apache/docs/manual/mod/mod_negotiation.html.en

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   8 <title>mod_negotiation - Apache HTTP Server</title>
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  21 <div id="page-content">
  22 <div id="preamble"><h1>Apache Module mod_negotiation</h1>
  23 <div class="toplang">
  24 <p><span>Available Languages: </span><a href="../en/mod/mod_negotiation.html" title="English">&nbsp;en&nbsp;</a> |
  25 <a href="../ja/mod/mod_negotiation.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a></p>
  26 </div>
  27 <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Provides for <a href="../content-negotiation.html">content negotiation</a></td></tr>
  28 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr>
  29 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>negotiation_module</td></tr>
  30 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_negotiation.c</td></tr></table>
  31 <h3>Summary</h3>
  32
  33     <p>Content negotiation, or more accurately content selection, is
  34     the selection of the document that best matches the clients
  35     capabilities, from one of several available documents. There
  36     are two implementations of this.</p>
  37
  38     <ul>
  39       <li>A type map (a file with the handler
  40       <code>type-map</code>) which explicitly lists the files
  41       containing the variants.</li>
  42
  43       <li>A MultiViews search (enabled by the <code>MultiViews</code>
  44       <code class="directive"><a href="../mod/core.html#options">Options</a></code>), where the server does
  45       an implicit filename pattern match, and choose from amongst the
  46       results.</li>
  47     </ul>
  48 </div>
  49 <div id="quickview"><h3 class="directives">Directives</h3>
  50 <ul id="toc">
  51 <li><img alt="" src="../images/down.gif" /> <a href="#cachenegotiateddocs">CacheNegotiatedDocs</a></li>
  52 <li><img alt="" src="../images/down.gif" /> <a href="#forcelanguagepriority">ForceLanguagePriority</a></li>
  53 <li><img alt="" src="../images/down.gif" /> <a href="#languagepriority">LanguagePriority</a></li>
  54 </ul>
  55 <h3>Topics</h3>
  56 <ul id="topics">
  57 <li><img alt="" src="../images/down.gif" /> <a href="#typemaps">Type maps</a></li>
  58 <li><img alt="" src="../images/down.gif" /> <a href="#multiviews">MultiViews</a></li>
  59 </ul><h3>See also</h3>
  60 <ul class="seealso">
  61 <li><code class="directive"><a href="../mod/core.html#options">Options</a></code></li>
  62 <li><code class="module"><a href="../mod/mod_mime.html">mod_mime</a></code></li>
  63 <li><a href="../content-negotiation.html">Content
  64 Negotiation</a></li>
  65 <li><a href="../env.html">Environment Variables</a></li>
  66 </ul></div>
  67 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
  68 <div class="section">
  69 <h2><a name="typemaps" id="typemaps">Type maps</a></h2>
  70     <p>A type map has a format similar to RFC822 mail headers. It
  71     contains document descriptions separated by blank lines, with
  72     lines beginning with a hash character ('#') treated as
  73     comments. A document description consists of several header
  74     records; records may be continued on multiple lines if the
  75     continuation lines start with spaces. The leading space will be
  76     deleted and the lines concatenated. A header record consists of
  77     a keyword name, which always ends in a colon, followed by a
  78     value. Whitespace is allowed between the header name and value,
  79     and between the tokens of value. The headers allowed are: </p>
  80
  81     <dl>
  82       <dt><code>Content-Encoding:</code></dt>
  83       <dd>The encoding of the file. Apache only recognizes
  84       encodings that are defined by an <code class="directive"><a href="../mod/mod_mime.html#addencoding">AddEncoding</a></code> directive.
  85       This normally includes the encodings <code>x-compress</code>
  86       for compress'd files, and <code>x-gzip</code> for gzip'd
  87       files. The <code>x-</code> prefix is ignored for encoding
  88       comparisons.</dd>
  89
  90       <dt><code>Content-Language:</code></dt>
  91       <dd>The language(s) of the variant, as an Internet standard
  92       language tag (<a href="http://www.ietf.org/rfc/rfc1766.txt">RFC 1766</a>). An example is <code>en</code>,
  93       meaning English. If the variant contains more than one
  94       language, they are separated by a comma.</dd>
  95
  96       <dt><code>Content-Length:</code></dt>
  97       <dd>The length of the file, in bytes. If this header is not
  98       present, then the actual length of the file is used.</dd>
  99
 100       <dt><code>Content-Type:</code></dt>
 101
 102       <dd>
 103         The <a class="glossarylink" href="../glossary.html#mime-type" title="see glossary">MIME media type</a> of
 104         the document, with optional parameters. Parameters are
 105         separated from the media type and from one another by a
 106         semi-colon, with a syntax of <code>name=value</code>. Common
 107         parameters include:
 108
 109         <dl>
 110           <dt><code>level</code></dt>
 111           <dd>an integer specifying the version of the media type.
 112           For <code>text/html</code> this defaults to 2, otherwise
 113           0.</dd>
 114
 115           <dt><code>qs</code></dt>
 116           <dd>a floating-point number with a value in the range 0.0
 117           to 1.0, indicating the relative 'quality' of this variant
 118           compared to the other available variants, independent of
 119           the client's capabilities. For example, a jpeg file is
 120           usually of higher source quality than an ascii file if it
 121           is attempting to represent a photograph. However, if the
 122           resource being represented is ascii art, then an ascii
 123           file would have a higher source quality than a jpeg file.
 124           All <code>qs</code> values are therefore specific to a given
 125           resource.</dd>
 126         </dl>
 127
 128         <div class="example"><h3>Example</h3><p><code>
 129           Content-Type: image/jpeg; qs=0.8
 130         </code></p></div>
 131       </dd>
 132
 133       <dt><code>URI:</code></dt>
 134       <dd>uri of the file containing the variant (of the given
 135       media type, encoded with the given content encoding). These
 136       are interpreted as URLs relative to the map file; they must
 137       be on the same server (!), and they must refer to files to
 138       which the client would be granted access if they were to be
 139       requested directly.</dd>
 140
 141       <dt><code>Body:</code></dt>
 142       <dd>New in Apache 2.0, the actual content of the resource may
 143       be included in the type-map file using the Body header.  This
 144       header must contain a string that designates a delimiter for
 145       the body content. Then all following lines in the type map
 146       file will be considered part of the resource body until the
 147       delimiter string is found.
 148
 149       <div class="example"><h3>Example:</h3><p><code>
 150         Body:----xyz----<br />
 151         &lt;html&gt;<br />
 152         &lt;body&gt;<br />
 153         &lt;p&gt;Content of the page.&lt;/p&gt;<br />
 154         &lt;/body&gt;<br />
 155         &lt;/html&gt;<br />
 156         ----xyz----
 157       </code></p></div>
 158       </dd>
 159     </dl>
 160 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 161 <div class="section">
 162 <h2><a name="multiviews" id="multiviews">MultiViews</a></h2>
 163     <p>A MultiViews search is enabled by the <code>MultiViews</code>
 164     <code class="directive"><a href="../mod/core.html#options">Options</a></code>. If the server receives a
 165     request for <code>/some/dir/foo</code> and
 166     <code>/some/dir/foo</code> does <em>not</em> exist, then the
 167     server reads the directory looking for all files named
 168     <code>foo.*</code>, and effectively fakes up a type map which
 169     names all those files, assigning them the same media types and
 170     content-encodings it would have if the client had asked for one
 171     of them by name. It then chooses the best match to the client's
 172     requirements, and returns that document.</p>
 173
 174     <p>The <code class="directive"><a href="../mod/mod_mime.html#multiviewsmatch">MultiViewsMatch</a></code>
 175     directive configures whether Apache will consider files
 176     that do not have content negotiation meta-information assigned
 177     to them when choosing files.</p>
 178 </div>
 179 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 180 <div class="directive-section"><h2><a name="CacheNegotiatedDocs" id="CacheNegotiatedDocs">CacheNegotiatedDocs</a> <a name="cachenegotiateddocs" id="cachenegotiateddocs">Directive</a></h2>
 181 <table class="directive">
 182 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Allows content-negotiated documents to be
 183 cached by proxy servers</td></tr>
 184 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheNegotiatedDocs On|Off</code></td></tr>
 185 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheNegotiatedDocs Off</code></td></tr>
 186 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
 187 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
 188 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_negotiation</td></tr>
 189 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>The syntax changed in version 2.0.</td></tr>
 190 </table>
 191     <p>If set, this directive allows content-negotiated documents
 192     to be cached by proxy servers. This could mean that clients
 193     behind those proxys could retrieve versions of the documents
 194     that are not the best match for their abilities, but it will
 195     make caching more efficient.</p>
 196
 197     <p>This directive only applies to requests which come from
 198     HTTP/1.0 browsers. HTTP/1.1 provides much better control over
 199     the caching of negotiated documents, and this directive has no
 200     effect in responses to HTTP/1.1 requests.</p>
 201
 202     <p>Prior to version 2.0,
 203     <code class="directive">CacheNegotiatedDocs</code> did not take an
 204     argument; it was turned on by the presence of the directive by
 205     itself.</p>
 206
 207 </div>
 208 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 209 <div class="directive-section"><h2><a name="ForceLanguagePriority" id="ForceLanguagePriority">ForceLanguagePriority</a> <a name="forcelanguagepriority" id="forcelanguagepriority">Directive</a></h2>
 210 <table class="directive">
 211 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Action to take if a single acceptable document is not
 212 found</td></tr>
 213 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ForceLanguagePriority None|Prefer|Fallback [Prefer|Fallback]</code></td></tr>
 214 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ForceLanguagePriority Prefer</code></td></tr>
 215 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 216 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
 217 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
 218 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_negotiation</td></tr>
 219 <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.0.30 and later</td></tr>
 220 </table>
 221     <p>The <code class="directive">ForceLanguagePriority</code> directive uses
 222     the given <code class="directive"><a href="#languagepriority">LanguagePriority</a></code> to satisfy
 223     negotation where the server could otherwise not return a single
 224     matching document.</p>
 225
 226     <p><code>ForceLanguagePriority Prefer</code> uses
 227     <code>LanguagePriority</code> to serve a one valid result, rather
 228     than returning an HTTP result 300 (MULTIPLE CHOICES) when there
 229     are several equally valid choices.  If the directives below were
 230     given, and the user's <code>Accept-Language</code> header assigned
 231     <code>en</code> and <code>de</code> each as quality <code>.500</code>
 232     (equally acceptable) then the first matching variant, <code>en</code>,
 233     will be served.</p>
 234
 235     <div class="example"><p><code>
 236       LanguagePriority en fr de<br />
 237       ForceLanguagePriority Prefer
 238     </code></p></div>
 239
 240     <p><code>ForceLanguagePriority Fallback</code> uses
 241     <code class="directive"><a href="#languagepriority">LanguagePriority</a></code> to
 242     serve a valid result, rather than returning an HTTP result 406
 243     (NOT ACCEPTABLE). If the directives below were given, and the user's
 244     <code>Accept-Language</code> only permitted an <code>es</code>
 245     language response, but such a variant isn't found, then the first
 246     variant from the <code class="directive"><a href="#languagepriority">LanguagePriority</a></code> list below will be served.</p>
 247
 248     <div class="example"><p><code>
 249       LanguagePriority en fr de<br />
 250       ForceLanguagePriority Fallback
 251     </code></p></div>
 252
 253     <p>Both options, <code>Prefer</code> and <code>Fallback</code>, may be
 254     specified, so either the first matching variant from <code class="directive"><a href="#languagepriority">LanguagePriority</a></code> will be served if
 255     more than one variant is acceptable, or first available document will
 256     be served if none of the variants matched the client's acceptable list
 257     of languages.</p>
 258
 259 <h3>See also</h3>
 260 <ul>
 261 <li><code class="directive"><a href="../mod/mod_mime.html#addlanguage">AddLanguage</a></code></li>
 262 </ul>
 263 </div>
 264 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
 265 <div class="directive-section"><h2><a name="LanguagePriority" id="LanguagePriority">LanguagePriority</a> <a name="languagepriority" id="languagepriority">Directive</a></h2>
 266 <table class="directive">
 267 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The precendence of language variants for cases where
 268 the client does not express a preference</td></tr>
 269 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LanguagePriority <var>MIME-lang</var> [<var>MIME-lang</var>]
 270 ...</code></td></tr>
 271 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
 272 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
 273 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
 274 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_negotiation</td></tr>
 275 </table>
 276     <p>The <code class="directive">LanguagePriority</code> sets the precedence
 277     of language variants for the case where the client does not
 278     express a preference, when handling a MultiViews request. The list
 279     of <var>MIME-lang</var> are in order of decreasing preference.</p>
 280
 281     <div class="example"><h3>Example:</h3><p><code>
 282       LanguagePriority en fr de
 283     </code></p></div>
 284
 285     <p>For a request for <code>foo.html</code>, where
 286     <code>foo.html.fr</code> and <code>foo.html.de</code> both
 287     existed, but the browser did not express a language preference,
 288     then <code>foo.html.fr</code> would be returned.</p>
 289
 290     <p>Note that this directive only has an effect if a 'best'
 291     language cannot be determined by any other means or the <code class="directive"><a href="#forcelanguagepriority">ForceLanguagePriority</a></code> directive
 292     is not <code>None</code>. In general, the client determines the
 293     language preference, not the server.</p>
 294
 295 <h3>See also</h3>
 296 <ul>
 297 <li><code class="directive"><a href="../mod/mod_mime.html#addlanguage">AddLanguage</a></code></li>
 298 </ul>
 299 </div>
 300 </div>
 301 <div class="bottomlang">
 302 <p><span>Available Languages: </span><a href="../en/mod/mod_negotiation.html" title="English">&nbsp;en&nbsp;</a> |
 303 <a href="../ja/mod/mod_negotiation.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a></p>
 304 </div><div id="footer">
 305 <p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
 306 <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div>
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