rfc.figure.u.61"></div><pre class="inline"><span id="rfc.iref.g.60"></span>  <a href="#header.content-location" class="smpl">Content-Location</a> = <a href="#abnf.dependencies" class="smpl">absolute-URI</a> / <a href="#abnf.dependencies" class="smpl">partial-URI</a>
    3070 </pre><p id="rfc.section.9.17.p.3">The Content-Location value is not a replacement for the effective Request URI (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.51"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>). It is representation metadata. It has the same syntax and semantics as the header field of the same name defined for MIME
    3071          body parts in <a href="http://tools.ietf.org/html/rfc2557#section-4">Section 4</a> of <a href="#RFC2557" id="rfc.xref.RFC2557.1"><cite title="MIME Encapsulation of Aggregate Documents, such as HTML (MHTML)">[RFC2557]</cite></a>. However, its appearance in an HTTP message has some special implications for HTTP recipients.
    3072       </p>
    3073       <p id="rfc.section.9.17.p.4">If Content-Location is included in a response message and its value is the same as the effective request URI, then the response
    3074          payload <em class="bcp14">SHOULD</em> be considered a current representation of that resource. For a GET or HEAD request, this is the same as the default semantics
    3075          when no Content-Location is provided by the server. For a state-changing request like PUT or POST, it implies that the server's
    3076          response contains the new representation of that resource, thereby distinguishing it from representations that might only
    3077          report about the action (e.g., "It worked!"). This allows authoring applications to update their local copies without the
    3078          need for a subsequent GET request.
    3079       </p>
    3080       <p id="rfc.section.9.17.p.5">If Content-Location is included in a response message and its value differs from the effective request URI, then the origin
    3081          server is informing recipients that this representation has its own, presumably more specific, identifier. For a GET or HEAD
    3082          request, this is an indication that the effective request URI identifies a resource that is subject to content negotiation
    3083          and the selected representation for this response can also be found at the identified URI. For other methods, such a Content-Location
    3084          indicates that this representation contains a report on the action's status and the same report is available (for future access
    3085          with GET) at the given URI. For example, a purchase transaction made via a POST request might include a receipt document as
    3086          the payload of the 200 response; the Content-Location value provides an identifier for retrieving a copy of that same receipt
    3087          in the future.
    3088       </p>
    3089       <p id="rfc.section.9.17.p.6">If Content-Location is included in a request message, then it <em class="bcp14">MAY</em> be interpreted by the origin server as an indication of where the user agent originally obtained the content of the enclosed
    3090          representation (prior to any subsequent modification of the content by that user agent). In other words, the user agent is
    3091          providing the same representation metadata that it received with the original representation. However, such interpretation <em class="bcp14">MUST NOT</em> be used to alter the semantics of the method requested by the client. For example, if a client makes a PUT request on a negotiated
    3092          resource and the origin server accepts that PUT (without redirection), then the new set of values for that resource is expected
    3093          to be consistent with the one representation supplied in that PUT; the Content-Location cannot be used as a form of reverse
    3094          content selection that identifies only one of the negotiated representations to be updated. If the user agent had wanted the
    3095          latter semantics, it would have applied the PUT directly to the Content-Location URI.
    3096       </p>
    3097       <p id="rfc.section.9.17.p.7">A Content-Location field received in a request message is transitory information that <em class="bcp14">SHOULD NOT</em> be saved with other representation metadata for use in later responses. The Content-Location's value might be saved for use
    3098          in other contexts, such as within source links or other metadata.
    3099       </p>
    3100       <p id="rfc.section.9.17.p.8">A cache cannot assume that a representation with a Content-Location different from the URI used to retrieve it can be used
    3101          to respond to later requests on that Content-Location URI.
    3102       </p>
    3103       <p id="rfc.section.9.17.p.9">If the Content-Location value is a partial URI, the partial URI is interpreted relative to the effective request URI.</p>
    3104       <div id="rfc.iref.c.10"></div>
    3105       <div id="rfc.iref.h.19"></div>
    3106       <h2 id="rfc.section.9.18"><a href="#rfc.section.9.18">9.18</a>&nbsp;<a id="header.content-type" href="#header.content-type">Content-Type</a></h2>
    3107       <p id="rfc.section.9.18.p.1">The "Content-Type" header field indicates the media type of the representation. In the case of responses to the HEAD method,
    3108          the media type is that which would have been sent had the request been a GET.
    3109       </p>
    3110       <div id="rfc.figure.u.62"></div><pre class="inline"><span id="rfc.iref.g.61"></span>  <a href="#header.content-type" class="smpl">Content-Type</a> = <a href="#media.types" class="smpl">media-type</a>
    3111 </pre><p id="rfc.section.9.18.p.3">Media types are defined in <a href="#media.types" title="Media Types">Section&nbsp;5.5</a>. An example of the field is
    3112       </p>
    3113       <div id="rfc.figure.u.63"></div><pre class="text">  Content-Type: text/html; charset=ISO-8859-4
    3114 </pre><p id="rfc.section.9.18.p.5">Further discussion of Content-Type is provided in <a href="#representation.data" title="Representation Data">Section&nbsp;7.3</a>.
    3115       </p>
    3116       <h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a>&nbsp;<a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1>
     3113      <div id="rfc.figure.u.62"></div><pre class="inline"><span id="rfc.iref.g.61"></span>  <a href="#header.user-agent" class="smpl">User-Agent</a> = <a href="#product.tokens" class="smpl">product</a> *( <a href="#core.rules" class="smpl">RWS</a> ( <a href="#product.tokens" class="smpl">product</a> / <a href="#abnf.dependencies" class="smpl">comment</a> ) )
     3114</pre><p id="rfc.section.9.18.p.7">Example:</p>
     3115      <div id="rfc.figure.u.63"></div><pre class="text">  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
     3116</pre><h1 id="rfc.section.10"><a href="#rfc.section.10">10.</a>&nbsp;<a id="IANA.considerations" href="#IANA.considerations">IANA Considerations</a></h1>
    31173117      <h2 id="rfc.section.10.1"><a href="#rfc.section.10.1">10.1</a>&nbsp;<a id="method.registration" href="#method.registration">Method Registry</a></h2>
    31183118      <p id="rfc.section.10.1.p.1">The registration procedure for HTTP request methods is defined by <a href="#method.registry" title="Method Registry">Section&nbsp;2.2</a> of this document.
    … …  
    34363436                  <td class="left">http</td>
    34373437                  <td class="left">standard</td>
    3438                   <td class="left"> <a href="#header.accept" id="rfc.xref.header.accept.4" title="Accept">Section&nbsp;9.11</a>
     3438                  <td class="left"> <a href="#header.accept" id="rfc.xref.header.accept.4" title="Accept">Section&nbsp;9.1</a>
    34393439                  </td>
    34403440               </tr>
    … …  
    34433443                  <td class="left">http</td>
    34443444                  <td class="left">standard</td>
    3445                   <td class="left"> <a href="#header.accept-charset" id="rfc.xref.header.accept-charset.3" title="Accept-Charset">Section&nbsp;9.12</a>
     3445                  <td class="left"> <a href="#header.accept-charset" id="rfc.xref.header.accept-charset.3" title="Accept-Charset">Section&nbsp;9.2</a>
    34463446                  </td>
    34473447               </tr>
    … …  
    34503450                  <td class="left">http</td>
    34513451                  <td class="left">standard</td>
    3452                   <td class="left"> <a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.4" title="Accept-Encoding">Section&nbsp;9.13</a>
     3452                  <td class="left"> <a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.4" title="Accept-Encoding">Section&nbsp;9.3</a>
    34533453                  </td>
    34543454               </tr>
    … …  
    34573457                  <td class="left">http</td>
    34583458                  <td class="left">standard</td>
    3459                   <td class="left"> <a href="#header.accept-language" id="rfc.xref.header.accept-language.3" title="Accept-Language">Section&nbsp;9.14</a>
     3459                  <td class="left"> <a href="#header.accept-language" id="rfc.xref.header.accept-language.3" title="Accept-Language">Section&nbsp;9.4</a>
    34603460                  </td>
    34613461               </tr>
    … …  
    34643464                  <td class="left">http</td>
    34653465                  <td class="left">standard</td>
    3466                   <td class="left"> <a href="#header.allow" id="rfc.xref.header.allow.3" title="Allow">Section&nbsp;9.1</a>
     3466                  <td class="left"> <a href="#header.allow" id="rfc.xref.header.allow.3" title="Allow">Section&nbsp;9.5</a>
    34673467                  </td>
    34683468               </tr>
    … …  
    34713471                  <td class="left">http</td>
    34723472                  <td class="left">standard</td>
    3473                   <td class="left"> <a href="#header.content-encoding" id="rfc.xref.header.content-encoding.4" title="Content-Encoding">Section&nbsp;9.15</a>
     3473                  <td class="left"> <a href="#header.content-encoding" id="rfc.xref.header.content-encoding.4" title="Content-Encoding">Section&nbsp;9.6</a>
    34743474                  </td>
    34753475               </tr>
    … …  
    34783478                  <td class="left">http</td>
    34793479                  <td class="left">standard</td>
    3480                   <td class="left"> <a href="#header.content-language" id="rfc.xref.header.content-language.2" title="Content-Language">Section&nbsp;9.16</a>
     3480                  <td class="left"> <a href="#header.content-language" id="rfc.xref.header.content-language.2" title="Content-Language">Section&nbsp;9.7</a>
    34813481                  </td>
    34823482               </tr>
    … …  
    34853485                  <td class="left">http</td>
    34863486                  <td class="left">standard</td>
    3487                   <td class="left"> <a href="#header.content-location" id="rfc.xref.header.content-location.4" title="Content-Location">Section&nbsp;9.17</a>
     3487                  <td class="left"> <a href="#header.content-location" id="rfc.xref.header.content-location.4" title="Content-Location">Section&nbsp;9.8</a>
    34883488                  </td>
    34893489               </tr>
    … …  
    34923492                  <td class="left">http</td>
    34933493                  <td class="left">standard</td>
    3494                   <td class="left"> <a href="#header.content-type" id="rfc.xref.header.content-type.5" title="Content-Type">Section&nbsp;9.18</a>
     3494                  <td class="left"> <a href="#header.content-type" id="rfc.xref.header.content-type.5" title="Content-Type">Section&nbsp;9.9</a>
    34953495                  </td>
    34963496               </tr>
    … …  
    34993499                  <td class="left">http</td>
    35003500                  <td class="left">standard</td>
    3501                   <td class="left"> <a href="#header.date" id="rfc.xref.header.date.2" title="Date">Section&nbsp;9.2</a>
     3501                  <td class="left"> <a href="#header.date" id="rfc.xref.header.date.2" title="Date">Section&nbsp;9.10</a>
    35023502                  </td>
    35033503               </tr>
    … …  
    35063506                  <td class="left">http</td>
    35073507                  <td class="left">standard</td>
    3508                   <td class="left"> <a href="#header.expect" id="rfc.xref.header.expect.3" title="Expect">Section&nbsp;9.3</a>
     3508                  <td class="left"> <a href="#header.expect" id="rfc.xref.header.expect.3" title="Expect">Section&nbsp;9.11</a>
    35093509                  </td>
    35103510               </tr>
    … …  
    35133513                  <td class="left">http</td>
    35143514                  <td class="left">standard</td>
    3515                   <td class="left"> <a href="#header.from" id="rfc.xref.header.from.2" title="From">Section&nbsp;9.4</a>
     3515                  <td class="left"> <a href="#header.from" id="rfc.xref.header.from.2" title="From">Section&nbsp;9.12</a>
    35163516                  </td>
    35173517               </tr>
    … …  
    35203520                  <td class="left">http</td>
    35213521                  <td class="left">standard</td>
    3522                   <td class="left"> <a href="#header.location" id="rfc.xref.header.location.4" title="Location">Section&nbsp;9.5</a>
     3522                  <td class="left"> <a href="#header.location" id="rfc.xref.header.location.4" title="Location">Section&nbsp;9.13</a>
    35233523                  </td>
    35243524               </tr>
    … …  
    35343534                  <td class="left">http</td>
    35353535                  <td class="left">standard</td>
    3536                   <td class="left"> <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.4" title="Max-Forwards">Section&nbsp;9.6</a>
     3536                  <td class="left"> <a href="#header.max-forwards" id="rfc.xref.header.max-forwards.4" title="Max-Forwards">Section&nbsp;9.14</a>
    35373537                  </td>
    35383538               </tr>
    … …  
    35413541                  <td class="left">http</td>
    35423542                  <td class="left">standard</td>
    3543                   <td class="left"> <a href="#header.referer" id="rfc.xref.header.referer.2" title="Referer">Section&nbsp;9.7</a>
     3543                  <td class="left"> <a href="#header.referer" id="rfc.xref.header.referer.2" title="Referer">Section&nbsp;9.15</a>
    35443544                  </td>
    35453545               </tr>
    … …  
    35483548                  <td class="left">http</td>
    35493549                  <td class="left">standard</td>
    3550                   <td class="left"> <a href="#header.retry-after" id="rfc.xref.header.retry-after.3" title="Retry-After">Section&nbsp;9.8</a>
     3550                  <td class="left"> <a href="#header.retry-after" id="rfc.xref.header.retry-after.3" title="Retry-After">Section&nbsp;9.16</a>
    35513551                  </td>
    35523552               </tr>
    … …  
    35553555                  <td class="left">http</td>
    35563556                  <td class="left">standard</td>
    3557                   <td class="left"> <a href="#header.server" id="rfc.xref.header.server.2" title="Server">Section&nbsp;9.9</a>
     3557                  <td class="left"> <a href="#header.server" id="rfc.xref.header.server.2" title="Server">Section&nbsp;9.17</a>
    35583558                  </td>
    35593559               </tr>
    … …  
    35623562                  <td class="left">http</td>
    35633563                  <td class="left">standard</td>
    3564                   <td class="left"> <a href="#header.user-agent" id="rfc.xref.header.user-agent.3" title="User-Agent">Section&nbsp;9.10</a>
     3564                  <td class="left"> <a href="#header.user-agent" id="rfc.xref.header.user-agent.3" title="User-Agent">Section&nbsp;9.18</a>
    35653565                  </td>
    35663566               </tr>
    … …  
    36073607                  <td class="left">identity</td>
    36083608                  <td class="left">reserved (synonym for "no encoding" in Accept-Encoding header field)</td>
    3609                   <td class="left"> <a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.5" title="Accept-Encoding">Section&nbsp;9.13</a>
     3609                  <td class="left"> <a href="#header.accept-encoding" id="rfc.xref.header.accept-encoding.5" title="Accept-Encoding">Section&nbsp;9.3</a>
    36103610                  </td>
    36113611               </tr>
    … …  
    36413641         of From and Referer information.
    36423642      </p>
    3643       <p id="rfc.section.11.1.p.7">The User-Agent (<a href="#header.user-agent" id="rfc.xref.header.user-agent.4" title="User-Agent">Section&nbsp;9.10</a>) or Server (<a href="#header.server" id="rfc.xref.header.server.3" title="Server">Section&nbsp;9.9</a>) header fields can sometimes be used to determine that a specific client or server has a particular security hole which might
     3643      <p id="rfc.section.11.1.p.7">The User-Agent (<a href="#header.user-agent" id="rfc.xref.header.user-agent.4" title="User-Agent">Section&nbsp;9.18</a>) or Server (<a href="#header.server" id="rfc.xref.header.server.3" title="Server">Section&nbsp;9.17</a>) header fields can sometimes be used to determine that a specific client or server has a particular security hole which might
    36443644         be exploited. Unfortunately, this same information is often used for other valuable purposes for which HTTP currently has
    36453645         no better mechanism.
    … …  
    39943994      </p>
    39953995      <p id="rfc.section.C.p.11">Reclassify "Allow" as response header field, removing the option to specify it in a PUT request. Relax the server requirement
    3996          on the contents of the Allow header field and remove requirement on clients to always trust the header field value. (<a href="#header.allow" id="rfc.xref.header.allow.4" title="Allow">Section&nbsp;9.1</a>)
     3996         on the contents of the Allow header field and remove requirement on clients to always trust the header field value. (<a href="#header.allow" id="rfc.xref.header.allow.4" title="Allow">Section&nbsp;9.5</a>)
    39973997      </p>
    39983998      <p id="rfc.section.C.p.12">The ABNF for the Expect header field has been both fixed (allowing parameters for value-less expectations as well) and simplified
    3999          (allowing trailing semicolons after "100-continue" when they were invalid before). (<a href="#header.expect" id="rfc.xref.header.expect.4" title="Expect">Section&nbsp;9.3</a>)
     3999         (allowing trailing semicolons after "100-continue" when they were invalid before). (<a href="#header.expect" id="rfc.xref.header.expect.4" title="Expect">Section&nbsp;9.11</a>)
    40004000      </p>
    40014001      <p id="rfc.section.C.p.13">Correct syntax of Location header field to allow URI references (including relative references and fragments), as referred
    40024002         symbol "absoluteURI" wasn't what was expected, and add some clarifications as to when use of fragments would not be appropriate.
    4003          (<a href="#header.location" id="rfc.xref.header.location.5" title="Location">Section&nbsp;9.5</a>)
    4004       </p>
    4005       <p id="rfc.section.C.p.14">Restrict Max-Forwards header field to OPTIONS and TRACE (previously, extension methods could have used it as well). (<a href="#header.max-forwards" id="rfc.xref.header.max-forwards.5" title="Max-Forwards">Section&nbsp;9.6</a>)
    4006       </p>
    4007       <p id="rfc.section.C.p.15">Allow Referer field value of "about:blank" as alternative to not specifying it. (<a href="#header.referer" id="rfc.xref.header.referer.3" title="Referer">Section&nbsp;9.7</a>)
     4003         (<a href="#header.location" id="rfc.xref.header.location.5" title="Location">Section&nbsp;9.13</a>)
     4004      </p>
     4005      <p id="rfc.section.C.p.14">Restrict Max-Forwards header field to OPTIONS and TRACE (previously, extension methods could have used it as well). (<a href="#header.max-forwards" id="rfc.xref.header.max-forwards.5" title="Max-Forwards">Section&nbsp;9.14</a>)
     4006      </p>
     4007      <p id="rfc.section.C.p.15">Allow Referer field value of "about:blank" as alternative to not specifying it. (<a href="#header.referer" id="rfc.xref.header.referer.3" title="Referer">Section&nbsp;9.15</a>)
    40084008      </p>
    40094009      <p id="rfc.section.C.p.16">In the description of the Server header field, the Via field was described as a SHOULD. The requirement was and is stated
    4010          correctly in the description of the Via header field in <a href="p1-messaging.html#header.via" title="Via">Section 6.2</a> of <a href="#Part1" id="rfc.xref.Part1.57"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. (<a href="#header.server" id="rfc.xref.header.server.4" title="Server">Section&nbsp;9.9</a>)
     4010         correctly in the description of the Via header field in <a href="p1-messaging.html#header.via" title="Via">Section 6.2</a> of <a href="#Part1" id="rfc.xref.Part1.57"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>. (<a href="#header.server" id="rfc.xref.header.server.4" title="Server">Section&nbsp;9.17</a>)
    40114011      </p>
    40124012      <p id="rfc.section.C.p.17">Clarify contexts that charset is used in. (<a href="#character.sets" title="Character Encodings (charset)">Section&nbsp;5.3</a>)
    … …  
    40214021         and also because of known deficiencies in the hash algorithm itself (see <a href="#RFC6151" id="rfc.xref.RFC6151.1"><cite title="Updated Security Considerations for the MD5 Message-Digest and the HMAC-MD5 Algorithms">[RFC6151]</cite></a> for details). (<a href="#header.field.definitions" title="Header Field Definitions">Section&nbsp;9</a>)
    40224022      </p>
    4023       <p id="rfc.section.C.p.22">Remove ISO-8859-1 special-casing in Accept-Charset. (<a href="#header.accept-charset" id="rfc.xref.header.accept-charset.4" title="Accept-Charset">Section&nbsp;9.12</a>)
     4023      <p id="rfc.section.C.p.22">Remove ISO-8859-1 special-casing in Accept-Charset. (<a href="#header.accept-charset" id="rfc.xref.header.accept-charset.4" title="Accept-Charset">Section&nbsp;9.2</a>)
    40244024      </p>
    40254025      <p id="rfc.section.C.p.23">Remove base URI setting semantics for Content-Location due to poor implementation support, which was caused by too many broken
    40264026         servers emitting bogus Content-Location header fields, and also the potentially undesirable effect of potentially breaking
    4027          relative links in content-negotiated resources. (<a href="#header.content-location" id="rfc.xref.header.content-location.5" title="Content-Location">Section&nbsp;9.17</a>)
     4027         relative links in content-negotiated resources. (<a href="#header.content-location" id="rfc.xref.header.content-location.5" title="Content-Location">Section&nbsp;9.8</a>)
    40284028      </p>
    40294029      <p id="rfc.section.C.p.24">Remove reference to non-existant identity transfer-coding value tokens. (<a href="#no.content-transfer-encoding" id="rfc.xref.no.content-transfer-encoding.1" title="No Content-Transfer-Encoding">Appendix&nbsp;A.5</a>)
    … …  
    47514751            <li><a id="rfc.index.1" href="#rfc.index.1"><b>1</b></a><ul>
    47524752                  <li>100 Continue (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.100.1">4.1</a>, <a href="#rfc.iref.24"><b>4.3.1</b></a>, <a href="#rfc.xref.status.100.2">10.2</a></li>
    4753                   <li>100-continue (expect value)&nbsp;&nbsp;<a href="#rfc.iref.108"><b>9.3</b></a></li>
     4753                  <li>100-continue (expect value)&nbsp;&nbsp;<a href="#rfc.iref.137"><b>9.11</b></a></li>
    47544754                  <li>101 Switching Protocols (status code)&nbsp;&nbsp;<a href="#rfc.xref.status.101.1">4.1</a>, <a href="#rfc.iref.25"><b>4.3.2</b></a>, <a href="#rfc.xref.status.101.2">10.2</a></li>
    47554755               </ul>
    … …  
    48024802            </li>
    48034803            <li><a id="rfc.index.A" href="#rfc.index.A"><b>A</b></a><ul>
    4804                   <li>Accept header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept.1">3.2</a>, <a href="#rfc.xref.header.accept.2">5.5</a>, <a href="#rfc.xref.header.accept.3">8.1</a>, <a href="#rfc.iref.a.2"><b>9.11</b></a>, <a href="#rfc.xref.header.accept.4">10.3</a></li>
    4805                   <li>Accept-Charset header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept-charset.1">3.2</a>, <a href="#rfc.xref.header.accept-charset.2">8.1</a>, <a href="#rfc.iref.a.3"><b>9.12</b></a>, <a href="#rfc.xref.header.accept-charset.3">10.3</a>, <a href="#rfc.xref.header.accept-charset.4">C</a></li>
    4806                   <li>Accept-Encoding header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept-encoding.1">3.2</a>, <a href="#rfc.xref.header.accept-encoding.2">5.4</a>, <a href="#rfc.xref.header.accept-encoding.3">8.1</a>, <a href="#rfc.iref.a.4"><b>9.13</b></a>, <a href="#rfc.xref.header.accept-encoding.4">10.3</a>, <a href="#rfc.xref.header.accept-encoding.5">10.4</a></li>
    4807                   <li>Accept-Language header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept-language.1">3.2</a>, <a href="#rfc.xref.header.accept-language.2">8.1</a>, <a href="#rfc.iref.a.5"><b>9.14</b></a>, <a href="#rfc.xref.header.accept-language.3">10.3</a></li>
    4808                   <li>Allow header field&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">2</a>, <a href="#rfc.xref.header.allow.2">3.3</a>, <a href="#rfc.iref.a.1"><b>9.1</b></a>, <a href="#rfc.xref.header.allow.3">10.3</a>, <a href="#rfc.xref.header.allow.4">C</a></li>
     4804                  <li>Accept header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept.1">3.2</a>, <a href="#rfc.xref.header.accept.2">5.5</a>, <a href="#rfc.xref.header.accept.3">8.1</a>, <a href="#rfc.iref.a.1"><b>9.1</b></a>, <a href="#rfc.xref.header.accept.4">10.3</a></li>
     4805                  <li>Accept-Charset header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept-charset.1">3.2</a>, <a href="#rfc.xref.header.accept-charset.2">8.1</a>, <a href="#rfc.iref.a.2"><b>9.2</b></a>, <a href="#rfc.xref.header.accept-charset.3">10.3</a>, <a href="#rfc.xref.header.accept-charset.4">C</a></li>
     4806                  <li>Accept-Encoding header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept-encoding.1">3.2</a>, <a href="#rfc.xref.header.accept-encoding.2">5.4</a>, <a href="#rfc.xref.header.accept-encoding.3">8.1</a>, <a href="#rfc.iref.a.3"><b>9.3</b></a>, <a href="#rfc.xref.header.accept-encoding.4">10.3</a>, <a href="#rfc.xref.header.accept-encoding.5">10.4</a></li>
     4807                  <li>Accept-Language header field&nbsp;&nbsp;<a href="#rfc.xref.header.accept-language.1">3.2</a>, <a href="#rfc.xref.header.accept-language.2">8.1</a>, <a href="#rfc.iref.a.4"><b>9.4</b></a>, <a href="#rfc.xref.header.accept-language.3">10.3</a></li>
     4808                  <li>Allow header field&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">2</a>, <a href="#rfc.xref.header.allow.2">3.3</a>, <a href="#rfc.iref.a.5"><b>9.5</b></a>, <a href="#rfc.xref.header.allow.3">10.3</a>, <a href="#rfc.xref.header.allow.4">C</a></li>
    48094809               </ul>
    48104810            </li>
    … …  
    48204820                  <li>CONNECT method&nbsp;&nbsp;<a href="#rfc.iref.c.2"><b>2.3.8</b></a>, <a href="#rfc.xref.CONNECT.1">10.1</a>, <a href="#rfc.xref.CONNECT.2">C</a></li>
    48214821                  <li>content negotiation&nbsp;&nbsp;<a href="#rfc.iref.c.1">1.1</a></li>
    4822                   <li>Content-Encoding header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-encoding.1">5.4</a>, <a href="#rfc.xref.header.content-encoding.2">7.2</a>, <a href="#rfc.iref.c.7"><b>9.15</b></a>, <a href="#rfc.xref.header.content-encoding.3">9.15</a>, <a href="#rfc.xref.header.content-encoding.4">10.3</a></li>
    4823                   <li>Content-Language header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-language.1">7.2</a>, <a href="#rfc.iref.c.8"><b>9.16</b></a>, <a href="#rfc.xref.header.content-language.2">10.3</a></li>
    4824                   <li>Content-Location header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-location.1">2.3.4</a>, <a href="#rfc.xref.header.content-location.2">7.2</a>, <a href="#rfc.xref.header.content-location.3">9.5</a>, <a href="#rfc.iref.c.9"><b>9.17</b></a>, <a href="#rfc.xref.header.content-location.4">10.3</a>, <a href="#rfc.xref.header.content-location.5">C</a></li>
     4822                  <li>Content-Encoding header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-encoding.1">5.4</a>, <a href="#rfc.xref.header.content-encoding.2">7.2</a>, <a href="#rfc.iref.c.7"><b>9.6</b></a>, <a href="#rfc.xref.header.content-encoding.3">9.6</a>, <a href="#rfc.xref.header.content-encoding.4">10.3</a></li>
     4823                  <li>Content-Language header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-language.1">7.2</a>, <a href="#rfc.iref.c.8"><b>9.7</b></a>, <a href="#rfc.xref.header.content-language.2">10.3</a></li>
     4824                  <li>Content-Location header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-location.1">2.3.4</a>, <a href="#rfc.xref.header.content-location.2">7.2</a>, <a href="#rfc.iref.c.9"><b>9.8</b></a>, <a href="#rfc.xref.header.content-location.3">9.13</a>, <a href="#rfc.xref.header.content-location.4">10.3</a>, <a href="#rfc.xref.header.content-location.5">C</a></li>
    48254825                  <li>Content-Transfer-Encoding header field&nbsp;&nbsp;<a href="#rfc.iref.c.11">A.5</a>, <a href="#rfc.xref.no.content-transfer-encoding.1">C</a></li>
    4826                   <li>Content-Type header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-type.1">3.1</a>, <a href="#rfc.xref.header.content-type.2">4</a>, <a href="#rfc.xref.header.content-type.3">5.5</a>, <a href="#rfc.xref.header.content-type.4">7.2</a>, <a href="#rfc.iref.c.10"><b>9.18</b></a>, <a href="#rfc.xref.header.content-type.5">10.3</a></li>
     4826                  <li>Content-Type header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-type.1">3.1</a>, <a href="#rfc.xref.header.content-type.2">4</a>, <a href="#rfc.xref.header.content-type.3">5.5</a>, <a href="#rfc.xref.header.content-type.4">7.2</a>, <a href="#rfc.iref.c.10"><b>9.9</b></a>, <a href="#rfc.xref.header.content-type.5">10.3</a></li>
    48274827               </ul>
    48284828            </li>
    48294829            <li><a id="rfc.index.D" href="#rfc.index.D"><b>D</b></a><ul>
    4830                   <li>Date header field&nbsp;&nbsp;<a href="#rfc.xref.header.date.1">3.3</a>, <a href="#rfc.iref.d.3"><b>9.2</b></a>, <a href="#rfc.xref.header.date.2">10.3</a></li>
     4830                  <li>Date header field&nbsp;&nbsp;<a href="#rfc.xref.header.date.1">3.3</a>, <a href="#rfc.iref.d.3"><b>9.10</b></a>, <a href="#rfc.xref.header.date.2">10.3</a></li>
    48314831                  <li>deflate (Coding Format)&nbsp;&nbsp;<a href="#rfc.iref.d.2">5.4</a></li>
    48324832                  <li>DELETE method&nbsp;&nbsp;<a href="#rfc.iref.d.1"><b>2.3.6</b></a>, <a href="#rfc.xref.DELETE.1">10.1</a></li>
    … …  
    48354835            </li>
    48364836            <li><a id="rfc.index.E" href="#rfc.index.E"><b>E</b></a><ul>
    4837                   <li>Expect header field&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">3.2</a>, <a href="#rfc.xref.header.expect.2">4.6.14</a>, <a href="#rfc.iref.e.1"><b>9.3</b></a>, <a href="#rfc.xref.header.expect.3">10.3</a>, <a href="#rfc.xref.header.expect.4">C</a></li>
     4837                  <li>Expect header field&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">3.2</a>, <a href="#rfc.xref.header.expect.2">4.6.14</a>, <a href="#rfc.iref.e.1"><b>9.11</b></a>, <a href="#rfc.xref.header.expect.3">10.3</a>, <a href="#rfc.xref.header.expect.4">C</a></li>
    48384838                  <li>Expect Values&nbsp;&nbsp;
    48394839                     <ul>
    4840                         <li>100-continue&nbsp;&nbsp;<a href="#rfc.iref.e.2"><b>9.3</b></a></li>
     4840                        <li>100-continue&nbsp;&nbsp;<a href="#rfc.iref.e.2"><b>9.11</b></a></li>
    48414841                     </ul>
    48424842                  </li>
    … …  
    48444844            </li>
    48454845            <li><a id="rfc.index.F" href="#rfc.index.F"><b>F</b></a><ul>
    4846                   <li>From header field&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">3.2</a>, <a href="#rfc.iref.f.1"><b>9.4</b></a>, <a href="#rfc.xref.header.from.2">10.3</a></li>
     4846                  <li>From header field&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">3.2</a>, <a href="#rfc.iref.f.1"><b>9.12</b></a>, <a href="#rfc.xref.header.from.2">10.3</a></li>
    48474847               </ul>
    48484848            </li>
    … …  
    48514851                  <li><tt>Grammar</tt>&nbsp;&nbsp;
    48524852                     <ul>
    4853                         <li><tt>Accept</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.49"><b>9.11</b></a></li>
    4854                         <li><tt>Accept-Charset</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.53"><b>9.12</b></a></li>
    4855                         <li><tt>Accept-Encoding</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.54"><b>9.13</b></a></li>
    4856                         <li><tt>accept-ext</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.52"><b>9.11</b></a></li>
    4857                         <li><tt>Accept-Language</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.56"><b>9.14</b></a></li>
    4858                         <li><tt>accept-params</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.51"><b>9.11</b></a></li>
    4859                         <li><tt>Allow</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.34"><b>9.1</b></a></li>
     4853                        <li><tt>Accept</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.34"><b>9.1</b></a></li>
     4854                        <li><tt>Accept-Charset</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.38"><b>9.2</b></a></li>
     4855                        <li><tt>Accept-Encoding</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.39"><b>9.3</b></a></li>
     4856                        <li><tt>accept-ext</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.37"><b>9.1</b></a></li>
     4857                        <li><tt>Accept-Language</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.41"><b>9.4</b></a></li>
     4858                        <li><tt>accept-params</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.36"><b>9.1</b></a></li>
     4859                        <li><tt>Allow</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.43"><b>9.5</b></a></li>
    48604860                        <li><tt>asctime-date</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.21"><b>5.1</b></a></li>
    48614861                        <li><tt>attribute</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.31"><b>5.5</b></a></li>
    48624862                        <li><tt>charset</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.24"><b>5.3</b></a></li>
    4863                         <li><tt>codings</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.55"><b>9.13</b></a></li>
     4863                        <li><tt>codings</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.40"><b>9.3</b></a></li>
    48644864                        <li><tt>content-coding</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.25"><b>5.4</b></a></li>
    4865                         <li><tt>Content-Encoding</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.58"><b>9.15</b></a></li>
    4866                         <li><tt>Content-Language</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.59"><b>9.16</b></a></li>
    4867                         <li><tt>Content-Location</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.60"><b>9.17</b></a></li>
    4868                         <li><tt>Content-Type</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.61"><b>9.18</b></a></li>
    4869                         <li><tt>Date</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.35"><b>9.2</b></a></li>
     4865                        <li><tt>Content-Encoding</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.44"><b>9.6</b></a></li>
     4866                        <li><tt>Content-Language</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.45"><b>9.7</b></a></li>
     4867                        <li><tt>Content-Location</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.46"><b>9.8</b></a></li>
     4868                        <li><tt>Content-Type</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.47"><b>9.9</b></a></li>
     4869                        <li><tt>Date</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.48"><b>9.10</b></a></li>
    48704870                        <li><tt>date1</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.8"><b>5.1</b></a></li>
    48714871                        <li><tt>day</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.15"><b>5.1</b></a></li>
    48724872                        <li><tt>day-name</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.13"><b>5.1</b></a></li>
    48734873                        <li><tt>day-name-l</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.14"><b>5.1</b></a></li>
    4874                         <li><tt>delta-seconds</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.46"><b>9.8</b></a></li>
    4875                         <li><tt>Expect</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.36"><b>9.3</b></a></li>
    4876                         <li><tt>expect-name</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.40"><b>9.3</b></a></li>
    4877                         <li><tt>expect-param</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.38"><b>9.3</b></a></li>
    4878                         <li><tt>expect-value</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.39"><b>9.3</b></a></li>
    4879                         <li><tt>expectation</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.37"><b>9.3</b></a></li>
     4874                        <li><tt>delta-seconds</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.59"><b>9.16</b></a></li>
     4875                        <li><tt>Expect</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.49"><b>9.11</b></a></li>
     4876                        <li><tt>expect-name</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.53"><b>9.11</b></a></li>
     4877                        <li><tt>expect-param</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.51"><b>9.11</b></a></li>
     4878                        <li><tt>expect-value</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.52"><b>9.11</b></a></li>
     4879                        <li><tt>expectation</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.50"><b>9.11</b></a></li>
    48804880                        <li><tt>extension-code</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.4"><b>4</b></a></li>
    4881                         <li><tt>From</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.41"><b>9.4</b></a></li>
     4881                        <li><tt>From</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.54"><b>9.12</b></a></li>
    48824882                        <li><tt>GMT</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.18"><b>5.1</b></a></li>
    48834883                        <li><tt>hour</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.10"><b>5.1</b></a></li>
    48844884                        <li><tt>HTTP-date</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.6"><b>5.1</b></a></li>
    4885                         <li><tt>language-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.57"><b>9.14</b></a></li>
     4885                        <li><tt>language-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.42"><b>9.4</b></a></li>
    48864886                        <li><tt>language-tag</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.33"><b>5.6</b></a></li>
    4887                         <li><tt>Location</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.42"><b>9.5</b></a></li>
    4888                         <li><tt>Max-Forwards</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.43"><b>9.6</b></a></li>
    4889                         <li><tt>media-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.50"><b>9.11</b></a></li>
     4887                        <li><tt>Location</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.55"><b>9.13</b></a></li>
     4888                        <li><tt>Max-Forwards</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.56"><b>9.14</b></a></li>
     4889                        <li><tt>media-range</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.35"><b>9.1</b></a></li>
    48904890                        <li><tt>media-type</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.27"><b>5.5</b></a></li>
    48914891                        <li><tt>method</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.1"><b>2</b></a></li>
    … …  
    48984898                        <li><tt>product-version</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.23"><b>5.2</b></a></li>
    48994899                        <li><tt>reason-phrase</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.5"><b>4</b></a></li>
    4900                         <li><tt>Referer</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.44"><b>9.7</b></a></li>
    4901                         <li><tt>Retry-After</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.45"><b>9.8</b></a></li>
     4900                        <li><tt>Referer</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.57"><b>9.15</b></a></li>
     4901                        <li><tt>Retry-After</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.58"><b>9.16</b></a></li>
    49024902                        <li><tt>rfc1123-date</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.7"><b>5.1</b></a></li>
    49034903                        <li><tt>rfc850-date</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.20"><b>5.1</b></a></li>
    49044904                        <li><tt>second</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.12"><b>5.1</b></a></li>
    4905                         <li><tt>Server</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.47"><b>9.9</b></a></li>
     4905                        <li><tt>Server</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.60"><b>9.17</b></a></li>
    49064906                        <li><tt>status-code</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.3"><b>4</b></a></li>
    49074907                        <li><tt>subtype</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.29"><b>5.5</b></a></li>
    49084908                        <li><tt>time-of-day</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.9"><b>5.1</b></a></li>
    49094909                        <li><tt>type</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.28"><b>5.5</b></a></li>
    4910                         <li><tt>User-Agent</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.48"><b>9.10</b></a></li>
     4910                        <li><tt>User-Agent</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.61"><b>9.18</b></a></li>
    49114911                        <li><tt>value</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.32"><b>5.5</b></a></li>
    49124912                        <li><tt>year</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.17"><b>5.1</b></a></li>
    … …  
    49204920                  <li>Header Fields&nbsp;&nbsp;
    49214921                     <ul>
    4922                         <li>Accept&nbsp;&nbsp;<a href="#rfc.xref.header.accept.1">3.2</a>, <a href="#rfc.xref.header.accept.2">5.5</a>, <a href="#rfc.xref.header.accept.3">8.1</a>, <a href="#rfc.iref.h.12"><b>9.11</b></a>, <a href="#rfc.xref.header.accept.4">10.3</a></li>
    4923                         <li>Accept-Charset&nbsp;&nbsp;<a href="#rfc.xref.header.accept-charset.1">3.2</a>, <a href="#rfc.xref.header.accept-charset.2">8.1</a>, <a href="#rfc.iref.h.13"><b>9.12</b></a>, <a href="#rfc.xref.header.accept-charset.3">10.3</a>, <a href="#rfc.xref.header.accept-charset.4">C</a></li>
    4924                         <li>Accept-Encoding&nbsp;&nbsp;<a href="#rfc.xref.header.accept-encoding.1">3.2</a>, <a href="#rfc.xref.header.accept-encoding.2">5.4</a>, <a href="#rfc.xref.header.accept-encoding.3">8.1</a>, <a href="#rfc.iref.h.14"><b>9.13</b></a>, <a href="#rfc.xref.header.accept-encoding.4">10.3</a>, <a href="#rfc.xref.header.accept-encoding.5">10.4</a></li>
    4925                         <li>Accept-Language&nbsp;&nbsp;<a href="#rfc.xref.header.accept-language.1">3.2</a>, <a href="#rfc.xref.header.accept-language.2">8.1</a>, <a href="#rfc.iref.h.15"><b>9.14</b></a>, <a href="#rfc.xref.header.accept-language.3">10.3</a></li>
    4926                         <li>Allow&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">2</a>, <a href="#rfc.xref.header.allow.2">3.3</a>, <a href="#rfc.iref.h.2"><b>9.1</b></a>, <a href="#rfc.xref.header.allow.3">10.3</a>, <a href="#rfc.xref.header.allow.4">C</a></li>
    4927                         <li>Content-Encoding&nbsp;&nbsp;<a href="#rfc.xref.header.content-encoding.1">5.4</a>, <a href="#rfc.xref.header.content-encoding.2">7.2</a>, <a href="#rfc.iref.h.16"><b>9.15</b></a>, <a href="#rfc.xref.header.content-encoding.3">9.15</a>, <a href="#rfc.xref.header.content-encoding.4">10.3</a></li>
    4928                         <li>Content-Language&nbsp;&nbsp;<a href="#rfc.xref.header.content-language.1">7.2</a>, <a href="#rfc.iref.h.17"><b>9.16</b></a>, <a href="#rfc.xref.header.content-language.2">10.3</a></li>
    4929                         <li>Content-Location&nbsp;&nbsp;<a href="#rfc.xref.header.content-location.1">2.3.4</a>, <a href="#rfc.xref.header.content-location.2">7.2</a>, <a href="#rfc.xref.header.content-location.3">9.5</a>, <a href="#rfc.iref.h.18"><b>9.17</b></a>, <a href="#rfc.xref.header.content-location.4">10.3</a>, <a href="#rfc.xref.header.content-location.5">C</a></li>
     4922                        <li>Accept&nbsp;&nbsp;<a href="#rfc.xref.header.accept.1">3.2</a>, <a href="#rfc.xref.header.accept.2">5.5</a>, <a href="#rfc.xref.header.accept.3">8.1</a>, <a href="#rfc.iref.h.2"><b>9.1</b></a>, <a href="#rfc.xref.header.accept.4">10.3</a></li>
     4923                        <li>Accept-Charset&nbsp;&nbsp;<a href="#rfc.xref.header.accept-charset.1">3.2</a>, <a href="#rfc.xref.header.accept-charset.2">8.1</a>, <a href="#rfc.iref.h.3"><b>9.2</b></a>, <a href="#rfc.xref.header.accept-charset.3">10.3</a>, <a href="#rfc.xref.header.accept-charset.4">C</a></li>
     4924                        <li>Accept-Encoding&nbsp;&nbsp;<a href="#rfc.xref.header.accept-encoding.1">3.2</a>, <a href="#rfc.xref.header.accept-encoding.2">5.4</a>, <a href="#rfc.xref.header.accept-encoding.3">8.1</a>, <a href="#rfc.iref.h.4"><b>9.3</b></a>, <a href="#rfc.xref.header.accept-encoding.4">10.3</a>, <a href="#rfc.xref.header.accept-encoding.5">10.4</a></li>
     4925                        <li>Accept-Language&nbsp;&nbsp;<a href="#rfc.xref.header.accept-language.1">3.2</a>, <a href="#rfc.xref.header.accept-language.2">8.1</a>, <a href="#rfc.iref.h.5"><b>9.4</b></a>, <a href="#rfc.xref.header.accept-language.3">10.3</a></li>
     4926                        <li>Allow&nbsp;&nbsp;<a href="#rfc.xref.header.allow.1">2</a>, <a href="#rfc.xref.header.allow.2">3.3</a>, <a href="#rfc.iref.h.6"><b>9.5</b></a>, <a href="#rfc.xref.header.allow.3">10.3</a>, <a href="#rfc.xref.header.allow.4">C</a></li>
     4927                        <li>Content-Encoding&nbsp;&nbsp;<a href="#rfc.xref.header.content-encoding.1">5.4</a>, <a href="#rfc.xref.header.content-encoding.2">7.2</a>, <a href="#rfc.iref.h.7"><b>9.6</b></a>, <a href="#rfc.xref.header.content-encoding.3">9.6</a>, <a href="#rfc.xref.header.content-encoding.4">10.3</a></li>
     4928                        <li>Content-Language&nbsp;&nbsp;<a href="#rfc.xref.header.content-language.1">7.2</a>, <a href="#rfc.iref.h.8"><b>9.7</b></a>, <a href="#rfc.xref.header.content-language.2">10.3</a></li>
     4929                        <li>Content-Location&nbsp;&nbsp;<a href="#rfc.xref.header.content-location.1">2.3.4</a>, <a href="#rfc.xref.header.content-location.2">7.2</a>, <a href="#rfc.iref.h.9"><b>9.8</b></a>, <a href="#rfc.xref.header.content-location.3">9.13</a>, <a href="#rfc.xref.header.content-location.4">10.3</a>, <a href="#rfc.xref.header.content-location.5">C</a></li>
    49304930                        <li>Content-Transfer-Encoding&nbsp;&nbsp;<a href="#rfc.iref.h.21">A.5</a>, <a href="#rfc.xref.no.content-transfer-encoding.1">C</a></li>
    4931                         <li>Content-Type&nbsp;&nbsp;<a href="#rfc.xref.header.content-type.1">3.1</a>, <a href="#rfc.xref.header.content-type.2">4</a>, <a href="#rfc.xref.header.content-type.3">5.5</a>, <a href="#rfc.xref.header.content-type.4">7.2</a>, <a href="#rfc.iref.h.19"><b>9.18</b></a>, <a href="#rfc.xref.header.content-type.5">10.3</a></li>
    4932                         <li>Date&nbsp;&nbsp;<a href="#rfc.xref.header.date.1">3.3</a>, <a href="#rfc.iref.h.3"><b>9.2</b></a>, <a href="#rfc.xref.header.date.2">10.3</a></li>
    4933                         <li>Expect&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">3.2</a>, <a href="#rfc.xref.header.expect.2">4.6.14</a>, <a href="#rfc.iref.h.4"><b>9.3</b></a>, <a href="#rfc.xref.header.expect.3">10.3</a>, <a href="#rfc.xref.header.expect.4">C</a></li>
    4934                         <li>From&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">3.2</a>, <a href="#rfc.iref.h.5"><b>9.4</b></a>, <a href="#rfc.xref.header.from.2">10.3</a></li>
    4935                         <li>Location&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">2.3.4</a>, <a href="#rfc.xref.header.location.2">3.3</a>, <a href="#rfc.xref.header.location.3">4.5</a>, <a href="#rfc.iref.h.6"><b>9.5</b></a>, <a href="#rfc.xref.header.location.4">10.3</a>, <a href="#rfc.xref.header.location.5">C</a></li>
    4936                         <li>Max-Forwards&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">2.3.1</a>, <a href="#rfc.xref.header.max-forwards.2">2.3.7</a>, <a href="#rfc.xref.header.max-forwards.3">3.2</a>, <a href="#rfc.iref.h.7"><b>9.6</b></a>, <a href="#rfc.xref.header.max-forwards.4">10.3</a>, <a href="#rfc.xref.header.max-forwards.5">C</a></li>
     4931                        <li>Content-Type&nbsp;&nbsp;<a href="#rfc.xref.header.content-type.1">3.1</a>, <a href="#rfc.xref.header.content-type.2">4</a>, <a href="#rfc.xref.header.content-type.3">5.5</a>, <a href="#rfc.xref.header.content-type.4">7.2</a>, <a href="#rfc.iref.h.10"><b>9.9</b></a>, <a href="#rfc.xref.header.content-type.5">10.3</a></li>
     4932                        <li>Date&nbsp;&nbsp;<a href="#rfc.xref.header.date.1">3.3</a>, <a href="#rfc.iref.h.11"><b>9.10</b></a>, <a href="#rfc.xref.header.date.2">10.3</a></li>
     4933                        <li>Expect&nbsp;&nbsp;<a href="#rfc.xref.header.expect.1">3.2</a>, <a href="#rfc.xref.header.expect.2">4.6.14</a>, <a href="#rfc.iref.h.12"><b>9.11</b></a>, <a href="#rfc.xref.header.expect.3">10.3</a>, <a href="#rfc.xref.header.expect.4">C</a></li>
     4934                        <li>From&nbsp;&nbsp;<a href="#rfc.xref.header.from.1">3.2</a>, <a href="#rfc.iref.h.13"><b>9.12</b></a>, <a href="#rfc.xref.header.from.2">10.3</a></li>
     4935                        <li>Location&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">2.3.4</a>, <a href="#rfc.xref.header.location.2">3.3</a>, <a href="#rfc.xref.header.location.3">4.5</a>, <a href="#rfc.iref.h.14"><b>9.13</b></a>, <a href="#rfc.xref.header.location.4">10.3</a>, <a href="#rfc.xref.header.location.5">C</a></li>
     4936                        <li>Max-Forwards&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">2.3.1</a>, <a href="#rfc.xref.header.max-forwards.2">2.3.7</a>, <a href="#rfc.xref.header.max-forwards.3">3.2</a>, <a href="#rfc.iref.h.15"><b>9.14</b></a>, <a href="#rfc.xref.header.max-forwards.4">10.3</a>, <a href="#rfc.xref.header.max-forwards.5">C</a></li>
    49374937                        <li>MIME-Version&nbsp;&nbsp;<a href="#rfc.xref.mime-version.1">10.3</a>, <a href="#rfc.iref.h.20"><b>A.1</b></a></li>
    4938                         <li>Referer&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">3.2</a>, <a href="#rfc.iref.h.8"><b>9.7</b></a>, <a href="#rfc.xref.header.referer.2">10.3</a>, <a href="#rfc.xref.header.referer.3">C</a></li>
    4939                         <li>Retry-After&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">3.3</a>, <a href="#rfc.xref.header.retry-after.2">4.7.4</a>, <a href="#rfc.iref.h.9"><b>9.8</b></a>, <a href="#rfc.xref.header.retry-after.3">10.3</a></li>
    4940                         <li>Server&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">3.3</a>, <a href="#rfc.iref.h.10"><b>9.9</b></a>, <a href="#rfc.xref.header.server.2">10.3</a>, <a href="#rfc.xref.header.server.3">11.1</a>, <a href="#rfc.xref.header.server.4">C</a></li>
    4941                         <li>User-Agent&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">3.2</a>, <a href="#rfc.xref.header.user-agent.2">8.1</a>, <a href="#rfc.iref.h.11"><b>9.10</b></a>, <a href="#rfc.xref.header.user-agent.3">10.3</a>, <a href="#rfc.xref.header.user-agent.4">11.1</a></li>
     4938                        <li>Referer&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">3.2</a>, <a href="#rfc.iref.h.16"><b>9.15</b></a>, <a href="#rfc.xref.header.referer.2">10.3</a>, <a href="#rfc.xref.header.referer.3">C</a></li>
     4939                        <li>Retry-After&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">3.3</a>, <a href="#rfc.xref.header.retry-after.2">4.7.4</a>, <a href="#rfc.iref.h.17"><b>9.16</b></a>, <a href="#rfc.xref.header.retry-after.3">10.3</a></li>
     4940                        <li>Server&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">3.3</a>, <a href="#rfc.iref.h.18"><b>9.17</b></a>, <a href="#rfc.xref.header.server.2">10.3</a>, <a href="#rfc.xref.header.server.3">11.1</a>, <a href="#rfc.xref.header.server.4">C</a></li>
     4941                        <li>User-Agent&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">3.2</a>, <a href="#rfc.xref.header.user-agent.2">8.1</a>, <a href="#rfc.iref.h.19"><b>9.18</b></a>, <a href="#rfc.xref.header.user-agent.3">10.3</a>, <a href="#rfc.xref.header.user-agent.4">11.1</a></li>
    49424942                     </ul>
    49434943                  </li>
    … …  
    49494949            </li>
    49504950            <li><a id="rfc.index.L" href="#rfc.index.L"><b>L</b></a><ul>
    4951                   <li>Location header field&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">2.3.4</a>, <a href="#rfc.xref.header.location.2">3.3</a>, <a href="#rfc.xref.header.location.3">4.5</a>, <a href="#rfc.iref.l.1"><b>9.5</b></a>, <a href="#rfc.xref.header.location.4">10.3</a>, <a href="#rfc.xref.header.location.5">C</a></li>
     4951                  <li>Location header field&nbsp;&nbsp;<a href="#rfc.xref.header.location.1">2.3.4</a>, <a href="#rfc.xref.header.location.2">3.3</a>, <a href="#rfc.xref.header.location.3">4.5</a>, <a href="#rfc.iref.l.1"><b>9.13</b></a>, <a href="#rfc.xref.header.location.4">10.3</a>, <a href="#rfc.xref.header.location.5">C</a></li>
    49524952               </ul>
    49534953            </li>
    49544954            <li><a id="rfc.index.M" href="#rfc.index.M"><b>M</b></a><ul>
    4955                   <li>Max-Forwards header field&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">2.3.1</a>, <a href="#rfc.xref.header.max-forwards.2">2.3.7</a>, <a href="#rfc.xref.header.max-forwards.3">3.2</a>, <a href="#rfc.iref.m.9"><b>9.6</b></a>, <a href="#rfc.xref.header.max-forwards.4">10.3</a>, <a href="#rfc.xref.header.max-forwards.5">C</a></li>
     4955                  <li>Max-Forwards header field&nbsp;&nbsp;<a href="#rfc.xref.header.max-forwards.1">2.3.1</a>, <a href="#rfc.xref.header.max-forwards.2">2.3.7</a>, <a href="#rfc.xref.header.max-forwards.3">3.2</a>, <a href="#rfc.iref.m.9"><b>9.14</b></a>, <a href="#rfc.xref.header.max-forwards.4">10.3</a>, <a href="#rfc.xref.header.max-forwards.5">C</a></li>
    49564956                  <li>Methods&nbsp;&nbsp;
    49574957                     <ul>
    … …  
    49604960                        <li>GET&nbsp;&nbsp;<a href="#rfc.iref.m.2"><b>2.3.2</b></a>, <a href="#rfc.xref.GET.1">10.1</a></li>
    49614961                        <li>HEAD&nbsp;&nbsp;<a href="#rfc.iref.m.3"><b>2.3.3</b></a>, <a href="#rfc.xref.HEAD.1">10.1</a></li>
    4962                         <li>OPTIONS&nbsp;&nbsp;<a href="#rfc.iref.m.1"><b>2.3.1</b></a>, <a href="#rfc.xref.OPTIONS.1">9.6</a>, <a href="#rfc.xref.OPTIONS.2">10.1</a></li>
     4962                        <li>OPTIONS&nbsp;&nbsp;<a href="#rfc.iref.m.1"><b>2.3.1</b></a>, <a href="#rfc.xref.OPTIONS.1">9.14</a>, <a href="#rfc.xref.OPTIONS.2">10.1</a></li>
    49634963                        <li>POST&nbsp;&nbsp;<a href="#rfc.iref.m.4"><b>2.3.4</b></a>, <a href="#rfc.xref.POST.1">10.1</a>, <a href="#rfc.xref.POST.2">C</a></li>
    49644964                        <li>PUT&nbsp;&nbsp;<a href="#rfc.iref.m.5"><b>2.3.5</b></a>, <a href="#rfc.xref.PUT.1">10.1</a>, <a href="#rfc.xref.PUT.2">C</a></li>
    4965                         <li>TRACE&nbsp;&nbsp;<a href="#rfc.iref.m.7"><b>2.3.7</b></a>, <a href="#rfc.xref.TRACE.1">9.6</a>, <a href="#rfc.xref.TRACE.2">10.1</a>, <a href="#rfc.xref.TRACE.3">11.1</a></li>
     4965                        <li>TRACE&nbsp;&nbsp;<a href="#rfc.iref.m.7"><b>2.3.7</b></a>, <a href="#rfc.xref.TRACE.1">9.14</a>, <a href="#rfc.xref.TRACE.2">10.1</a>, <a href="#rfc.xref.TRACE.3">11.1</a></li>
    49664966                     </ul>
    49674967                  </li>
    … …  
    49704970            </li>
    49714971            <li><a id="rfc.index.O" href="#rfc.index.O"><b>O</b></a><ul>
    4972                   <li>OPTIONS method&nbsp;&nbsp;<a href="#rfc.iref.o.1"><b>2.3.1</b></a>, <a href="#rfc.xref.OPTIONS.1">9.6</a>, <a href="#rfc.xref.OPTIONS.2">10.1</a></li>
     4972                  <li>OPTIONS method&nbsp;&nbsp;<a href="#rfc.iref.o.1"><b>2.3.1</b></a>, <a href="#rfc.xref.OPTIONS.1">9.14</a>, <a href="#rfc.xref.OPTIONS.2">10.1</a></li>
    49734973               </ul>
    49744974            </li>
    49754975            <li><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul>
    4976                   <li><em>Part1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1</a>, <a href="#rfc.xref.Part1.2">1.2</a>, <a href="#rfc.xref.Part1.3">1.3</a>, <a href="#rfc.xref.Part1.4">1.3.1</a>, <a href="#rfc.xref.Part1.5">1.3.1</a>, <a href="#rfc.xref.Part1.6">1.3.1</a>, <a href="#rfc.xref.Part1.7">1.3.1</a>, <a href="#rfc.xref.Part1.8">1.3.1</a>, <a href="#rfc.xref.Part1.9">1.3.1</a>, <a href="#rfc.xref.Part1.10">1.3.1</a>, <a href="#rfc.xref.Part1.11">1.3.1</a>, <a href="#rfc.xref.Part1.12">1.3.2</a>, <a href="#rfc.xref.Part1.13">1.3.2</a>, <a href="#rfc.xref.Part1.14">1.3.2</a>, <a href="#rfc.xref.Part1.15">1.3.2</a>, <a href="#rfc.xref.Part1.16">1.3.2</a>, <a href="#rfc.xref.Part1.17">2</a>, <a href="#rfc.xref.Part1.18">2.2.1</a>, <a href="#rfc.xref.Part1.19">2.3.1</a>, <a href="#rfc.xref.Part1.20">2.3.7</a>, <a href="#rfc.xref.Part1.21">2.3.7</a>, <a href="#rfc.xref.Part1.22">2.3.8</a>, <a href="#rfc.xref.Part1.23">3</a>, <a href="#rfc.xref.Part1.24">3.1</a>, <a href="#rfc.xref.Part1.25">3.1</a>, <a href="#rfc.xref.Part1.26">3.1</a>, <a href="#rfc.xref.Part1.27">3.1</a>, <a href="#rfc.xref.Part1.28">3.1</a>, <a href="#rfc.xref.Part1.29">3.2</a>, <a href="#rfc.xref.Part1.30">3.2</a>, <a href="#rfc.xref.Part1.31">3.3</a>, <a href="#rfc.xref.Part1.32">4.3.1</a>, <a href="#rfc.xref.Part1.33">4.3.2</a>, <a href="#rfc.xref.Part1.34">4.4.4</a>, <a href="#rfc.xref.Part1.35">4.4.6</a>, <a href="#rfc.xref.Part1.36">4.6.15</a>, <a href="#rfc.xref.Part1.37">4.7.6</a>, <a href="#rfc.xref.Part1.38">5.4</a>, <a href="#rfc.xref.Part1.39">5.4</a>, <a href="#rfc.xref.Part1.40">5.4</a>, <a href="#rfc.xref.Part1.41">5.4.1</a>, <a href="#rfc.xref.Part1.42">5.4.1</a>, <a href="#rfc.xref.Part1.43">6.1</a>, <a href="#rfc.xref.Part1.44">6.2</a>, <a href="#rfc.xref.Part1.45">7</a>, <a href="#rfc.xref.Part1.46">7.1</a>, <a href="#rfc.xref.Part1.47">9.3</a>, <a href="#rfc.xref.Part1.48">9.9</a>, <a href="#rfc.xref.Part1.49">9.9</a>, <a href="#rfc.xref.Part1.50">9.10</a>, <a href="#rfc.xref.Part1.51">9.17</a>, <a href="#rfc.xref.Part1.52">10.4</a>, <a href="#rfc.xref.Part1.53">10.4</a>, <a href="#rfc.xref.Part1.54">10.4</a>, <a href="#rfc.xref.Part1.55">12</a>, <a href="#Part1"><b>13.1</b></a>, <a href="#rfc.xref.Part1.56">A.6</a>, <a href="#rfc.xref.Part1.57">C</a><ul>
     4976                  <li><em>Part1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1</a>, <a href="#rfc.xref.Part1.2">1.2</a>, <a href="#rfc.xref.Part1.3">1.3</a>, <a href="#rfc.xref.Part1.4">1.3.1</a>, <a href="#rfc.xref.Part1.5">1.3.1</a>, <a href="#rfc.xref.Part1.6">1.3.1</a>, <a href="#rfc.xref.Part1.7">1.3.1</a>, <a href="#rfc.xref.Part1.8">1.3.1</a>, <a href="#rfc.xref.Part1.9">1.3.1</a>, <a href="#rfc.xref.Part1.10">1.3.1</a>, <a href="#rfc.xref.Part1.11">1.3.1</a>, <a href="#rfc.xref.Part1.12">1.3.2</a>, <a href="#rfc.xref.Part1.13">1.3.2</a>, <a href="#rfc.xref.Part1.14">1.3.2</a>, <a href="#rfc.xref.Part1.15">1.3.2</a>, <a href="#rfc.xref.Part1.16">1.3.2</a>, <a href="#rfc.xref.Part1.17">2</a>, <a href="#rfc.xref.Part1.18">2.2.1</a>, <a href="#rfc.xref.Part1.19">2.3.1</a>, <a href="#rfc.xref.Part1.20">2.3.7</a>, <a href="#rfc.xref.Part1.21">2.3.7</a>, <a href="#rfc.xref.Part1.22">2.3.8</a>, <a href="#rfc.xref.Part1.23">3</a>, <a href="#rfc.xref.Part1.24">3.1</a>, <a href="#rfc.xref.Part1.25">3.1</a>, <a href="#rfc.xref.Part1.26">3.1</a>, <a href="#rfc.xref.Part1.27">3.1</a>, <a href="#rfc.xref.Part1.28">3.1</a>, <a href="#rfc.xref.Part1.29">3.2</a>, <a href="#rfc.xref.Part1.30">3.2</a>, <a href="#rfc.xref.Part1.31">3.3</a>, <a href="#rfc.xref.Part1.32">4.3.1</a>, <a href="#rfc.xref.Part1.33">4.3.2</a>, <a href="#rfc.xref.Part1.34">4.4.4</a>, <a href="#rfc.xref.Part1.35">4.4.6</a>, <a href="#rfc.xref.Part1.36">4.6.15</a>, <a href="#rfc.xref.Part1.37">4.7.6</a>, <a href="#rfc.xref.Part1.38">5.4</a>, <a href="#rfc.xref.Part1.39">5.4</a>, <a href="#rfc.xref.Part1.40">5.4</a>, <a href="#rfc.xref.Part1.41">5.4.1</a>, <a href="#rfc.xref.Part1.42">5.4.1</a>, <a href="#rfc.xref.Part1.43">6.1</a>, <a href="#rfc.xref.Part1.44">6.2</a>, <a href="#rfc.xref.Part1.45">7</a>, <a href="#rfc.xref.Part1.46">7.1</a>, <a href="#rfc.xref.Part1.47">9.8</a>, <a href="#rfc.xref.Part1.48">9.11</a>, <a href="#rfc.xref.Part1.49">9.17</a>, <a href="#rfc.xref.Part1.50">9.17</a>, <a href="#rfc.xref.Part1.51">9.18</a>, <a href="#rfc.xref.Part1.52">10.4</a>, <a href="#rfc.xref.Part1.53">10.4</a>, <a href="#rfc.xref.Part1.54">10.4</a>, <a href="#rfc.xref.Part1.55">12</a>, <a href="#Part1"><b>13.1</b></a>, <a href="#rfc.xref.Part1.56">A.6</a>, <a href="#rfc.xref.Part1.57">C</a><ul>
    49774977                        <li><em>Section 1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.3">1.3</a></li>
    49784978                        <li><em>Section 2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.2">1.2</a></li>
    … …  
    49814981                        <li><em>Section 2.7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.12">1.3.2</a>, <a href="#rfc.xref.Part1.14">1.3.2</a>, <a href="#rfc.xref.Part1.16">1.3.2</a></li>
    49824982                        <li><em>Section 3.2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.5">1.3.1</a>, <a href="#rfc.xref.Part1.6">1.3.1</a>, <a href="#rfc.xref.Part1.7">1.3.1</a></li>
    4983                         <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.23">3</a>, <a href="#rfc.xref.Part1.26">3.1</a>, <a href="#rfc.xref.Part1.48">9.9</a>, <a href="#rfc.xref.Part1.50">9.10</a></li>
     4983                        <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.23">3</a>, <a href="#rfc.xref.Part1.26">3.1</a>, <a href="#rfc.xref.Part1.49">9.17</a>, <a href="#rfc.xref.Part1.51">9.18</a></li>
    49844984                        <li><em>Section 3.2.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.8">1.3.1</a>, <a href="#rfc.xref.Part1.9">1.3.1</a>, <a href="#rfc.xref.Part1.10">1.3.1</a>, <a href="#rfc.xref.Part1.11">1.3.1</a>, <a href="#rfc.xref.Part1.13">1.3.2</a>, <a href="#rfc.xref.Part1.25">3.1</a></li>
    49854985                        <li><em>Section 3.2.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.24">3.1</a></li>
    … …  
    49974997                        <li><em>Section 5.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.19">2.3.1</a>, <a href="#rfc.xref.Part1.22">2.3.8</a></li>
    49984998                        <li><em>Section 5.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.29">3.2</a></li>
    4999                         <li><em>Section 5.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.17">2</a>, <a href="#rfc.xref.Part1.31">3.3</a>, <a href="#rfc.xref.Part1.46">7.1</a>, <a href="#rfc.xref.Part1.51">9.17</a></li>
     4999                        <li><em>Section 5.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.17">2</a>, <a href="#rfc.xref.Part1.31">3.3</a>, <a href="#rfc.xref.Part1.46">7.1</a>, <a href="#rfc.xref.Part1.47">9.8</a></li>
    50005000                        <li><em>Section 6.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.27">3.1</a></li>
    5001                         <li><em>Section 6.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.20">2.3.7</a>, <a href="#rfc.xref.Part1.49">9.9</a>, <a href="#rfc.xref.Part1.57">C</a></li>
    5002                         <li><em>Section 6.4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.32">4.3.1</a>, <a href="#rfc.xref.Part1.47">9.3</a></li>
     5001                        <li><em>Section 6.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.20">2.3.7</a>, <a href="#rfc.xref.Part1.50">9.17</a>, <a href="#rfc.xref.Part1.57">C</a></li>
     5002                        <li><em>Section 6.4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.32">4.3.1</a>, <a href="#rfc.xref.Part1.48">9.11</a></li>
    50035003                        <li><em>Section 6.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.33">4.3.2</a>, <a href="#rfc.xref.Part1.36">4.6.15</a></li>
    50045004                        <li><em>Section 7.3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.21">2.3.7</a></li>
    … …  
    50565056            </li>
    50575057            <li><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul>
    5058                   <li>Referer header field&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">3.2</a>, <a href="#rfc.iref.r.2"><b>9.7</b></a>, <a href="#rfc.xref.header.referer.2">10.3</a>, <a href="#rfc.xref.header.referer.3">C</a></li>
     5058                  <li>Referer header field&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">3.2</a>, <a href="#rfc.iref.r.2"><b>9.15</b></a>, <a href="#rfc.xref.header.referer.2">10.3</a>, <a href="#rfc.xref.header.referer.3">C</a></li>
    50595059                  <li>representation&nbsp;&nbsp;<a href="#rfc.iref.r.1">7</a></li>
    5060                   <li>Retry-After header field&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">3.3</a>, <a href="#rfc.xref.header.retry-after.2">4.7.4</a>, <a href="#rfc.iref.r.3"><b>9.8</b></a>, <a href="#rfc.xref.header.retry-after.3">10.3</a></li>
     5060                  <li>Retry-After header field&nbsp;&nbsp;<a href="#rfc.xref.header.retry-after.1">3.3</a>, <a href="#rfc.xref.header.retry-after.2">4.7.4</a>, <a href="#rfc.iref.r.3"><b>9.16</b></a>, <a href="#rfc.xref.header.retry-after.3">10.3</a></li>
    50615061                  <li><em>RFC1123</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC1123.1">5.1</a>, <a href="#rfc.xref.RFC1123.2">5.1</a>, <a href="#RFC1123"><b>13.2</b></a><ul>
    50625062                        <li><em>Section 5.2.14</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC1123.2">5.1</a></li>
    … …  
    50905090                  <li><em>RFC2295</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2295.1">8</a>, <a href="#RFC2295"><b>13.1</b></a></li>
    50915091                  <li><em>RFC2388</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2388.1">5.5.2</a>, <a href="#RFC2388"><b>13.2</b></a></li>
    5092                   <li><em>RFC2557</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2557.1">9.17</a>, <a href="#RFC2557"><b>13.2</b></a>, <a href="#rfc.xref.RFC2557.2">A.7</a><ul>
    5093                         <li><em>Section 4</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2557.1">9.17</a></li>
     5092                  <li><em>RFC2557</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2557.1">9.8</a>, <a href="#RFC2557"><b>13.2</b></a>, <a href="#rfc.xref.RFC2557.2">A.7</a><ul>
     5093                        <li><em>Section 4</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2557.1">9.8</a></li>
    50945094                     </ul>
    50955095                  </li>
    5096                   <li><em>RFC2616</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.1">1</a>, <a href="#rfc.xref.RFC2616.2">4.5</a>, <a href="#rfc.xref.RFC2616.3">9.14</a>, <a href="#RFC2616"><b>13.2</b></a>, <a href="#rfc.xref.RFC2616.4">E.1</a><ul>
     5096                  <li><em>RFC2616</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.1">1</a>, <a href="#rfc.xref.RFC2616.2">4.5</a>, <a href="#rfc.xref.RFC2616.3">9.4</a>, <a href="#RFC2616"><b>13.2</b></a>, <a href="#rfc.xref.RFC2616.4">E.1</a><ul>
    50975097                        <li><em>Section 10.3.8</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.2">4.5</a></li>
    5098                         <li><em>Section 14.4</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.3">9.14</a></li>
     5098                        <li><em>Section 14.4</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.3">9.4</a></li>
    50995099                     </ul>
    51005100                  </li>
    … …  
    51085108                     </ul>
    51095109                  </li>
    5110                   <li><em>RFC3986</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">9.5</a>, <a href="#rfc.xref.RFC3986.2">9.5</a>, <a href="#RFC3986"><b>13.1</b></a><ul>
    5111                         <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">9.5</a></li>
    5112                         <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.2">9.5</a></li>
     5110                  <li><em>RFC3986</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">9.13</a>, <a href="#rfc.xref.RFC3986.2">9.13</a>, <a href="#RFC3986"><b>13.1</b></a><ul>
     5111                        <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">9.13</a></li>
     5112                        <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.2">9.13</a></li>
    51135113                     </ul>
    51145114                  </li>
    51155115                  <li><em>RFC4288</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4288.1">5.5</a>, <a href="#RFC4288"><b>13.1</b></a></li>
    5116                   <li><em>RFC4647</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.1">9.14</a>, <a href="#rfc.xref.RFC4647.2">9.14</a>, <a href="#rfc.xref.RFC4647.3">9.14</a>, <a href="#rfc.xref.RFC4647.4">9.14</a>, <a href="#RFC4647"><b>13.1</b></a><ul>
    5117                         <li><em>Section 2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.1">9.14</a></li>
    5118                         <li><em>Section 2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.2">9.14</a></li>
    5119                         <li><em>Section 3</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.3">9.14</a></li>
    5120                         <li><em>Section 3.3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.4">9.14</a></li>
     5116                  <li><em>RFC4647</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.1">9.4</a>, <a href="#rfc.xref.RFC4647.2">9.4</a>, <a href="#rfc.xref.RFC4647.3">9.4</a>, <a href="#rfc.xref.RFC4647.4">9.4</a>, <a href="#RFC4647"><b>13.1</b></a><ul>
     5117                        <li><em>Section 2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.1">9.4</a></li>
     5118                        <li><em>Section 2.3</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.2">9.4</a></li>
     5119                        <li><em>Section 3</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.3">9.4</a></li>
     5120                        <li><em>Section 3.3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4647.4">9.4</a></li>
    51215121                     </ul>
    51225122                  </li>
    … …  
    51295129                     </ul>
    51305130                  </li>
    5131                   <li><em>RFC5322</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5322.1">5.1</a>, <a href="#rfc.xref.RFC5322.2">9.2</a>, <a href="#rfc.xref.RFC5322.3">9.4</a>, <a href="#rfc.xref.RFC5322.4">9.4</a>, <a href="#RFC5322"><b>13.2</b></a>, <a href="#rfc.xref.RFC5322.5">A</a><ul>
     5131                  <li><em>RFC5322</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5322.1">5.1</a>, <a href="#rfc.xref.RFC5322.2">9.10</a>, <a href="#rfc.xref.RFC5322.3">9.12</a>, <a href="#rfc.xref.RFC5322.4">9.12</a>, <a href="#RFC5322"><b>13.2</b></a>, <a href="#rfc.xref.RFC5322.5">A</a><ul>
    51325132                        <li><em>Section 3.3</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5322.1">5.1</a></li>
    5133                         <li><em>Section 3.4</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5322.3">9.4</a>, <a href="#rfc.xref.RFC5322.4">9.4</a></li>
    5134                         <li><em>Section 3.6.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5322.2">9.2</a></li>
     5133                        <li><em>Section 3.4</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5322.3">9.12</a>, <a href="#rfc.xref.RFC5322.4">9.12</a></li>
     5134                        <li><em>Section 3.6.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5322.2">9.10</a></li>
    51355135                     </ul>
    51365136                  </li>
    … …  
    51485148                  <li>Safe Methods&nbsp;&nbsp;<a href="#rfc.iref.s.2"><b>2.1.1</b></a></li>
    51495149                  <li>selected representation&nbsp;&nbsp;<a href="#rfc.iref.s.1"><b>1.1</b></a></li>
    5150                   <li>Server header field&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">3.3</a>, <a href="#rfc.iref.s.39"><b>9.9</b></a>, <a href="#rfc.xref.header.server.2">10.3</a>, <a href="#rfc.xref.header.server.3">11.1</a>, <a href="#rfc.xref.header.server.4">C</a></li>
     5150                  <li>Server header field&nbsp;&nbsp;<a href="#rfc.xref.header.server.1">3.3</a>, <a href="#rfc.iref.s.39"><b>9.17</b></a>, <a href="#rfc.xref.header.server.2">10.3</a>, <a href="#rfc.xref.header.server.3">11.1</a>, <a href="#rfc.xref.header.server.4">C</a></li>
    51515151                  <li>Status Codes&nbsp;&nbsp;
    51525152                     <ul>
    … …  
    51925192            </li>
    51935193            <li><a id="rfc.index.T" href="#rfc.index.T"><b>T</b></a><ul>
    5194                   <li>TRACE method&nbsp;&nbsp;<a href="#rfc.iref.t.1"><b>2.3.7</b></a>, <a href="#rfc.xref.TRACE.1">9.6</a>, <a href="#rfc.xref.TRACE.2">10.1</a>, <a href="#rfc.xref.TRACE.3">11.1</a></li>
     5194                  <li>TRACE method&nbsp;&nbsp;<a href="#rfc.iref.t.1"><b>2.3.7</b></a>, <a href="#rfc.xref.TRACE.1">9.14</a>, <a href="#rfc.xref.TRACE.2">10.1</a>, <a href="#rfc.xref.TRACE.3">11.1</a></li>
    51955195               </ul>
    51965196            </li>
    51975197            <li><a id="rfc.index.U" href="#rfc.index.U"><b>U</b></a><ul>
    5198                   <li>User-Agent header field&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">3.2</a>, <a href="#rfc.xref.header.user-agent.2">8.1</a>, <a href="#rfc.iref.u.1"><b>9.10</b></a>, <a href="#rfc.xref.header.user-agent.3">10.3</a>, <a href="#rfc.xref.header.user-agent.4">11.1</a></li>
     5198                  <li>User-Agent header field&nbsp;&nbsp;<a href="#rfc.xref.header.user-agent.1">3.2</a>, <a href="#rfc.xref.header.user-agent.2">8.1</a>, <a href="#rfc.iref.u.1"><b>9.18</b></a>, <a href="#rfc.xref.header.user-agent.3">10.3</a>, <a href="#rfc.xref.header.user-agent.4">11.1</a></li>
    51995199               </ul>
    52005200            </li>

  • draft-ietf-httpbis/experiment/p2-semantics.xml

    r1631 r1633  
    29112911</t>
    29122912
     2913
     2914<section title="Accept" anchor="header.accept">
     2915  <iref primary="true" item="Accept header field" x:for-anchor=""/>
     2916  <iref primary="true" item="Header Fields" subitem="Accept" x:for-anchor=""/>
     2917  <x:anchor-alias value="Accept"/>
     2918  <x:anchor-alias value="accept-ext"/>
     2919  <x:anchor-alias value="accept-params"/>
     2920  <x:anchor-alias value="media-range"/>
     2921<t>
     2922   The "Accept" header field can be used by user agents to specify
     2923   response media types that are acceptable. Accept header fields can be used to
     2924   indicate that the request is specifically limited to a small set of desired
     2925   types, as in the case of a request for an in-line image.
     2926</t>
     2927<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/>
     2928  <x:ref>Accept</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
     2929 
     2930  <x:ref>media-range</x:ref>    = ( "*/*"
     2931                   / ( <x:ref>type</x:ref> "/" "*" )
     2932                   / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
     2933                   ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
     2934  <x:ref>accept-params</x:ref>  = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> *( <x:ref>accept-ext</x:ref> )
     2935  <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref> [ "=" <x:ref>word</x:ref> ]
     2936</artwork></figure>
     2937<t>
     2938   The asterisk "*" character is used to group media types into ranges,
     2939   with "*/*" indicating all media types and "type/*" indicating all
     2940   subtypes of that type. The media-range &MAY; include media type
     2941   parameters that are applicable to that range.
     2942</t>
     2943<t>
     2944   Each media-range &MAY; be followed by one or more accept-params,
     2945   beginning with the "q" parameter for indicating a relative quality
     2946   factor. The first "q" parameter (if any) separates the media-range
     2947   parameter(s) from the accept-params. Quality factors allow the user
     2948   or user agent to indicate the relative degree of preference for that
     2949   media-range, using the qvalue scale from 0 to 1 (qvalue;). The
     2950   default value is q=1.
     2951</t>
     2952<x:note>
     2953  <t>
     2954    <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
     2955    parameters from Accept extension parameters is due to historical
     2956    practice. Although this prevents any media type parameter named
     2957    "q" from being used with a media range, such an event is believed
     2958    to be unlikely given the lack of any "q" parameters in the IANA
     2959    media type registry and the rare usage of any media type
     2960    parameters in Accept. Future media types are discouraged from
     2961    registering any parameter named "q".
     2962  </t>
     2963</x:note>
     2964<t>
     2965   The example
     2966</t>
     2967<figure><artwork type="example">
     2968  Accept: audio/*; q=0.2, audio/basic
     2969</artwork></figure>
     2970<t>
     2971   &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
     2972   type if it is the best available after an 80% mark-down in quality".
     2973</t>
     2974<t>
     2975   A request without any Accept header field implies that the user agent
     2976   will accept any media type in response.
     2977   If an Accept header field is present in a request and none of the
     2978   available representations for the response have a media type that is
     2979   listed as acceptable, the origin server &MAY; either
     2980   honor the Accept header field by sending a 406 (Not Acceptable) response
     2981   or disregard the Accept header field by treating the response as if
     2982   it is not subject to content negotiation.
     2983</t>
     2984<t>
     2985   A more elaborate example is
     2986</t>
     2987<figure><artwork type="example">
     2988  Accept: text/plain; q=0.5, text/html,
     2989          text/x-dvi; q=0.8, text/x-c
     2990</artwork></figure>
     2991<t>
     2992   Verbally, this would be interpreted as "text/html and text/x-c are
     2993   the preferred media types, but if they do not exist, then send the
     2994   text/x-dvi representation, and if that does not exist, send the text/plain
     2995   representation".
     2996</t>
     2997<t>
     2998   Media ranges can be overridden by more specific media ranges or
     2999   specific media types. If more than one media range applies to a given
     3000   type, the most specific reference has precedence. For example,
     3001</t>
     3002<figure><artwork type="example">
     3003  Accept: text/*, text/plain, text/plain;format=flowed, */*
     3004</artwork></figure>
     3005<t>
     3006   have the following precedence:
     3007   <list style="numbers">
     3008    <t>text/plain;format=flowed</t>
     3009    <t>text/plain</t>
     3010    <t>text/*</t>
     3011    <t>*/*</t>
     3012   </list>
     3013</t>
     3014<t>
     3015   The media type quality factor associated with a given type is
     3016   determined by finding the media range with the highest precedence
     3017   which matches that type. For example,
     3018</t>
     3019<figure><artwork type="example">
     3020  Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
     3021          text/html;level=2;q=0.4, */*;q=0.5
     3022</artwork></figure>
     3023<t>
     3024   would cause the following values to be associated:
     3025</t>
     3026<texttable align="left">
     3027  <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
     3028  <c>text/html;level=1</c>    <c>1</c>
     3029  <c>text/html</c>            <c>0.7</c>
     3030  <c>text/plain</c>           <c>0.3</c>
     3031  <c>image/jpeg</c>           <c>0.5</c>
     3032  <c>text/html;level=2</c>    <c>0.4</c>
     3033  <c>text/html;level=3</c>    <c>0.7</c>
     3034</texttable>
     3035<t>
     3036      <x:h>Note:</x:h> A user agent might be provided with a default set of quality
     3037      values for certain media ranges. However, unless the user agent is
     3038      a closed system which cannot interact with other rendering agents,
     3039      this default set ought to be configurable by the user.
     3040</t>
     3041</section>
     3042
     3043<section title="Accept-Charset" anchor="header.accept-charset">
     3044  <iref primary="true" item="Accept-Charset header field" x:for-anchor=""/>
     3045  <iref primary="true" item="Header Fields" subitem="Accept-Charset" x:for-anchor=""/>
     3046  <x:anchor-alias value="Accept-Charset"/>
     3047<t>
     3048   The "Accept-Charset" header field can be used by user agents to
     3049   indicate what character encodings are acceptable in a response
     3050   payload. This field allows
     3051   clients capable of understanding more comprehensive or special-purpose
     3052   character encodings to signal that capability to a server which is capable of
     3053   representing documents in those character encodings.
     3054</t>
     3055<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/>
     3056  <x:ref>Accept-Charset</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
     3057                         [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
     3058</artwork></figure>
     3059<t>
     3060   Character encoding values (a.k.a., charsets) are described in
     3061   <xref target="character.sets"/>. Each charset &MAY; be given an
     3062   associated quality value which represents the user's preference
     3063   for that charset. The default value is q=1. An example is
     3064</t>
     3065<figure><artwork type="example">
     3066  Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
     3067</artwork></figure>
     3068<t>
     3069   The special value "*", if present in the Accept-Charset field,
     3070   matches every character encoding which is not mentioned elsewhere in the
     3071   Accept-Charset field. If no "*" is present in an Accept-Charset field, then
     3072   all character encodings not explicitly mentioned get a quality value of 0.
     3073</t>
     3074<t>
     3075   A request without any Accept-Charset header field implies that the user
     3076   agent will accept any character encoding in response.
     3077   If an Accept-Charset header field is present in a request and none of the
     3078   available representations for the response have a character encoding that
     3079   is listed as acceptable, the origin server &MAY; either honor the
     3080   Accept-Charset header field by sending a 406 (Not Acceptable) response or
     3081   disregard the Accept-Charset header field by treating the response as if
     3082   it is not subject to content negotiation.
     3083</t>
     3084</section>
     3085
     3086<section title="Accept-Encoding" anchor="header.accept-encoding">
     3087  <iref primary="true" item="Accept-Encoding header field" x:for-anchor=""/>
     3088  <iref primary="true" item="Header Fields" subitem="Accept-Encoding" x:for-anchor=""/>
     3089  <x:anchor-alias value="Accept-Encoding"/>
     3090  <x:anchor-alias value="codings"/>
     3091<t>
     3092   The "Accept-Encoding" header field can be used by user agents to
     3093   indicate what response content-codings (<xref target="content.codings"/>)
     3094   are acceptable in the response.  An "identity" token is used as a synonym
     3095   for "no encoding" in order to communicate when no encoding is preferred.
     3096</t>
     3097<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="codings"/>
     3098  <x:ref>Accept-Encoding</x:ref>  = #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
     3099  <x:ref>codings</x:ref>          = <x:ref>content-coding</x:ref> / "identity" / "*"
     3100</artwork></figure>
     3101<t>
     3102   Each codings value &MAY; be given an associated quality value which
     3103   represents the preference for that encoding. The default value is q=1.
     3104</t>
     3105<t>
     3106   For example,
     3107</t>
     3108<figure><artwork type="example">
     3109  Accept-Encoding: compress, gzip
     3110  Accept-Encoding:
     3111  Accept-Encoding: *
     3112  Accept-Encoding: compress;q=0.5, gzip;q=1.0
     3113  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
     3114</artwork></figure>
     3115<t>
     3116   A server tests whether a content-coding for a given representation is
     3117   acceptable, according to an Accept-Encoding field, using these rules:
     3118  <list style="numbers">
     3119      <t>The special "*" symbol in an Accept-Encoding field matches any
     3120         available content-coding not explicitly listed in the header
     3121         field.</t>
     3122
     3123      <t>If the representation has no content-coding, then it is acceptable
     3124         by default unless specifically excluded by the Accept-Encoding field
     3125         stating either "identity;q=0" or "*;q=0" without a more specific
     3126         entry for "identity".</t>
     3127
     3128      <t>If the representation's content-coding is one of the content-codings
     3129         listed in the Accept-Encoding field, then it is acceptable unless
     3130         it is accompanied by a qvalue of 0. (As defined in qvalue;, a
     3131         qvalue of 0 means "not acceptable".)</t>
     3132
     3133      <t>If multiple content-codings are acceptable, then the acceptable
     3134         content-coding with the highest non-zero qvalue is preferred.</t>
     3135  </list>
     3136</t>
     3137<t>
     3138   An Accept-Encoding header field with a combined field-value that is empty
     3139   implies that the user agent does not want any content-coding in response.
     3140   If an Accept-Encoding header field is present in a request and none of the
     3141   available representations for the response have a content-coding that
     3142   is listed as acceptable, the origin server &SHOULD; send a response
     3143   without any content-coding.
     3144</t>
     3145<t>
     3146   A request without an Accept-Encoding header field implies that the user
     3147   agent will accept any content-coding in response, but a representation
     3148   without content-coding is preferred for compatibility with the widest
     3149   variety of user agents.
     3150</t>
     3151<x:note>
     3152  <t>
     3153    <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
     3154    associated with content-codings. This means that qvalues will not
     3155    work and are not permitted with x-gzip or x-compress.
     3156  </t>
     3157</x:note>
     3158</section>
     3159
     3160<section title="Accept-Language" anchor="header.accept-language">
     3161  <iref primary="true" item="Accept-Language header field" x:for-anchor=""/>
     3162  <iref primary="true" item="Header Fields" subitem="Accept-Language" x:for-anchor=""/>
     3163  <x:anchor-alias value="Accept-Language"/>
     3164  <x:anchor-alias value="language-range"/>
     3165<t>
     3166   The "Accept-Language" header field can be used by user agents to
     3167   indicate the set of natural languages that are preferred in the response.
     3168   Language tags are defined in <xref target="language.tags"/>.
     3169</t>
     3170<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="language-range"/>
     3171  <x:ref>Accept-Language</x:ref> =
     3172                    1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
     3173  <x:ref>language-range</x:ref>  =
     3174            &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
     3175</artwork></figure>
     3176<t>
     3177   Each language-range can be given an associated quality value which
     3178   represents an estimate of the user's preference for the languages
     3179   specified by that range. The quality value defaults to "q=1". For
     3180   example,
     3181</t>
     3182<figure><artwork type="example">
     3183  Accept-Language: da, en-gb;q=0.8, en;q=0.7
     3184</artwork></figure>
     3185<t>
     3186   would mean: "I prefer Danish, but will accept British English and
     3187   other types of English".
     3188   (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
     3189</t>
     3190<t>
     3191   For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
     3192   several matching schemes. Implementations can offer the most appropriate
     3193   matching scheme for their requirements.
     3194</t>
     3195<x:note>
     3196  <t>
     3197    <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
     3198    x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
     3199    previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
     3200  </t>
     3201</x:note>
     3202<t>
     3203   It might be contrary to the privacy expectations of the user to send
     3204   an Accept-Language header field with the complete linguistic preferences of
     3205   the user in every request. For a discussion of this issue, see
     3206   <xref target="privacy.issues.connected.to.accept.header.fields"/>.
     3207</t>
     3208<t>
     3209   As intelligibility is highly dependent on the individual user, it is
     3210   recommended that client applications make the choice of linguistic
     3211   preference available to the user. If the choice is not made
     3212   available, then the Accept-Language header field &MUST-NOT; be given in
     3213   the request.
     3214</t>
     3215<x:note>
     3216  <t>
     3217    <x:h>Note:</x:h> When making the choice of linguistic preference available to
     3218    the user, we remind implementors of  the fact that users are not
     3219    familiar with the details of language matching as described above,
     3220    and ought to be provided appropriate guidance. As an example, users
     3221    might assume that on selecting "en-gb", they will be served any
     3222    kind of English document if British English is not available. A
     3223    user agent might suggest in such a case to add "en" to get the
     3224    best matching behavior.
     3225  </t>
     3226</x:note>
     3227</section>
     3228
    29133229<section title="Allow" anchor="header.allow">
    29143230  <iref primary="true" item="Allow header field" x:for-anchor=""/>
    … …  
    29373253   understand all the methods specified in order to handle them according to
    29383254   the generic message handling rules.
     3255</t>
     3256</section>
     3257
     3258<section title="Content-Encoding" anchor="header.content-encoding">
     3259  <iref primary="true" item="Content-Encoding header field" x:for-anchor=""/>
     3260  <iref primary="true" item="Header Fields" subitem="Content-Encoding" x:for-anchor=""/>
     3261  <x:anchor-alias value="Content-Encoding"/>
     3262<t>
     3263   The "Content-Encoding" header field indicates what content-codings
     3264   have been applied to the representation beyond those inherent in the media
     3265   type, and thus what decoding mechanisms have to be applied in order to obtain
     3266   the media-type referenced by the Content-Type header field.
     3267   Content-Encoding is primarily used to allow a representation to be
     3268   compressed without losing the identity of its underlying media type.
     3269</t>
     3270<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/>
     3271  <x:ref>Content-Encoding</x:ref> = 1#<x:ref>content-coding</x:ref>
     3272</artwork></figure>
     3273<t>
     3274   Content codings are defined in <xref target="content.codings"/>. An example of its use is
     3275</t>
     3276<figure><artwork type="example">
     3277  Content-Encoding: gzip
     3278</artwork></figure>
     3279<t>
     3280   The content-coding is a characteristic of the representation.
     3281   Typically, the representation body is stored with this
     3282   encoding and is only decoded before rendering or analogous usage.
     3283   However, a transforming proxy &MAY; modify the content-coding if the
     3284   new coding is known to be acceptable to the recipient, unless the
     3285   "no-transform" cache-control directive is present in the message.
     3286</t>
     3287<t>
     3288   If the media type includes an inherent encoding, such as a data format
     3289   that is always compressed, then that encoding would not be restated as
     3290   a Content-Encoding even if it happens to be the same algorithm as one
     3291   of the content-codings.  Such a content-coding would only be listed if,
     3292   for some bizarre reason, it is applied a second time to form the
     3293   representation.  Likewise, an origin server might choose to publish the
     3294   same payload data as multiple representations that differ only in whether
     3295   the coding is defined as part of Content-Type or Content-Encoding, since
     3296   some user agents will behave differently in their handling of each
     3297   response (e.g., open a "Save as ..." dialog instead of automatic
     3298   decompression and rendering of content).
     3299</t>
     3300<t>
     3301   A representation that has a content-coding applied to it &MUST; include
     3302   a Content-Encoding header field (<xref target="header.content-encoding"/>)
     3303   that lists the content-coding(s) applied.
     3304</t>
     3305<t>
     3306   If multiple encodings have been applied to a representation, the content
     3307   codings &MUST; be listed in the order in which they were applied.
     3308   Additional information about the encoding parameters &MAY; be provided
     3309   by other header fields not defined by this specification.
     3310</t>
     3311<t>
     3312   If the content-coding of a representation in a request message is not
     3313   acceptable to the origin server, the server &SHOULD; respond with a
     3314   status code of 415 (Unsupported Media Type).
     3315</t>
     3316</section>
     3317
     3318<section title="Content-Language" anchor="header.content-language">
     3319  <iref primary="true" item="Content-Language header field" x:for-anchor=""/>
     3320  <iref primary="true" item="Header Fields" subitem="Content-Language" x:for-anchor=""/>
     3321  <x:anchor-alias value="Content-Language"/>
     3322<t>
     3323   The "Content-Language" header field describes the natural
     3324   language(s) of the intended audience for the representation. Note that this might
     3325   not be equivalent to all the languages used within the representation.
     3326</t>
     3327<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/>
     3328  <x:ref>Content-Language</x:ref> = 1#<x:ref>language-tag</x:ref>
     3329</artwork></figure>
     3330<t>
     3331   Language tags are defined in <xref target="language.tags"/>. The primary purpose of
     3332   Content-Language is to allow a user to identify and differentiate
     3333   representations according to the user's own preferred language. Thus, if the
     3334   body content is intended only for a Danish-literate audience, the
     3335   appropriate field is
     3336</t>
     3337<figure><artwork type="example">
     3338  Content-Language: da
     3339</artwork></figure>
     3340<t>
     3341   If no Content-Language is specified, the default is that the content
     3342   is intended for all language audiences. This might mean that the
     3343   sender does not consider it to be specific to any natural language,
     3344   or that the sender does not know for which language it is intended.
     3345</t>
     3346<t>
     3347   Multiple languages &MAY; be listed for content that is intended for
     3348   multiple audiences. For example, a rendition of the "Treaty of
     3349   Waitangi", presented simultaneously in the original Maori and English
     3350   versions, would call for
     3351</t>
     3352<figure><artwork type="example">
     3353  Content-Language: mi, en
     3354</artwork></figure>
     3355<t>
     3356   However, just because multiple languages are present within a representation
     3357   does not mean that it is intended for multiple linguistic audiences.
     3358   An example would be a beginner's language primer, such as "A First
     3359   Lesson in Latin", which is clearly intended to be used by an
     3360   English-literate audience. In this case, the Content-Language would
     3361   properly only include "en".
     3362</t>
     3363<t>
     3364   Content-Language &MAY; be applied to any media type &mdash; it is not
     3365   limited to textual documents.
     3366</t>
     3367</section>
     3368
     3369<section title="Content-Location" anchor="header.content-location">
     3370  <iref primary="true" item="Content-Location header field" x:for-anchor=""/>
     3371  <iref primary="true" item="Header Fields" subitem="Content-Location" x:for-anchor=""/>
     3372  <x:anchor-alias value="Content-Location"/>
     3373<t>
     3374   The "Content-Location" header field supplies a URI that can be used
     3375   as a specific identifier for the representation in this message.
     3376   In other words, if one were to perform a GET on this URI at the time
     3377   of this message's generation, then a 200 response would contain the
     3378   same representation that is enclosed as payload in this message.
     3379</t>
     3380<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/>
     3381  <x:ref>Content-Location</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
     3382</artwork></figure>
     3383<t>
     3384   The Content-Location value is not a replacement for the effective
     3385   Request URI (&effective-request-uri;).  It is representation metadata.
     3386   It has the same syntax and semantics as the header field of the same name
     3387   defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
     3388   However, its appearance in an HTTP message has some special implications
     3389   for HTTP recipients.
     3390</t>
     3391<t>
     3392   If Content-Location is included in a response message and its value
     3393   is the same as the effective request URI, then the response payload
     3394   &SHOULD; be considered a current representation of that resource.
     3395   For a GET or HEAD request, this is the same as the default semantics
     3396   when no Content-Location is provided by the server.  For a state-changing
     3397   request like PUT or POST, it implies that the server's response contains
     3398   the new representation of that resource, thereby distinguishing it from
     3399   representations that might only report about the action (e.g., "It worked!").
     3400   This allows authoring applications to update their local copies without
     3401   the need for a subsequent GET request.
     3402</t>
     3403<t>
     3404   If Content-Location is included in a response message and its value
     3405   differs from the effective request URI, then the origin server is
     3406   informing recipients that this representation has its own, presumably
     3407   more specific, identifier.  For a GET or HEAD request, this is an
     3408   indication that the effective request URI identifies a resource that
     3409   is subject to content negotiation and the selected representation for
     3410   this response can also be found at the identified URI.  For other
     3411   methods, such a Content-Location indicates that this representation
     3412   contains a report on the action's status and the same report is
     3413   available (for future access with GET) at the given URI.  For
     3414   example, a purchase transaction made via a POST request might
     3415   include a receipt document as the payload of the 200 response;
     3416   the Content-Location value provides an identifier for retrieving
     3417   a copy of that same receipt in the future.
     3418</t>
     3419<t>
     3420   If Content-Location is included in a request message, then it &MAY;
     3421   be interpreted by the origin server as an indication of where the
     3422   user agent originally obtained the content of the enclosed
     3423   representation (prior to any subsequent modification of the content
     3424   by that user agent).  In other words, the user agent is providing
     3425   the same representation metadata that it received with the original
     3426   representation.  However, such interpretation &MUST-NOT; be used to
     3427   alter the semantics of the method requested by the client.  For
     3428   example, if a client makes a PUT request on a negotiated resource
     3429   and the origin server accepts that PUT (without redirection), then the
     3430   new set of values for that resource is expected to be consistent with
     3431   the one representation supplied in that PUT; the Content-Location
     3432   cannot be used as a form of reverse content selection that
     3433   identifies only one of the negotiated representations to be updated.
     3434   If the user agent had wanted the latter semantics, it would have applied
     3435   the PUT directly to the Content-Location URI.
     3436</t>
     3437<t>
     3438   A Content-Location field received in a request message is transitory
     3439   information that &SHOULD-NOT; be saved with other representation
     3440   metadata for use in later responses.  The Content-Location's value
     3441   might be saved for use in other contexts, such as within source links
     3442   or other metadata.
     3443</t>
     3444<t>
     3445   A cache cannot assume that a representation with a Content-Location
     3446   different from the URI used to retrieve it can be used to respond to
     3447   later requests on that Content-Location URI.
     3448</t>
     3449<t>
     3450   If the Content-Location value is a partial URI, the partial URI is
     3451   interpreted relative to the effective request URI.
     3452</t>
     3453</section>
     3454
     3455<section title="Content-Type" anchor="header.content-type">
     3456  <iref primary="true" item="Content-Type header field" x:for-anchor=""/>
     3457  <iref primary="true" item="Header Fields" subitem="Content-Type" x:for-anchor=""/>
     3458  <x:anchor-alias value="Content-Type"/>
     3459<t>
     3460   The "Content-Type" header field indicates the media type of the
     3461   representation. In the case of responses to the HEAD method, the media type is
     3462   that which would have been sent had the request been a GET.
     3463</t>
     3464<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/>
     3465  <x:ref>Content-Type</x:ref> = <x:ref>media-type</x:ref>
     3466</artwork></figure>
     3467<t>
     3468   Media types are defined in <xref target="media.types"/>. An example of the field is
     3469</t>
     3470<figure><artwork type="example">
     3471  Content-Type: text/html; charset=ISO-8859-4
     3472</artwork></figure>
     3473<t>
     3474   Further discussion of Content-Type is provided in <xref target="representation.data"/>.
    29393475</t>
    29403476</section>
    … …  
    33633899  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
    33643900</artwork></figure>
    3365 </section>
    3366 
    3367 
    3368 <section title="Accept" anchor="header.accept">
    3369   <iref primary="true" item="Accept header field" x:for-anchor=""/>
    3370   <iref primary="true" item="Header Fields" subitem="Accept" x:for-anchor=""/>
    3371   <x:anchor-alias value="Accept"/>
    3372   <x:anchor-alias value="accept-ext"/>
    3373   <x:anchor-alias value="accept-params"/>
    3374   <x:anchor-alias value="media-range"/>
    3375 <t>
    3376    The "Accept" header field can be used by user agents to specify
    3377    response media types that are acceptable. Accept header fields can be used to
    3378    indicate that the request is specifically limited to a small set of desired
    3379    types, as in the case of a request for an in-line image.
    3380 </t>
    3381 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept"/><iref primary="true" item="Grammar" subitem="media-range"/><iref primary="true" item="Grammar" subitem="accept-params"/><iref primary="true" item="Grammar" subitem="accept-ext"/>
    3382   <x:ref>Accept</x:ref> = #( <x:ref>media-range</x:ref> [ <x:ref>accept-params</x:ref> ] )
    3383  
    3384   <x:ref>media-range</x:ref>    = ( "*/*"
    3385                    / ( <x:ref>type</x:ref> "/" "*" )
    3386                    / ( <x:ref>type</x:ref> "/" <x:ref>subtype</x:ref> )
    3387                    ) *( <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>parameter</x:ref> )
    3388   <x:ref>accept-params</x:ref>  = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> *( <x:ref>accept-ext</x:ref> )
    3389   <x:ref>accept-ext</x:ref>     = <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> <x:ref>token</x:ref> [ "=" <x:ref>word</x:ref> ]
    3390 </artwork></figure>
    3391 <t>
    3392    The asterisk "*" character is used to group media types into ranges,
    3393    with "*/*" indicating all media types and "type/*" indicating all
    3394    subtypes of that type. The media-range &MAY; include media type
    3395    parameters that are applicable to that range.
    3396 </t>
    3397 <t>
    3398    Each media-range &MAY; be followed by one or more accept-params,
    3399    beginning with the "q" parameter for indicating a relative quality
    3400    factor. The first "q" parameter (if any) separates the media-range
    3401    parameter(s) from the accept-params. Quality factors allow the user
    3402    or user agent to indicate the relative degree of preference for that
    3403    media-range, using the qvalue scale from 0 to 1 (qvalue;). The
    3404    default value is q=1.
    3405 </t>
    3406 <x:note>
    3407   <t>
    3408     <x:h>Note:</x:h> Use of the "q" parameter name to separate media type
    3409     parameters from Accept extension parameters is due to historical
    3410     practice. Although this prevents any media type parameter named
    3411     "q" from being used with a media range, such an event is believed
    3412     to be unlikely given the lack of any "q" parameters in the IANA
    3413     media type registry and the rare usage of any media type
    3414     parameters in Accept. Future media types are discouraged from
    3415     registering any parameter named "q".
    3416   </t>
    3417 </x:note>
    3418 <t>
    3419    The example
    3420 </t>
    3421 <figure><artwork type="example">
    3422   Accept: audio/*; q=0.2, audio/basic
    3423 </artwork></figure>
    3424 <t>
    3425    &SHOULD; be interpreted as "I prefer audio/basic, but send me any audio
    3426    type if it is the best available after an 80% mark-down in quality".
    3427 </t>
    3428 <t>
    3429    A request without any Accept header field implies that the user agent
    3430    will accept any media type in response.
    3431    If an Accept header field is present in a request and none of the
    3432    available representations for the response have a media type that is
    3433    listed as acceptable, the origin server &MAY; either
    3434    honor the Accept header field by sending a 406 (Not Acceptable) response
    3435    or disregard the Accept header field by treating the response as if
    3436    it is not subject to content negotiation.
    3437 </t>
    3438 <t>
    3439    A more elaborate example is
    3440 </t>
    3441 <figure><artwork type="example">
    3442   Accept: text/plain; q=0.5, text/html,
    3443           text/x-dvi; q=0.8, text/x-c
    3444 </artwork></figure>
    3445 <t>
    3446    Verbally, this would be interpreted as "text/html and text/x-c are
    3447    the preferred media types, but if they do not exist, then send the
    3448    text/x-dvi representation, and if that does not exist, send the text/plain
    3449    representation".
    3450 </t>
    3451 <t>
    3452    Media ranges can be overridden by more specific media ranges or
    3453    specific media types. If more than one media range applies to a given
    3454    type, the most specific reference has precedence. For example,
    3455 </t>
    3456 <figure><artwork type="example">
    3457   Accept: text/*, text/plain, text/plain;format=flowed, */*
    3458 </artwork></figure>
    3459 <t>
    3460    have the following precedence:
    3461    <list style="numbers">
    3462     <t>text/plain;format=flowed</t>
    3463     <t>text/plain</t>
    3464     <t>text/*</t>
    3465     <t>*/*</t>
    3466    </list>
    3467 </t>
    3468 <t>
    3469    The media type quality factor associated with a given type is
    3470    determined by finding the media range with the highest precedence
    3471    which matches that type. For example,
    3472 </t>
    3473 <figure><artwork type="example">
    3474   Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
    3475           text/html;level=2;q=0.4, */*;q=0.5
    3476 </artwork></figure>
    3477 <t>
    3478    would cause the following values to be associated:
    3479 </t>
    3480 <texttable align="left">
    3481   <ttcol>Media Type</ttcol><ttcol>Quality Value</ttcol>
    3482   <c>text/html;level=1</c>    <c>1</c>
    3483   <c>text/html</c>            <c>0.7</c>
    3484   <c>text/plain</c>           <c>0.3</c>
    3485   <c>image/jpeg</c>           <c>0.5</c>
    3486   <c>text/html;level=2</c>    <c>0.4</c>
    3487   <c>text/html;level=3</c>    <c>0.7</c>
    3488 </texttable>
    3489 <t>
    3490       <x:h>Note:</x:h> A user agent might be provided with a default set of quality
    3491       values for certain media ranges. However, unless the user agent is
    3492       a closed system which cannot interact with other rendering agents,
    3493       this default set ought to be configurable by the user.
    3494 </t>
    3495 </section>
    3496 
    3497 <section title="Accept-Charset" anchor="header.accept-charset">
    3498   <iref primary="true" item="Accept-Charset header field" x:for-anchor=""/>
    3499   <iref primary="true" item="Header Fields" subitem="Accept-Charset" x:for-anchor=""/>
    3500   <x:anchor-alias value="Accept-Charset"/>
    3501 <t>
    3502    The "Accept-Charset" header field can be used by user agents to
    3503    indicate what character encodings are acceptable in a response
    3504    payload. This field allows
    3505    clients capable of understanding more comprehensive or special-purpose
    3506    character encodings to signal that capability to a server which is capable of
    3507    representing documents in those character encodings.
    3508 </t>
    3509 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Charset"/>
    3510   <x:ref>Accept-Charset</x:ref> = 1#( ( <x:ref>charset</x:ref> / "*" )
    3511                          [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
    3512 </artwork></figure>
    3513 <t>
    3514    Character encoding values (a.k.a., charsets) are described in
    3515    <xref target="character.sets"/>. Each charset &MAY; be given an
    3516    associated quality value which represents the user's preference
    3517    for that charset. The default value is q=1. An example is
    3518 </t>
    3519 <figure><artwork type="example">
    3520   Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
    3521 </artwork></figure>
    3522 <t>
    3523    The special value "*", if present in the Accept-Charset field,
    3524    matches every character encoding which is not mentioned elsewhere in the
    3525    Accept-Charset field. If no "*" is present in an Accept-Charset field, then
    3526    all character encodings not explicitly mentioned get a quality value of 0.
    3527 </t>
    3528 <t>
    3529    A request without any Accept-Charset header field implies that the user
    3530    agent will accept any character encoding in response.
    3531    If an Accept-Charset header field is present in a request and none of the
    3532    available representations for the response have a character encoding that
    3533    is listed as acceptable, the origin server &MAY; either honor the
    3534    Accept-Charset header field by sending a 406 (Not Acceptable) response or
    3535    disregard the Accept-Charset header field by treating the response as if
    3536    it is not subject to content negotiation.
    3537 </t>
    3538 </section>
    3539 
    3540 <section title="Accept-Encoding" anchor="header.accept-encoding">
    3541   <iref primary="true" item="Accept-Encoding header field" x:for-anchor=""/>
    3542   <iref primary="true" item="Header Fields" subitem="Accept-Encoding" x:for-anchor=""/>
    3543   <x:anchor-alias value="Accept-Encoding"/>
    3544   <x:anchor-alias value="codings"/>
    3545 <t>
    3546    The "Accept-Encoding" header field can be used by user agents to
    3547    indicate what response content-codings (<xref target="content.codings"/>)
    3548    are acceptable in the response.  An "identity" token is used as a synonym
    3549    for "no encoding" in order to communicate when no encoding is preferred.
    3550 </t>
    3551 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Encoding"/><iref primary="true" item="Grammar" subitem="codings"/>
    3552   <x:ref>Accept-Encoding</x:ref>  = #( <x:ref>codings</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
    3553   <x:ref>codings</x:ref>          = <x:ref>content-coding</x:ref> / "identity" / "*"
    3554 </artwork></figure>
    3555 <t>
    3556    Each codings value &MAY; be given an associated quality value which
    3557    represents the preference for that encoding. The default value is q=1.
    3558 </t>
    3559 <t>
    3560    For example,
    3561 </t>
    3562 <figure><artwork type="example">
    3563   Accept-Encoding: compress, gzip
    3564   Accept-Encoding:
    3565   Accept-Encoding: *
    3566   Accept-Encoding: compress;q=0.5, gzip;q=1.0
    3567   Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
    3568 </artwork></figure>
    3569 <t>
    3570    A server tests whether a content-coding for a given representation is
    3571    acceptable, according to an Accept-Encoding field, using these rules:
    3572   <list style="numbers">
    3573       <t>The special "*" symbol in an Accept-Encoding field matches any
    3574          available content-coding not explicitly listed in the header
    3575          field.</t>
    3576 
    3577       <t>If the representation has no content-coding, then it is acceptable
    3578          by default unless specifically excluded by the Accept-Encoding field
    3579          stating either "identity;q=0" or "*;q=0" without a more specific
    3580          entry for "identity".</t>
    3581 
    3582       <t>If the representation's content-coding is one of the content-codings
    3583          listed in the Accept-Encoding field, then it is acceptable unless
    3584          it is accompanied by a qvalue of 0. (As defined in qvalue;, a
    3585          qvalue of 0 means "not acceptable".)</t>
    3586 
    3587       <t>If multiple content-codings are acceptable, then the acceptable
    3588          content-coding with the highest non-zero qvalue is preferred.</t>
    3589   </list>
    3590 </t>
    3591 <t>
    3592    An Accept-Encoding header field with a combined field-value that is empty
    3593    implies that the user agent does not want any content-coding in response.
    3594    If an Accept-Encoding header field is present in a request and none of the
    3595    available representations for the response have a content-coding that
    3596    is listed as acceptable, the origin server &SHOULD; send a response
    3597    without any content-coding.
    3598 </t>
    3599 <t>
    3600    A request without an Accept-Encoding header field implies that the user
    3601    agent will accept any content-coding in response, but a representation
    3602    without content-coding is preferred for compatibility with the widest
    3603    variety of user agents.
    3604 </t>
    3605 <x:note>
    3606   <t>
    3607     <x:h>Note:</x:h> Most HTTP/1.0 applications do not recognize or obey qvalues
    3608     associated with content-codings. This means that qvalues will not
    3609     work and are not permitted with x-gzip or x-compress.
    3610   </t>
    3611 </x:note>
    3612 </section>
    3613 
    3614 <section title="Accept-Language" anchor="header.accept-language">
    3615   <iref primary="true" item="Accept-Language header field" x:for-anchor=""/>
    3616   <iref primary="true" item="Header Fields" subitem="Accept-Language" x:for-anchor=""/>
    3617   <x:anchor-alias value="Accept-Language"/>
    3618   <x:anchor-alias value="language-range"/>
    3619 <t>
    3620    The "Accept-Language" header field can be used by user agents to
    3621    indicate the set of natural languages that are preferred in the response.
    3622    Language tags are defined in <xref target="language.tags"/>.
    3623 </t>
    3624 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Accept-Language"/><iref primary="true" item="Grammar" subitem="language-range"/>
    3625   <x:ref>Accept-Language</x:ref> =
    3626                     1#( <x:ref>language-range</x:ref> [ <x:ref>OWS</x:ref> ";" <x:ref>OWS</x:ref> "q=" <x:ref>qvalue</x:ref> ] )
    3627   <x:ref>language-range</x:ref>  =
    3628             &lt;language-range, defined in <xref target="RFC4647" x:fmt="," x:sec="2.1"/>&gt;
    3629 </artwork></figure>
    3630 <t>
    3631    Each language-range can be given an associated quality value which
    3632    represents an estimate of the user's preference for the languages
    3633    specified by that range. The quality value defaults to "q=1". For
    3634    example,
    3635 </t>
    3636 <figure><artwork type="example">
    3637   Accept-Language: da, en-gb;q=0.8, en;q=0.7
    3638 </artwork></figure>
    3639 <t>
    3640    would mean: "I prefer Danish, but will accept British English and
    3641    other types of English".
    3642    (see also <xref target="RFC4647" x:sec="2.3" x:fmt="of"/>)
    3643 </t>
    3644 <t>
    3645    For matching, <xref target="RFC4647" x:sec="3" x:fmt="of"/> defines
    3646    several matching schemes. Implementations can offer the most appropriate
    3647    matching scheme for their requirements.
    3648 </t>
    3649 <x:note>
    3650   <t>
    3651     <x:h>Note:</x:h> The "Basic Filtering" scheme (<xref target="RFC4647"
    3652     x:fmt="," x:sec="3.3.1"/>) is identical to the matching scheme that was
    3653     previously defined in <xref target="RFC2616" x:fmt="of" x:sec="14.4"/>.
    3654   </t>
    3655 </x:note>
    3656 <t>
    3657    It might be contrary to the privacy expectations of the user to send
    3658    an Accept-Language header field with the complete linguistic preferences of
    3659    the user in every request. For a discussion of this issue, see
    3660    <xref target="privacy.issues.connected.to.accept.header.fields"/>.
    3661 </t>
    3662 <t>
    3663    As intelligibility is highly dependent on the individual user, it is
    3664    recommended that client applications make the choice of linguistic
    3665    preference available to the user. If the choice is not made
    3666    available, then the Accept-Language header field &MUST-NOT; be given in
    3667    the request.
    3668 </t>
    3669 <x:note>
    3670   <t>
    3671     <x:h>Note:</x:h> When making the choice of linguistic preference available to
    3672     the user, we remind implementors of  the fact that users are not
    3673     familiar with the details of language matching as described above,
    3674     and ought to be provided appropriate guidance. As an example, users
    3675     might assume that on selecting "en-gb", they will be served any
    3676     kind of English document if British English is not available. A
    3677     user agent might suggest in such a case to add "en" to get the
    3678     best matching behavior.
    3679   </t>
    3680 </x:note>
    3681 </section>
    3682 
    3683 <section title="Content-Encoding" anchor="header.content-encoding">
    3684   <iref primary="true" item="Content-Encoding header field" x:for-anchor=""/>
    3685   <iref primary="true" item="Header Fields" subitem="Content-Encoding" x:for-anchor=""/>
    3686   <x:anchor-alias value="Content-Encoding"/>
    3687 <t>
    3688    The "Content-Encoding" header field indicates what content-codings
    3689    have been applied to the representation beyond those inherent in the media
    3690    type, and thus what decoding mechanisms have to be applied in order to obtain
    3691    the media-type referenced by the Content-Type header field.
    3692    Content-Encoding is primarily used to allow a representation to be
    3693    compressed without losing the identity of its underlying media type.
    3694 </t>
    3695 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Encoding"/>
    3696   <x:ref>Content-Encoding</x:ref> = 1#<x:ref>content-coding</x:ref>
    3697 </artwork></figure>
    3698 <t>
    3699    Content codings are defined in <xref target="content.codings"/>. An example of its use is
    3700 </t>
    3701 <figure><artwork type="example">
    3702   Content-Encoding: gzip
    3703 </artwork></figure>
    3704 <t>
    3705    The content-coding is a characteristic of the representation.
    3706    Typically, the representation body is stored with this
    3707    encoding and is only decoded before rendering or analogous usage.
    3708    However, a transforming proxy &MAY; modify the content-coding if the
    3709    new coding is known to be acceptable to the recipient, unless the
    3710    "no-transform" cache-control directive is present in the message.
    3711 </t>
    3712 <t>
    3713    If the media type includes an inherent encoding, such as a data format
    3714    that is always compressed, then that encoding would not be restated as
    3715    a Content-Encoding even if it happens to be the same algorithm as one
    3716    of the content-codings.  Such a content-coding would only be listed if,
    3717    for some bizarre reason, it is applied a second time to form the
    3718    representation.  Likewise, an origin server might choose to publish the
    3719    same payload data as multiple representations that differ only in whether
    3720    the coding is defined as part of Content-Type or Content-Encoding, since
    3721    some user agents will behave differently in their handling of each
    3722    response (e.g., open a "Save as ..." dialog instead of automatic
    3723    decompression and rendering of content).
    3724 </t>
    3725 <t>
    3726    A representation that has a content-coding applied to it &MUST; include
    3727    a Content-Encoding header field (<xref target="header.content-encoding"/>)
    3728    that lists the content-coding(s) applied.
    3729 </t>
    3730 <t>
    3731    If multiple encodings have been applied to a representation, the content
    3732    codings &MUST; be listed in the order in which they were applied.
    3733    Additional information about the encoding parameters &MAY; be provided
    3734    by other header fields not defined by this specification.
    3735 </t>
    3736 <t>
    3737    If the content-coding of a representation in a request message is not
    3738    acceptable to the origin server, the server &SHOULD; respond with a
    3739    status code of 415 (Unsupported Media Type).
    3740 </t>
    3741 </section>
    3742 
    3743 <section title="Content-Language" anchor="header.content-language">
    3744   <iref primary="true" item="Content-Language header field" x:for-anchor=""/>
    3745   <iref primary="true" item="Header Fields" subitem="Content-Language" x:for-anchor=""/>
    3746   <x:anchor-alias value="Content-Language"/>
    3747 <t>
    3748    The "Content-Language" header field describes the natural
    3749    language(s) of the intended audience for the representation. Note that this might
    3750    not be equivalent to all the languages used within the representation.
    3751 </t>
    3752 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Language"/>
    3753   <x:ref>Content-Language</x:ref> = 1#<x:ref>language-tag</x:ref>
    3754 </artwork></figure>
    3755 <t>
    3756    Language tags are defined in <xref target="language.tags"/>. The primary purpose of
    3757    Content-Language is to allow a user to identify and differentiate
    3758    representations according to the user's own preferred language. Thus, if the
    3759    body content is intended only for a Danish-literate audience, the
    3760    appropriate field is
    3761 </t>
    3762 <figure><artwork type="example">
    3763   Content-Language: da
    3764 </artwork></figure>
    3765 <t>
    3766    If no Content-Language is specified, the default is that the content
    3767    is intended for all language audiences. This might mean that the
    3768    sender does not consider it to be specific to any natural language,
    3769    or that the sender does not know for which language it is intended.
    3770 </t>
    3771 <t>
    3772    Multiple languages &MAY; be listed for content that is intended for
    3773    multiple audiences. For example, a rendition of the "Treaty of
    3774    Waitangi", presented simultaneously in the original Maori and English
    3775    versions, would call for
    3776 </t>
    3777 <figure><artwork type="example">
    3778   Content-Language: mi, en
    3779 </artwork></figure>
    3780 <t>
    3781    However, just because multiple languages are present within a representation
    3782    does not mean that it is intended for multiple linguistic audiences.
    3783    An example would be a beginner's language primer, such as "A First
    3784    Lesson in Latin", which is clearly intended to be used by an
    3785    English-literate audience. In this case, the Content-Language would
    3786    properly only include "en".
    3787 </t>
    3788 <t>
    3789    Content-Language &MAY; be applied to any media type &mdash; it is not
    3790    limited to textual documents.
    3791 </t>
    3792 </section>
    3793 
    3794 <section title="Content-Location" anchor="header.content-location">
    3795   <iref primary="true" item="Content-Location header field" x:for-anchor=""/>
    3796   <iref primary="true" item="Header Fields" subitem="Content-Location" x:for-anchor=""/>
    3797   <x:anchor-alias value="Content-Location"/>
    3798 <t>
    3799    The "Content-Location" header field supplies a URI that can be used
    3800    as a specific identifier for the representation in this message.
    3801    In other words, if one were to perform a GET on this URI at the time
    3802    of this message's generation, then a 200 response would contain the
    3803    same representation that is enclosed as payload in this message.
    3804 </t>
    3805 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Location"/>
    3806   <x:ref>Content-Location</x:ref> = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
    3807 </artwork></figure>
    3808 <t>
    3809    The Content-Location value is not a replacement for the effective
    3810    Request URI (&effective-request-uri;).  It is representation metadata.
    3811    It has the same syntax and semantics as the header field of the same name
    3812    defined for MIME body parts in <xref target="RFC2557" x:fmt="of" x:sec="4"/>.
    3813    However, its appearance in an HTTP message has some special implications
    3814    for HTTP recipients.
    3815 </t>
    3816 <t>
    3817    If Content-Location is included in a response message and its value
    3818    is the same as the effective request URI, then the response payload
    3819    &SHOULD; be considered a current representation of that resource.
    3820    For a GET or HEAD request, this is the same as the default semantics
    3821    when no Content-Location is provided by the server.  For a state-changing
    3822    request like PUT or POST, it implies that the server's response contains
    3823    the new representation of that resource, thereby distinguishing it from
    3824    representations that might only report about the action (e.g., "It worked!").
    3825    This allows authoring applications to update their local copies without
    3826    the need for a subsequent GET request.
    3827 </t>
    3828 <t>
    3829    If Content-Location is included in a response message and its value
    3830    differs from the effective request URI, then the origin server is
    3831    informing recipients that this representation has its own, presumably
    3832    more specific, identifier.  For a GET or HEAD request, this is an
    3833    indication that the effective request URI identifies a resource that
    3834    is subject to content negotiation and the selected representation for
    3835    this response can also be found at the identified URI.  For other
    3836    methods, such a Content-Location indicates that this representation
    3837    contains a report on the action's status and the same report is
    3838    available (for future access with GET) at the given URI.  For
    3839    example, a purchase transaction made via a POST request might
    3840    include a receipt document as the payload of the 200 response;
    3841    the Content-Location value provides an identifier for retrieving
    3842    a copy of that same receipt in the future.
    3843 </t>
    3844 <t>
    3845    If Content-Location is included in a request message, then it &MAY;
    3846    be interpreted by the origin server as an indication of where the
    3847    user agent originally obtained the content of the enclosed
    3848    representation (prior to any subsequent modification of the content
    3849    by that user agent).  In other words, the user agent is providing
    3850    the same representation metadata that it received with the original
    3851    representation.  However, such interpretation &MUST-NOT; be used to
    3852    alter the semantics of the method requested by the client.  For
    3853    example, if a client makes a PUT request on a negotiated resource
    3854    and the origin server accepts that PUT (without redirection), then the
    3855    new set of values for that resource is expected to be consistent with
    3856    the one representation supplied in that PUT; the Content-Location
    3857    cannot be used as a form of reverse content selection that
    3858    identifies only one of the negotiated representations to be updated.
    3859    If the user agent had wanted the latter semantics, it would have applied
    3860    the PUT directly to the Content-Location URI.
    3861 </t>
    3862 <t>
    3863    A Content-Location field received in a request message is transitory
    3864    information that &SHOULD-NOT; be saved with other representation
    3865    metadata for use in later responses.  The Content-Location's value
    3866    might be saved for use in other contexts, such as within source links
    3867    or other metadata.
    3868 </t>
    3869 <t>
    3870    A cache cannot assume that a representation with a Content-Location
    3871    different from the URI used to retrieve it can be used to respond to
    3872    later requests on that Content-Location URI.
    3873 </t>
    3874 <t>
    3875    If the Content-Location value is a partial URI, the partial URI is
    3876    interpreted relative to the effective request URI.
    3877 </t>
    3878 </section>
    3879 
    3880 <section title="Content-Type" anchor="header.content-type">
    3881   <iref primary="true" item="Content-Type header field" x:for-anchor=""/>
    3882   <iref primary="true" item="Header Fields" subitem="Content-Type" x:for-anchor=""/>
    3883   <x:anchor-alias value="Content-Type"/>
    3884 <t>
    3885    The "Content-Type" header field indicates the media type of the
    3886    representation. In the case of responses to the HEAD method, the media type is
    3887    that which would have been sent had the request been a GET.
    3888 </t>
    3889 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Content-Type"/>
    3890   <x:ref>Content-Type</x:ref> = <x:ref>media-type</x:ref>
    3891 </artwork></figure>
    3892 <t>
    3893    Media types are defined in <xref target="media.types"/>. An example of the field is
    3894 </t>
    3895 <figure><artwork type="example">
    3896   Content-Type: text/html; charset=ISO-8859-4
    3897 </artwork></figure>
    3898 <t>
    3899    Further discussion of Content-Type is provided in <xref target="representation.data"/>.
    3900 </t>
    39013901</section>
    39023902

  • draft-ietf-httpbis/experiment/p4-conditional.html

    r1631 r1633  
    896896      </div>
    897897      <h3 id="rfc.section.2.3.3"><a href="#rfc.section.2.3.3">2.3.3</a>&nbsp;<a id="example.entity.tag.vs.conneg" href="#example.entity.tag.vs.conneg">Example: Entity-tags varying on Content-Negotiated Resources</a></h3>
    898       <p id="rfc.section.2.3.3.p.1">Consider a resource that is subject to content negotiation (<a href="p2-semantics.html#content.negotiation" title="Content Negotiation">Section 8</a> of <a href="#Part2" id="rfc.xref.Part2.3"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), and where the representations returned upon a GET request vary based on the Accept-Encoding request header field (<a href="p2-semantics.html#header.accept-encoding" title="Accept-Encoding">Section 9.13</a> of <a href="#Part2" id="rfc.xref.Part2.4"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>):
     898      <p id="rfc.section.2.3.3.p.1">Consider a resource that is subject to content negotiation (<a href="p2-semantics.html#content.negotiation" title="Content Negotiation">Section 8</a> of <a href="#Part2" id="rfc.xref.Part2.3"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>), and where the representations returned upon a GET request vary based on the Accept-Encoding request header field (<a href="p2-semantics.html#header.accept-encoding" title="Accept-Encoding">Section 9.3</a> of <a href="#Part2" id="rfc.xref.Part2.4"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>):
    899899      </p>
    900900      <div id="rfc.figure.u.6"></div>
    … …  
    11231123         as if it were the payload of a 200 response. The 304 response <em class="bcp14">MUST NOT</em> contain a message-body, and thus is always terminated by the first empty line after the header fields.
    11241124      </p>
    1125       <p id="rfc.section.4.1.p.2">A 304 response <em class="bcp14">MUST</em> include a Date header field (<a href="p2-semantics.html#header.date" title="Date">Section 9.2</a> of <a href="#Part2" id="rfc.xref.Part2.5"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) unless the origin server does not have a clock that can provide a reasonable approximation of the current time. If a 200
     1125      <p id="rfc.section.4.1.p.2">A 304 response <em class="bcp14">MUST</em> include a Date header field (<a href="p2-semantics.html#header.date" title="Date">Section 9.10</a> of <a href="#Part2" id="rfc.xref.Part2.5"><cite title="HTTP/1.1, part 2: Message Semantics">[Part2]</cite></a>) unless the origin server does not have a clock that can provide a reasonable approximation of the current time. If a 200
    11261126         response to the same request would have included any of the header fields Cache-Control, Content-Location, ETag, Expires,
    11271127         or Vary, then those same header fields <em class="bcp14">MUST</em> be sent in a 304 response.
    … …  
    13181318      <div id="rfc.figure.u.17"></div> <pre class="inline"><a href="#header.etag" class="smpl">ETag</a> = entity-tag
    13191319
    1320 <a href="#notation" class="smpl">HTTP-date</a> = &lt;HTTP-date, defined in [Part2], Section 6.1&gt;
     1320<a href="#notation" class="smpl">HTTP-date</a> = &lt;HTTP-date, defined in [Part2], Section 5.1&gt;
    13211321
    13221322<a href="#header.if-match" class="smpl">If-Match</a> = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS
    … …  
    14261426                        <li><em>Section 5.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.2">1.2</a></li>
    14271427                        <li><em>Section 8</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.3">2.3.3</a></li>
    1428                         <li><em>Section 9.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.5">4.1</a></li>
    1429                         <li><em>Section 9.13</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.4">2.3.3</a></li>
     1428                        <li><em>Section 9.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.4">2.3.3</a></li>
     1429                        <li><em>Section 9.10</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.5">4.1</a></li>
    14301430                     </ul>
    14311431                  </li>

  • draft-ietf-httpbis/experiment/p4-conditional.xml

    r1630 r1633  
    13681368<x:ref>ETag</x:ref> = entity-tag
    13691369
    1370 <x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part2], Section 6.1&gt;
     1370<x:ref>HTTP-date</x:ref> = &lt;HTTP-date, defined in [Part2], Section 5.1&gt;
    13711371
    13721372<x:ref>If-Match</x:ref> = "*" / ( *( "," OWS ) entity-tag *( OWS "," [ OWS
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