Changeset 2106


Ignore:
Timestamp:
Jan 10, 2013, 10:03:59 PM (7 years ago)
Author:
fielding@…
Message:

(editorial) move Vary to the control data section; no content changes

Location:
draft-ietf-httpbis/latest
Files:
2 edited

Legend:

Unmodified
Added
Removed
  • draft-ietf-httpbis/latest/p2-semantics.html

    r2105 r2106  
    725725                     <li><a href="#rfc.section.7.1.2">7.1.2</a>&nbsp;&nbsp;&nbsp;<a href="#header.location">Location</a></li>
    726726                     <li><a href="#rfc.section.7.1.3">7.1.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.retry-after">Retry-After</a></li>
     727                     <li><a href="#rfc.section.7.1.4">7.1.4</a>&nbsp;&nbsp;&nbsp;<a href="#header.vary">Vary</a></li>
    727728                  </ul>
    728729               </li>
    729                <li><a href="#rfc.section.7.2">7.2</a>&nbsp;&nbsp;&nbsp;<a href="#selected.representation">Selected Representation Header Fields</a><ul>
    730                      <li><a href="#rfc.section.7.2.1">7.2.1</a>&nbsp;&nbsp;&nbsp;<a href="#header.vary">Vary</a></li>
    731                   </ul>
    732                </li>
     730               <li><a href="#rfc.section.7.2">7.2</a>&nbsp;&nbsp;&nbsp;<a href="#selected.representation">Selected Representation Header Fields</a></li>
    733731               <li><a href="#rfc.section.7.3">7.3</a>&nbsp;&nbsp;&nbsp;<a href="#response.auth">Authentication Challenges</a></li>
    734732               <li><a href="#rfc.section.7.4">7.4</a>&nbsp;&nbsp;&nbsp;<a href="#response.context">Response Context</a><ul>
     
    12241222         the user agent's preferences is better than sending a <a href="#status.406" class="smpl">406 (Not Acceptable)</a> response.
    12251223      </p>
    1226       <p id="rfc.section.3.4.1.p.5">An origin server <em class="bcp14">MAY</em> generate a <a href="#header.vary" class="smpl">Vary</a> header field (<a href="#header.vary" id="rfc.xref.header.vary.1" title="Vary">Section&nbsp;7.2.1</a>) in responses that are subject to proactive negotiation to indicate what parameters of request information might be used
     1224      <p id="rfc.section.3.4.1.p.5">An origin server <em class="bcp14">MAY</em> generate a <a href="#header.vary" class="smpl">Vary</a> header field (<a href="#header.vary" id="rfc.xref.header.vary.1" title="Vary">Section&nbsp;7.1.4</a>) in responses that are subject to proactive negotiation to indicate what parameters of request information might be used
    12271225         in its selection algorithm, thereby providing a means for recipients to determine the reusability of that same response for
    12281226         user agents with differing request information.
     
    24472445         primary resource created by the request is identified by either a <a href="#header.location" class="smpl">Location</a> header field in the response or, if no <a href="#header.location" class="smpl">Location</a> field is received, by the effective request URI.
    24482446      </p>
    2449       <p id="rfc.section.6.3.2.p.2">The 201 response payload typically describes and links to the resource(s) created. See <a href="#selected.representation" title="Selected Representation Header Fields">Section&nbsp;7.2</a> for discussion of the meaning and purpose of selected representation header fields, such as <a href="p4-conditional.html#header.etag" class="smpl">ETag</a> and Last-Modified, in a 201 response.
     2447      <p id="rfc.section.6.3.2.p.2">The 201 response payload typically describes and links to the resource(s) created. See <a href="#selected.representation" title="Selected Representation Header Fields">Section&nbsp;7.2</a> for discussion of the meaning and purpose of selected representation header fields, such as <a href="p4-conditional.html#header.etag" class="smpl">ETag</a> and <a href="p4-conditional.html#header.last-modified" class="smpl">Last-Modified</a>, in a 201 response.
    24502448      </p>
    24512449      <div id="rfc.iref.72"></div>
     
    28242822                  <td class="left">Retry-After</td>
    28252823                  <td class="left"><a href="#header.retry-after" id="rfc.xref.header.retry-after.2" title="Retry-After">Section&nbsp;7.1.3</a></td>
     2824               </tr>
     2825               <tr>
     2826                  <td class="left">Vary</td>
     2827                  <td class="left"><a href="#header.vary" id="rfc.xref.header.vary.2" title="Vary">Section&nbsp;7.1.4</a></td>
    28262828               </tr>
    28272829               <tr>
     
    29972999  Retry-After: 120
    29983000</pre><p id="rfc.section.7.1.3.p.8">In the latter example, the delay is 2 minutes.</p>
     3001      <div id="rfc.iref.v.1"></div>
     3002      <h3 id="rfc.section.7.1.4"><a href="#rfc.section.7.1.4">7.1.4</a>&nbsp;<a id="header.vary" href="#header.vary">Vary</a></h3>
     3003      <p id="rfc.section.7.1.4.p.1">The "Vary" header field describes what parts of a request message, aside from the method and request target, might influence
     3004         the origin server's process for selecting and representing the response. The value consists of either a single asterisk ("*")
     3005         or a list of header field names (case-insensitive).
     3006      </p>
     3007      <div id="rfc.figure.u.57"></div><pre class="inline"><span id="rfc.iref.g.59"></span>  <a href="#header.vary" class="smpl">Vary</a> = "*" / 1#<a href="#imported.abnf" class="smpl">field-name</a>
     3008</pre><p id="rfc.section.7.1.4.p.3">A Vary field value of "*" signals that anything about the request might play a role in selecting the response representation,
     3009         possibly including elements outside the message syntax (e.g., the client's network address), and thus a recipient will not
     3010         be able to determine whether this response is appropriate for a later request without forwarding the request to the origin
     3011         server. A proxy <em class="bcp14">MUST NOT</em> generate a Vary field with a "*" value.
     3012      </p>
     3013      <p id="rfc.section.7.1.4.p.4">A Vary field value consisting of a comma-separated list of names indicates that the named request header fields, known as
     3014         the selecting header fields, might have a role in selecting the representation. The potential selecting header fields are
     3015         not limited to those defined by this specification.
     3016      </p>
     3017      <div id="rfc.figure.u.58"></div>
     3018      <p>For example, a response that contains</p><pre class="text">  Vary: accept-encoding, accept-language
     3019</pre><p>indicates that the origin server might have used the request's <a href="#header.accept-encoding" class="smpl">Accept-Encoding</a> and <a href="#header.accept-language" class="smpl">Accept-Language</a> fields (or lack thereof) as determining factors while choosing this <a href="#selected.representation" class="smpl">selected representation</a>.
     3020      </p>
     3021      <p id="rfc.section.7.1.4.p.6">An origin server might send Vary with a list of fields for two purposes: </p>
     3022      <ol>
     3023         <li>
     3024            <p>To inform cache recipients that they <em class="bcp14">MUST NOT</em> use this response to satisfy a later request unless the later request has the same values for the listed fields as the original
     3025               request (<a href="p6-cache.html#caching.negotiated.responses" title="Using Negotiated Responses">Section 4.3</a> of <a href="#Part6" id="rfc.xref.Part6.19"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Caching">[Part6]</cite></a>). In other words, Vary expands the cache key required to match a new request to the stored cache entry.
     3026            </p>
     3027         </li>
     3028         <li>
     3029            <p>To inform user agent recipients that this response is subject to content negotiation (<a href="#request.conneg" title="Content Negotiation">Section&nbsp;5.3</a>) and that a different representation might be sent in a subsequent request if additional parameters are provided in the listed
     3030               header fields (<a href="#proactive.negotiation" class="smpl">proactive negotiation</a>).
     3031            </p>
     3032         </li>
     3033      </ol>
     3034      <p id="rfc.section.7.1.4.p.7">An origin server <em class="bcp14">SHOULD</em> send a Vary header field when its algorithm for selecting a representation varies based on aspects of the request message
     3035         other than the method and request target, unless the variance cannot be crossed or the origin server has been deliberately
     3036         configured to prevent cache transparency. For example, there is no need to send the Authorization field name (<a href="p7-auth.html#header.authorization" title="Authorization">Section 4.1</a> of <a href="#Part7" id="rfc.xref.Part7.7"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Authentication">[Part7]</cite></a>) in Vary because reuse across users is constrained by the field definition. Likewise, Cache-Control directives (<a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 7.2</a> of <a href="#Part6" id="rfc.xref.Part6.20"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Caching">[Part6]</cite></a>) might be used to supplant the need for Vary, particularly when the variance is considered less significant than the performance
     3037         cost of Vary's impact on caching.
     3038      </p>
    29993039      <div id="rfc.iref.s.7"></div>
    30003040      <h2 id="rfc.section.7.2"><a href="#rfc.section.7.2">7.2</a>&nbsp;<a id="selected.representation" href="#selected.representation">Selected Representation Header Fields</a></h2>
     
    30243064                  <td class="left"><a href="p4-conditional.html#header.last-modified" title="Last-Modified">Section 2.2</a> of <a href="#Part4" id="rfc.xref.Part4.12"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests">[Part4]</cite></a></td>
    30253065               </tr>
    3026                <tr>
    3027                   <td class="left">Vary</td>
    3028                   <td class="left"><a href="#header.vary" id="rfc.xref.header.vary.2" title="Vary">Section&nbsp;7.2.1</a></td>
    3029                </tr>
    30303066            </tbody>
    30313067         </table>
    30323068      </div>
    3033       <div id="rfc.iref.v.1"></div>
    3034       <h3 id="rfc.section.7.2.1"><a href="#rfc.section.7.2.1">7.2.1</a>&nbsp;<a id="header.vary" href="#header.vary">Vary</a></h3>
    3035       <p id="rfc.section.7.2.1.p.1">The "Vary" header field describes what parts of a request message, aside from the method and request target, might influence
    3036          the origin server's process for selecting and representing the response. The value consists of either a single asterisk ("*")
    3037          or a list of header field names (case-insensitive).
    3038       </p>
    3039       <div id="rfc.figure.u.57"></div><pre class="inline"><span id="rfc.iref.g.59"></span>  <a href="#header.vary" class="smpl">Vary</a> = "*" / 1#<a href="#imported.abnf" class="smpl">field-name</a>
    3040 </pre><p id="rfc.section.7.2.1.p.3">A Vary field value of "*" signals that anything about the request might play a role in selecting the response representation,
    3041          possibly including elements outside the message syntax (e.g., the client's network address), and thus a recipient will not
    3042          be able to determine whether this response is appropriate for a later request without forwarding the request to the origin
    3043          server. A proxy <em class="bcp14">MUST NOT</em> generate a Vary field with a "*" value.
    3044       </p>
    3045       <p id="rfc.section.7.2.1.p.4">A Vary field value consisting of a comma-separated list of names indicates that the named request header fields, known as
    3046          the selecting header fields, might have a role in selecting the representation. The potential selecting header fields are
    3047          not limited to those defined by this specification.
    3048       </p>
    3049       <div id="rfc.figure.u.58"></div>
    3050       <p>For example, a response that contains</p><pre class="text">  Vary: accept-encoding, accept-language
    3051 </pre><p>indicates that the origin server might have used the request's <a href="#header.accept-encoding" class="smpl">Accept-Encoding</a> and <a href="#header.accept-language" class="smpl">Accept-Language</a> fields (or lack thereof) as determining factors while choosing this <a href="#selected.representation" class="smpl">selected representation</a>.
    3052       </p>
    3053       <p id="rfc.section.7.2.1.p.6">An origin server might send Vary with a list of fields for two purposes: </p>
    3054       <ol>
    3055          <li>
    3056             <p>To inform cache recipients that they <em class="bcp14">MUST NOT</em> use this response to satisfy a later request unless the later request has the same values for the listed fields as the original
    3057                request (<a href="p6-cache.html#caching.negotiated.responses" title="Using Negotiated Responses">Section 4.3</a> of <a href="#Part6" id="rfc.xref.Part6.19"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Caching">[Part6]</cite></a>). In other words, Vary expands the cache key required to match a new request to the stored cache entry.
    3058             </p>
    3059          </li>
    3060          <li>
    3061             <p>To inform user agent recipients that this response is subject to content negotiation (<a href="#request.conneg" title="Content Negotiation">Section&nbsp;5.3</a>) and that a different representation might be sent in a subsequent request if additional parameters are provided in the listed
    3062                header fields (<a href="#proactive.negotiation" class="smpl">proactive negotiation</a>).
    3063             </p>
    3064          </li>
    3065       </ol>
    3066       <p id="rfc.section.7.2.1.p.7">An origin server <em class="bcp14">SHOULD</em> send a Vary header field when its algorithm for selecting a representation varies based on aspects of the request message
    3067          other than the method and request target, unless the variance cannot be crossed or the origin server has been deliberately
    3068          configured to prevent cache transparency. For example, there is no need to send the Authorization field name (<a href="p7-auth.html#header.authorization" title="Authorization">Section 4.1</a> of <a href="#Part7" id="rfc.xref.Part7.7"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Authentication">[Part7]</cite></a>) in Vary because reuse across users is constrained by the field definition. Likewise, Cache-Control directives (<a href="p6-cache.html#header.cache-control" title="Cache-Control">Section 7.2</a> of <a href="#Part6" id="rfc.xref.Part6.20"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Caching">[Part6]</cite></a>) might be used to supplant the need for Vary, particularly when the variance is considered less significant than the performance
    3069          cost of Vary's impact on caching.
    3070       </p>
    30713069      <h2 id="rfc.section.7.3"><a href="#rfc.section.7.3">7.3</a>&nbsp;<a id="response.auth" href="#response.auth">Authentication Challenges</a></h2>
    30723070      <p id="rfc.section.7.3.p.1">Authentication challenges indicate what mechanisms are available for the client to provide authentication credentials in future
     
    37403738                  <td class="left">http</td>
    37413739                  <td class="left">standard</td>
    3742                   <td class="left"> <a href="#header.vary" id="rfc.xref.header.vary.3" title="Vary">Section&nbsp;7.2.1</a>
     3740                  <td class="left"> <a href="#header.vary" id="rfc.xref.header.vary.3" title="Vary">Section&nbsp;7.1.4</a>
    37433741                  </td>
    37443742               </tr>
     
    45584556                        <li><tt>User-Agent</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.36"><b>5.5.3</b></a></li>
    45594557                        <li><tt>value</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.6"><b>3.1.1.1</b></a></li>
    4560                         <li><tt>Vary</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.59"><b>7.2.1</b></a></li>
     4558                        <li><tt>Vary</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.59"><b>7.1.4</b></a></li>
    45614559                        <li><tt>weight</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.23"><b>5.3.1</b></a></li>
    45624560                        <li><tt>year</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.50"><b>7.1.1.1</b></a></li>
     
    46414639                     </ul>
    46424640                  </li>
    4643                   <li><em>Part6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">4.2.3</a>, <a href="#rfc.xref.Part6.2">4.3.1</a>, <a href="#rfc.xref.Part6.3">4.3.2</a>, <a href="#rfc.xref.Part6.4">4.3.2</a>, <a href="#rfc.xref.Part6.5">4.3.3</a>, <a href="#rfc.xref.Part6.6">4.3.4</a>, <a href="#rfc.xref.Part6.7">4.3.5</a>, <a href="#rfc.xref.Part6.8">5.1</a>, <a href="#rfc.xref.Part6.9">5.1</a>, <a href="#rfc.xref.Part6.10">6.3.1</a>, <a href="#rfc.xref.Part6.11">6.3.4</a>, <a href="#rfc.xref.Part6.12">6.4.1</a>, <a href="#rfc.xref.Part6.13">6.4.2</a>, <a href="#rfc.xref.Part6.14">6.5.9</a>, <a href="#rfc.xref.Part6.15">7.1</a>, <a href="#rfc.xref.Part6.16">7.1</a>, <a href="#rfc.xref.Part6.17">7.1</a>, <a href="#rfc.xref.Part6.18">7.1</a>, <a href="#rfc.xref.Part6.19">7.2.1</a>, <a href="#rfc.xref.Part6.20">7.2.1</a>, <a href="#rfc.xref.Part6.21">8.2.2</a>, <a href="#rfc.xref.Part6.22">8.3.1</a>, <a href="#Part6"><b>11.1</b></a><ul>
     4641                  <li><em>Part6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">4.2.3</a>, <a href="#rfc.xref.Part6.2">4.3.1</a>, <a href="#rfc.xref.Part6.3">4.3.2</a>, <a href="#rfc.xref.Part6.4">4.3.2</a>, <a href="#rfc.xref.Part6.5">4.3.3</a>, <a href="#rfc.xref.Part6.6">4.3.4</a>, <a href="#rfc.xref.Part6.7">4.3.5</a>, <a href="#rfc.xref.Part6.8">5.1</a>, <a href="#rfc.xref.Part6.9">5.1</a>, <a href="#rfc.xref.Part6.10">6.3.1</a>, <a href="#rfc.xref.Part6.11">6.3.4</a>, <a href="#rfc.xref.Part6.12">6.4.1</a>, <a href="#rfc.xref.Part6.13">6.4.2</a>, <a href="#rfc.xref.Part6.14">6.5.9</a>, <a href="#rfc.xref.Part6.15">7.1</a>, <a href="#rfc.xref.Part6.16">7.1</a>, <a href="#rfc.xref.Part6.17">7.1</a>, <a href="#rfc.xref.Part6.18">7.1</a>, <a href="#rfc.xref.Part6.19">7.1.4</a>, <a href="#rfc.xref.Part6.20">7.1.4</a>, <a href="#rfc.xref.Part6.21">8.2.2</a>, <a href="#rfc.xref.Part6.22">8.3.1</a>, <a href="#Part6"><b>11.1</b></a><ul>
    46444642                        <li><em>Section 4.1.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.5">4.3.3</a></li>
    46454643                        <li><em>Section 4.1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.10">6.3.1</a>, <a href="#rfc.xref.Part6.12">6.4.1</a>, <a href="#rfc.xref.Part6.13">6.4.2</a>, <a href="#rfc.xref.Part6.14">6.5.9</a></li>
    4646                         <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.19">7.2.1</a></li>
     4644                        <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.19">7.1.4</a></li>
    46474645                        <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.4">4.3.2</a></li>
    46484646                        <li><em>Section 6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.6">4.3.4</a>, <a href="#rfc.xref.Part6.7">4.3.5</a></li>
    46494647                        <li><em>Section 7.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.15">7.1</a></li>
    4650                         <li><em>Section 7.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.2">4.3.1</a>, <a href="#rfc.xref.Part6.3">4.3.2</a>, <a href="#rfc.xref.Part6.8">5.1</a>, <a href="#rfc.xref.Part6.16">7.1</a>, <a href="#rfc.xref.Part6.20">7.2.1</a></li>
     4648                        <li><em>Section 7.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.2">4.3.1</a>, <a href="#rfc.xref.Part6.3">4.3.2</a>, <a href="#rfc.xref.Part6.8">5.1</a>, <a href="#rfc.xref.Part6.16">7.1</a>, <a href="#rfc.xref.Part6.20">7.1.4</a></li>
    46514649                        <li><em>Section 7.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.17">7.1</a></li>
    46524650                        <li><em>Section 7.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.9">5.1</a></li>
     
    46544652                     </ul>
    46554653                  </li>
    4656                   <li><em>Part7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.1">4.3.8</a>, <a href="#rfc.xref.Part7.2">5.4</a>, <a href="#rfc.xref.Part7.3">5.4</a>, <a href="#rfc.xref.Part7.4">6.1</a>, <a href="#rfc.xref.Part7.5">6.1</a>, <a href="#rfc.xref.Part7.6">6.1</a>, <a href="#rfc.xref.Part7.7">7.2.1</a>, <a href="#rfc.xref.Part7.8">7.3</a>, <a href="#rfc.xref.Part7.9">7.3</a>, <a href="#Part7"><b>11.1</b></a><ul>
     4654                  <li><em>Part7</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.1">4.3.8</a>, <a href="#rfc.xref.Part7.2">5.4</a>, <a href="#rfc.xref.Part7.3">5.4</a>, <a href="#rfc.xref.Part7.4">6.1</a>, <a href="#rfc.xref.Part7.5">6.1</a>, <a href="#rfc.xref.Part7.6">6.1</a>, <a href="#rfc.xref.Part7.7">7.1.4</a>, <a href="#rfc.xref.Part7.8">7.3</a>, <a href="#rfc.xref.Part7.9">7.3</a>, <a href="#Part7"><b>11.1</b></a><ul>
    46574655                        <li><em>Section 3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.4">6.1</a></li>
    46584656                        <li><em>Section 3.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.5">6.1</a></li>
    46594657                        <li><em>Section 3.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.6">6.1</a></li>
    4660                         <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.2">5.4</a>, <a href="#rfc.xref.Part7.7">7.2.1</a></li>
     4658                        <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.2">5.4</a>, <a href="#rfc.xref.Part7.7">7.1.4</a></li>
    46614659                        <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.9">7.3</a></li>
    46624660                        <li><em>Section 4.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part7.3">5.4</a></li>
     
    47754773            </li>
    47764774            <li><a id="rfc.index.V" href="#rfc.index.V"><b>V</b></a><ul>
    4777                   <li>Vary header field&nbsp;&nbsp;<a href="#rfc.xref.header.vary.1">3.4.1</a>, <a href="#rfc.xref.header.vary.2">7.2</a>, <a href="#rfc.iref.v.1"><b>7.2.1</b></a>, <a href="#rfc.xref.header.vary.3">8.3.2</a></li>
     4775                  <li>Vary header field&nbsp;&nbsp;<a href="#rfc.xref.header.vary.1">3.4.1</a>, <a href="#rfc.xref.header.vary.2">7.1</a>, <a href="#rfc.iref.v.1"><b>7.1.4</b></a>, <a href="#rfc.xref.header.vary.3">8.3.2</a></li>
    47784776               </ul>
    47794777            </li>
  • draft-ietf-httpbis/latest/p2-semantics.xml

    r2105 r2106  
    35473547  <c>Location</c> <c><xref target="header.location"/></c>
    35483548  <c>Retry-After</c> <c><xref target="header.retry-after"/></c>
     3549  <c>Vary</c> <c><xref target="header.vary"/></c>
    35493550  <c>Warning</c> <c>&header-warning;</c>
    35503551</texttable>
     
    38653866</t>
    38663867</section>
    3867 </section>
    3868 
    3869 <section title="Selected Representation Header Fields" anchor="selected.representation">
    3870    <iref primary="true" item="selected representation"/>
    3871    <x:anchor-alias value="selected representation"/>
    3872 <t>
    3873    We use the term "<x:dfn>selected representation</x:dfn>" to refer to the
    3874    representation of the <x:ref>target resource</x:ref> in a
    3875    <x:ref>200 (OK)</x:ref> response to <x:ref>GET</x:ref>, or the
    3876    representation that would have been selected in a successful response if
    3877    the request had used the method <x:ref>GET</x:ref> and excluded any
    3878    conditional request header fields.
    3879 </t>
    3880 <t>
    3881    The following header fields define metadata about the selected
    3882    representation at the conclusion of handling the request. In other words,
    3883    for a successful response to a state-changing method, these fields describe
    3884    the new representation that has replaced the prior selected representation.
    3885    For example, an ETag header field in a 201 response communicates the
    3886    entity-tag of the newly created resource's representation, so that it can
    3887    be used in later conditional requests to prevent the "lost update"
    3888    problem <xref target="Part4"/>.
    3889 </t>
    3890 <texttable align="left">
    3891   <ttcol>Header Field Name</ttcol>
    3892   <ttcol>Defined in...</ttcol>
    3893 
    3894   <c>ETag</c> <c>&header-etag;</c>
    3895   <c>Last-Modified</c> <c>&header-last-modified;</c>
    3896   <c>Vary</c> <c><xref target="header.vary"/></c>
    3897 </texttable>
    38983868
    38993869<section anchor="header.vary" title="Vary">
     
    39673937</t>
    39683938</section>
     3939</section>
     3940
     3941<section title="Selected Representation Header Fields" anchor="selected.representation">
     3942   <iref primary="true" item="selected representation"/>
     3943   <x:anchor-alias value="selected representation"/>
     3944<t>
     3945   We use the term "<x:dfn>selected representation</x:dfn>" to refer to the
     3946   representation of the <x:ref>target resource</x:ref> in a
     3947   <x:ref>200 (OK)</x:ref> response to <x:ref>GET</x:ref>, or the
     3948   representation that would have been selected in a successful response if
     3949   the request had used the method <x:ref>GET</x:ref> and excluded any
     3950   conditional request header fields.
     3951</t>
     3952<t>
     3953   The following header fields define metadata about the selected
     3954   representation at the conclusion of handling the request. In other words,
     3955   for a successful response to a state-changing method, these fields describe
     3956   the new representation that has replaced the prior selected representation.
     3957   For example, an ETag header field in a 201 response communicates the
     3958   entity-tag of the newly created resource's representation, so that it can
     3959   be used in later conditional requests to prevent the "lost update"
     3960   problem <xref target="Part4"/>.
     3961</t>
     3962<texttable align="left">
     3963  <ttcol>Header Field Name</ttcol>
     3964  <ttcol>Defined in...</ttcol>
     3965
     3966  <c>ETag</c> <c>&header-etag;</c>
     3967  <c>Last-Modified</c> <c>&header-last-modified;</c>
     3968</texttable>
     3969
    39693970</section>
    39703971
     
    49654966    <x:defines>If-None-Match</x:defines>
    49664967    <x:defines>If-Unmodified-Since</x:defines>
     4968    <x:defines>Last-Modified</x:defines>
    49674969  </x:source>
    49684970</reference>
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