Ignore:
Timestamp:
24/08/11 01:30:58 (10 years ago)
Author:
fielding@…
Message:

Remove the "identity" content-coding -- it is just a token used
as a synonym for no encoding and calling it anything else makes
all the other requirements a silly mess.

Fix the English grammatical errors in recent changes to the
Accept* header fields.

File:
1 edited

Legend:

Unmodified
Added
Removed

  • draft-ietf-httpbis/latest/p3-payload.html

    r1405 r1406  
    732732         </li>
    733733      </ul>
    734       <p id="rfc.section.2.2.p.7">identity<span id="rfc.iref.i.1"></span><span id="rfc.iref.c.6"></span> 
    735       </p>
    736       <ul class="empty">
    737          <li>The default (identity) encoding; the use of no transformation whatsoever. This content-coding is used only in the Accept-Encoding
    738             header field, and <em class="bcp14">SHOULD NOT</em> be used in the Content-Encoding header field.
    739          </li>
    740       </ul>
    741734      <h3 id="rfc.section.2.2.1"><a href="#rfc.section.2.2.1">2.2.1</a>&nbsp;<a id="content.coding.registry" href="#content.coding.registry">Content Coding Registry</a></h3>
    742735      <p id="rfc.section.2.2.1.p.1">The HTTP Content Coding Registry defines the name space for the content coding names.</p>
    … …  
    10611054         quality".
    10621055      </p>
    1063       <p id="rfc.section.6.1.p.9">If no Accept header field is present, then it is assumed that the client accepts all media types. If an Accept header field
    1064          is present in a request, but the server cannot send a response which is acceptable, then the server can either send a response
    1065          in another format, or a 406 (Not Acceptable) response.
     1056      <p id="rfc.section.6.1.p.9">A request without any Accept header field implies that the user agent will accept any media type in response. If an Accept
     1057         header field is present in a request and none of the available representations for the response have a media type that is
     1058         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
     1059         the response as if it is not subject to content negotiation.
    10661060      </p>
    10671061      <p id="rfc.section.6.1.p.10">A more elaborate example is</p>
    … …  
    11441138         mentioned get a quality value of 0.
    11451139      </p>
    1146       <p id="rfc.section.6.2.p.6">If no Accept-Charset header field is present, the default is that any character encoding is acceptable. If an Accept-Charset
    1147          header field is present in a request, but the server cannot send a response which is acceptable, then the server can either
    1148          use another character encoding, or send a 406 (Not Acceptable) response.
     1140      <p id="rfc.section.6.2.p.6">A request without any Accept-Charset header field implies that the user agent will accept any character encoding in response.
     1141         If an Accept-Charset header field is present in a request and none of the available representations for the response have
     1142         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
     1143         field by treating the response as if it is not subject to content negotiation.
    11491144      </p>
    11501145      <div id="rfc.iref.a.3"></div>
    11511146      <div id="rfc.iref.h.3"></div>
    11521147      <h2 id="rfc.section.6.3"><a href="#rfc.section.6.3">6.3</a>&nbsp;<a id="header.accept-encoding" href="#header.accept-encoding">Accept-Encoding</a></h2>
    1153       <p id="rfc.section.6.3.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;2.2</a>) are acceptable in the response.
     1148      <p id="rfc.section.6.3.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;2.2</a>) are acceptable in the response. An "identity" token is used as a synonym for "no encoding" in order to communicate when
     1149         no encoding is preferred.
    11541150      </p>
    11551151      <div id="rfc.figure.u.17"></div><pre class="inline"><span id="rfc.iref.g.16"></span><span id="rfc.iref.g.17"></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> ] )
    1156   <a href="#header.accept-encoding" class="smpl">codings</a>          = ( <a href="#content.codings" class="smpl">content-coding</a> / "*" )
     1152  <a href="#header.accept-encoding" class="smpl">codings</a>          = <a href="#content.codings" class="smpl">content-coding</a>
     1153                                  / "identity"
     1154                                  / "*"
    11571155</pre><p id="rfc.section.6.3.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.
    11581156      </p>
    1159       <p id="rfc.section.6.3.p.4">Examples of its use are:</p>
     1157      <p id="rfc.section.6.3.p.4">For example,</p>
    11601158      <div id="rfc.figure.u.18"></div><pre class="text">  Accept-Encoding: compress, gzip
    11611159  Accept-Encoding:
    … …  
    11631161  Accept-Encoding: compress;q=0.5, gzip;q=1.0
    11641162  Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
    1165 </pre><p id="rfc.section.6.3.p.6">A server tests whether a content-coding is acceptable, according to an Accept-Encoding field, using these rules: </p>
     1163</pre><p id="rfc.section.6.3.p.6">A server tests whether a content-coding for a given representation is acceptable, according to an Accept-Encoding field, using
     1164         these rules:
     1165      </p>
    11661166      <ol>
    1167          <li>If the content-coding is one of the content-codings listed in the Accept-Encoding field, then it is acceptable, unless it
    1168             is accompanied by a qvalue of 0. (As defined in <a href="p1-messaging.html#quality.values" title="Quality Values">Section 6.4</a> of <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, a qvalue of 0 means "not acceptable".)
    1169          </li>
    11701167         <li>The special "*" symbol in an Accept-Encoding field matches any available content-coding not explicitly listed in the header
    11711168            field.
    11721169         </li>
     1170         <li>If the representation has no content-coding, then it is acceptable by default unless specifically excluded by the Accept-Encoding
     1171            field stating either "identity;q=0" or "*;q=0" without a more specific entry for "identity".
     1172         </li>
     1173         <li>If the representation's content-coding is one of the content-codings listed in the Accept-Encoding field, then it is acceptable
     1174            unless it is accompanied by a qvalue of 0. (As defined in <a href="p1-messaging.html#quality.values" title="Quality Values">Section 6.4</a> of <a href="#Part1" id="rfc.xref.Part1.18"><cite title="HTTP/1.1, part 1: URIs, Connections, and Message Parsing">[Part1]</cite></a>, a qvalue of 0 means "not acceptable".)
     1175         </li>
    11731176         <li>If multiple content-codings are acceptable, then the acceptable content-coding with the highest non-zero qvalue is preferred.</li>
    1174          <li>The "identity" content-coding is always acceptable, unless specifically refused because the Accept-Encoding field includes
    1175             "identity;q=0", or because the field includes "*;q=0" and does not explicitly include the "identity" content-coding. If the
    1176             Accept-Encoding field-value is empty, then only the "identity" encoding is acceptable.
    1177          </li>
    11781177      </ol>
    1179       <p id="rfc.section.6.3.p.7">If an Accept-Encoding field is present in a request, but the server cannot send a response which is acceptable, then the server <em class="bcp14">SHOULD</em> send a response without any encoding (i.e., the "identity" encoding).
    1180       </p>
    1181       <p id="rfc.section.6.3.p.8">If no Accept-Encoding field is present in a request, the server <em class="bcp14">MAY</em> assume that the client will accept any content coding. In this case, if "identity" is one of the available content-codings,
    1182          then the server <em class="bcp14">SHOULD</em> use the "identity" content-coding, unless it has additional information that a different content-coding is meaningful to the
    1183          client.
     1178      <p id="rfc.section.6.3.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
     1179         in response. If an Accept-Encoding header field is present in a request and none of the available representations for the
     1180         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.
     1181      </p>
     1182      <p id="rfc.section.6.3.p.8">A request without an Accept-Encoding header field implies that the user agent will accept any content-coding in response,
     1183         but a representation without content-coding is preferred for compatibility with the widest variety of user agents.
    11841184      </p>
    11851185      <div class="note" id="rfc.section.6.3.p.9">
    1186          <p> <b>Note:</b> If the request does not include an Accept-Encoding field, and if the "identity" content-coding is unavailable, then content-codings
    1187             commonly understood by HTTP/1.0 clients (i.e., "gzip" and "compress") are preferred; some older clients improperly display
    1188             messages sent with other content-codings. The server might also make this decision based on information about the particular
    1189             user-agent or client.
    1190          </p>
    1191       </div>
    1192       <div class="note" id="rfc.section.6.3.p.10">
    11931186         <p> <b>Note:</b> Most HTTP/1.0 applications do not recognize or obey qvalues associated with content-codings. This means that qvalues will
    11941187            not work and are not permitted with x-gzip or x-compress.
    … …  
    12301223         </p>
    12311224      </div>
    1232       <div id="rfc.iref.c.7"></div>
     1225      <div id="rfc.iref.c.6"></div>
    12331226      <div id="rfc.iref.h.5"></div>
    12341227      <h2 id="rfc.section.6.5"><a href="#rfc.section.6.5">6.5</a>&nbsp;<a id="header.content-encoding" href="#header.content-encoding">Content-Encoding</a></h2>
    1235       <p id="rfc.section.6.5.p.1">The "Content-Encoding" header field indicates what content-codings have been applied to the representation, and thus what
    1236          decoding mechanisms must be applied in order to obtain the media-type referenced by the Content-Type header field. Content-Encoding
    1237          is primarily used to allow a representation to be compressed without losing the identity of its underlying media type.
     1228      <p id="rfc.section.6.5.p.1">The "Content-Encoding" header field indicates what content-codings have been applied to the representation beyond those inherent
     1229         in the media type, and thus what decoding mechanisms must be applied in order to obtain the media-type referenced by the Content-Type
     1230         header field. Content-Encoding is primarily used to allow a representation to be compressed without losing the identity of
     1231         its underlying media type.
    12381232      </p>
    12391233      <div id="rfc.figure.u.21"></div><pre class="inline"><span id="rfc.iref.g.20"></span>  <a href="#header.content-encoding" class="smpl">Content-Encoding</a> = 1#<a href="#content.codings" class="smpl">content-coding</a>
    … …  
    12451239         directive is present in the message.
    12461240      </p>
    1247       <p id="rfc.section.6.5.p.6">If the content-coding of a representation is not "identity", then the representation metadata <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;6.5</a>) that lists the non-identity content-coding(s) used.
    1248       </p>
    1249       <p id="rfc.section.6.5.p.7">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).
     1241      <p id="rfc.section.6.5.p.6">If the media type includes an inherent encoding, such as a data format that is always compressed, then that encoding would
     1242         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
     1243         would only be listed if, for some bizarre reason, it is applied a second time to form the representation. Likewise, an origin
     1244         server might choose to publish the same payload data as multiple representations that differ only in whether the coding is
     1245         defined as part of Content-Type or Content-Encoding, since some user agents will behave differently in their handling of each
     1246         response (e.g., open a "Save as ..." dialog instead of automatic decompression and rendering of content).
     1247      </p>
     1248      <p id="rfc.section.6.5.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;6.5</a>) that lists the content-coding(s) applied.
    12501249      </p>
    12511250      <p id="rfc.section.6.5.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.
    12521251      </p>
    1253       <div id="rfc.iref.c.8"></div>
     1252      <p id="rfc.section.6.5.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).
     1253      </p>
     1254      <div id="rfc.iref.c.7"></div>
    12541255      <div id="rfc.iref.h.6"></div>
    12551256      <h2 id="rfc.section.6.6"><a href="#rfc.section.6.6">6.6</a>&nbsp;<a id="header.content-language" href="#header.content-language">Content-Language</a></h2>
    … …  
    12771278      <p id="rfc.section.6.6.p.9">Content-Language <em class="bcp14">MAY</em> be applied to any media type — it is not limited to textual documents.
    12781279      </p>
    1279       <div id="rfc.iref.c.9"></div>
     1280      <div id="rfc.iref.c.8"></div>
    12801281      <div id="rfc.iref.h.7"></div>
    12811282      <h2 id="rfc.section.6.7"><a href="#rfc.section.6.7">6.7</a>&nbsp;<a id="header.content-location" href="#header.content-location">Content-Location</a></h2>
    … …  
    13191320      </p>
    13201321      <p id="rfc.section.6.7.p.9">If the Content-Location value is a partial URI, the partial URI is interpreted relative to the effective request URI.</p>
    1321       <div id="rfc.iref.c.10"></div>
     1322      <div id="rfc.iref.c.9"></div>
    13221323      <div id="rfc.iref.h.8"></div>
    13231324      <h2 id="rfc.section.6.8"><a href="#rfc.section.6.8">6.8</a>&nbsp;<a id="header.content-type" href="#header.content-type">Content-Type</a></h2>
    … …  
    20352036      <p id="rfc.section.E.18.p.1">None yet.</p>
    20362037      <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1>
    2037       <p class="noprint"><a href="#rfc.index.A">A</a> <a href="#rfc.index.B">B</a> <a href="#rfc.index.C">C</a> <a href="#rfc.index.D">D</a> <a href="#rfc.index.G">G</a> <a href="#rfc.index.H">H</a> <a href="#rfc.index.I">I</a> <a href="#rfc.index.M">M</a> <a href="#rfc.index.P">P</a> <a href="#rfc.index.R">R</a>
     2038      <p class="noprint"><a href="#rfc.index.A">A</a> <a href="#rfc.index.B">B</a> <a href="#rfc.index.C">C</a> <a href="#rfc.index.D">D</a> <a href="#rfc.index.G">G</a> <a href="#rfc.index.H">H</a> <a href="#rfc.index.M">M</a> <a href="#rfc.index.P">P</a> <a href="#rfc.index.R">R</a>
    20382039      </p>
    20392040      <div class="print2col">
    … …  
    20562057                        <li>deflate&nbsp;&nbsp;<a href="#rfc.iref.c.4">2.2</a></li>
    20572058                        <li>gzip&nbsp;&nbsp;<a href="#rfc.iref.c.5">2.2</a></li>
    2058                         <li>identity&nbsp;&nbsp;<a href="#rfc.iref.c.6">2.2</a></li>
    20592059                     </ul>
    20602060                  </li>
    20612061                  <li>compress (Coding Format)&nbsp;&nbsp;<a href="#rfc.iref.c.2">2.2</a></li>
    20622062                  <li>content negotiation&nbsp;&nbsp;<a href="#rfc.iref.c.1">1.1</a></li>
    2063                   <li>Content-Encoding header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-encoding.1">2.2</a>, <a href="#rfc.xref.header.content-encoding.2">4.1</a>, <a href="#rfc.iref.c.7"><b>6.5</b></a>, <a href="#rfc.xref.header.content-encoding.3">6.5</a>, <a href="#rfc.xref.header.content-encoding.4">7.1</a></li>
    2064                   <li>Content-Language header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-language.1">4.1</a>, <a href="#rfc.iref.c.8"><b>6.6</b></a>, <a href="#rfc.xref.header.content-language.2">7.1</a></li>
    2065                   <li>Content-Location header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-location.1">4.1</a>, <a href="#rfc.iref.c.9"><b>6.7</b></a>, <a href="#rfc.xref.header.content-location.2">7.1</a>, <a href="#rfc.xref.header.content-location.3">C</a></li>
    2066                   <li>Content-Type header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-type.1">2.3</a>, <a href="#rfc.xref.header.content-type.2">4.1</a>, <a href="#rfc.iref.c.10"><b>6.8</b></a>, <a href="#rfc.xref.header.content-type.3">7.1</a></li>
     2063                  <li>Content-Encoding header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-encoding.1">2.2</a>, <a href="#rfc.xref.header.content-encoding.2">4.1</a>, <a href="#rfc.iref.c.6"><b>6.5</b></a>, <a href="#rfc.xref.header.content-encoding.3">6.5</a>, <a href="#rfc.xref.header.content-encoding.4">7.1</a></li>
     2064                  <li>Content-Language header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-language.1">4.1</a>, <a href="#rfc.iref.c.7"><b>6.6</b></a>, <a href="#rfc.xref.header.content-language.2">7.1</a></li>
     2065                  <li>Content-Location header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-location.1">4.1</a>, <a href="#rfc.iref.c.8"><b>6.7</b></a>, <a href="#rfc.xref.header.content-location.2">7.1</a>, <a href="#rfc.xref.header.content-location.3">C</a></li>
     2066                  <li>Content-Type header field&nbsp;&nbsp;<a href="#rfc.xref.header.content-type.1">2.3</a>, <a href="#rfc.xref.header.content-type.2">4.1</a>, <a href="#rfc.iref.c.9"><b>6.8</b></a>, <a href="#rfc.xref.header.content-type.3">7.1</a></li>
    20672067               </ul>
    20682068            </li>
    … …  
    21162116                     </ul>
    21172117                  </li>
    2118                </ul>
    2119             </li>
    2120             <li><a id="rfc.index.I" href="#rfc.index.I"><b>I</b></a><ul>
    2121                   <li>identity (Coding Format)&nbsp;&nbsp;<a href="#rfc.iref.i.1">2.2</a></li>
    21222118               </ul>
    21232119            </li>
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