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24 <div id="page-content">
25 <div id="preamble"><h1>Apache Module mod_negotiation</h1>
27 <p><span>Available Languages: </span><a href="../en/mod/mod_negotiation.html" title="English"> en </a> |
28 <a href="../fr/mod/mod_negotiation.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
29 <a href="../ja/mod/mod_negotiation.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
31 <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>
32 <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Base</td></tr>
33 <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>negotiation_module</td></tr>
34 <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_negotiation.c</td></tr></table>
37 <p>Content negotiation, or more accurately content selection, is
38 the selection of the document that best matches the clients
39 capabilities, from one of several available documents. There
40 are two implementations of this.</p>
43 <li>A type map (a file with the handler
44 <code>type-map</code>) which explicitly lists the files
45 containing the variants.</li>
47 <li>A Multiviews search (enabled by the <code>Multiviews</code>
48 <code class="directive"><a href="../mod/core.html#options">Options</a></code>), where the server does
49 an implicit filename pattern match, and choose from amongst the
53 <div id="quickview"><h3 class="directives">Directives</h3>
55 <li><img alt="" src="../images/down.gif" /> <a href="#cachenegotiateddocs">CacheNegotiatedDocs</a></li>
56 <li><img alt="" src="../images/down.gif" /> <a href="#forcelanguagepriority">ForceLanguagePriority</a></li>
57 <li><img alt="" src="../images/down.gif" /> <a href="#languagepriority">LanguagePriority</a></li>
61 <li><img alt="" src="../images/down.gif" /> <a href="#typemaps">Type maps</a></li>
62 <li><img alt="" src="../images/down.gif" /> <a href="#multiviews">Multiviews</a></li>
63 </ul><h3>See also</h3>
65 <li><code class="directive"><a href="../mod/core.html#options">Options</a></code></li>
66 <li><code class="module"><a href="../mod/mod_mime.html">mod_mime</a></code></li>
67 <li><a href="../content-negotiation.html">Content
69 <li><a href="../env.html">Environment Variables</a></li>
70 </ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
71 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
73 <h2><a name="typemaps" id="typemaps">Type maps</a></h2>
74 <p>A type map has a format similar to RFC822 mail headers. It
75 contains document descriptions separated by blank lines, with
76 lines beginning with a hash character ('#') treated as
77 comments. A document description consists of several header
78 records; records may be continued on multiple lines if the
79 continuation lines start with spaces. The leading space will be
80 deleted and the lines concatenated. A header record consists of
81 a keyword name, which always ends in a colon, followed by a
82 value. Whitespace is allowed between the header name and value,
83 and between the tokens of value. The headers allowed are: </p>
86 <dt><code>Content-Encoding:</code></dt>
87 <dd>The encoding of the file. Apache only recognizes
88 encodings that are defined by an <code class="directive"><a href="../mod/mod_mime.html#addencoding">AddEncoding</a></code> directive.
89 This normally includes the encodings <code>x-compress</code>
90 for compress'd files, and <code>x-gzip</code> for gzip'd
91 files. The <code>x-</code> prefix is ignored for encoding
94 <dt><code>Content-Language:</code></dt>
95 <dd>The language(s) of the variant, as an Internet standard
96 language tag (<a href="http://www.ietf.org/rfc/rfc1766.txt">RFC 1766</a>). An example is <code>en</code>,
97 meaning English. If the variant contains more than one
98 language, they are separated by a comma.</dd>
100 <dt><code>Content-Length:</code></dt>
101 <dd>The length of the file, in bytes. If this header is not
102 present, then the actual length of the file is used.</dd>
104 <dt><code>Content-Type:</code></dt>
107 The <a class="glossarylink" href="../glossary.html#mime-type" title="see glossary">MIME media type</a> of
108 the document, with optional parameters. Parameters are
109 separated from the media type and from one another by a
110 semi-colon, with a syntax of <code>name=value</code>. Common
114 <dt><code>level</code></dt>
115 <dd>an integer specifying the version of the media type.
116 For <code>text/html</code> this defaults to 2, otherwise
119 <dt><code>qs</code></dt>
120 <dd>a floating-point number with a value in the range 0[.000]
121 to 1[.000], indicating the relative 'quality' of this variant
122 compared to the other available variants, independent of
123 the client's capabilities. For example, a jpeg file is
124 usually of higher source quality than an ascii file if it
125 is attempting to represent a photograph. However, if the
126 resource being represented is ascii art, then an ascii
127 file would have a higher source quality than a jpeg file.
128 All <code>qs</code> values are therefore specific to a given
132 <div class="example"><h3>Example</h3><p><code>
133 Content-Type: image/jpeg; qs=0.8
137 <dt><code>URI:</code></dt>
138 <dd>uri of the file containing the variant (of the given
139 media type, encoded with the given content encoding). These
140 are interpreted as URLs relative to the map file; they must
141 be on the same server, and they must refer to files to
142 which the client would be granted access if they were to be
143 requested directly.</dd>
145 <dt><code>Body:</code></dt>
146 <dd>The actual content of the resource may
147 be included in the type-map file using the Body header. This
148 header must contain a string that designates a delimiter for
149 the body content. Then all following lines in the type map
150 file will be considered part of the resource body until the
151 delimiter string is found.
153 <div class="example"><h3>Example:</h3><p><code>
154 Body:----xyz----<br />
157 <p>Content of the page.</p><br />
165 <p>Consider, for example, a resource called
166 <code>document.html</code> which is available in English, French,
167 and German. The files for each of these are called
168 <code>document.html.en</code>, <code>document.html.fr</code>, and
169 <code>document.html.de</code>, respectively. The type map file will
170 be called <code>document.html.var</code>, and will contain the
173 <div class="example"><p><code>
174 URI: document.html<br />
176 Content-language: en<br />
177 Content-type: text/html<br />
178 URI: document.html.en<br />
180 Content-language: fr<br />
181 Content-type: text/html<br />
182 URI: document.html.fr<br />
184 Content-language: de<br />
185 Content-type: text/html<br />
186 URI: document.html.de<br />
191 <p>All four of these files should be placed in the same directory,
192 and the <code>.var</code> file should be associated with the
193 <code>type-map</code> handler with an <code class="directive"><a href="../mod/mod_mime.html#addhandler">AddHandler</a></code> directive:</p>
195 <pre class="prettyprint lang-config">
196 AddHandler type-map .var
200 <p>A request for <code>document.html</code> in this directory will
201 result in <code>document.html.var</code> being consulted, and the
202 variant chosen which most closely matches the language preference
203 specified in the user's <code>Accept-Language</code> request
205 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
206 <div class="section">
207 <h2><a name="multiviews" id="multiviews">Multiviews</a></h2>
208 <p>A Multiviews search is enabled by the <code>Multiviews</code>
209 <code class="directive"><a href="../mod/core.html#options">Options</a></code>. If the server receives a
210 request for <code>/some/dir/foo</code> and
211 <code>/some/dir/foo</code> does <em>not</em> exist, then the
212 server reads the directory looking for all files named
213 <code>foo.*</code>, and effectively fakes up a type map which
214 names all those files, assigning them the same media types and
215 content-encodings it would have if the client had asked for one
216 of them by name. It then chooses the best match to the client's
217 requirements, and returns that document.</p>
219 <p>The <code class="directive"><a href="../mod/mod_mime.html#multiviewsmatch">MultiviewsMatch</a></code>
220 directive configures whether Apache will consider files
221 that do not have content negotiation meta-information assigned
222 to them when choosing files.</p>
224 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
225 <div class="directive-section"><h2><a name="CacheNegotiatedDocs" id="CacheNegotiatedDocs">CacheNegotiatedDocs</a> <a name="cachenegotiateddocs" id="cachenegotiateddocs">Directive</a></h2>
226 <table class="directive">
227 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Allows content-negotiated documents to be
228 cached by proxy servers</td></tr>
229 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>CacheNegotiatedDocs On|Off</code></td></tr>
230 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>CacheNegotiatedDocs Off</code></td></tr>
231 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr>
232 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
233 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_negotiation</td></tr>
235 <p>If set, this directive allows content-negotiated documents
236 to be cached by proxy servers. This could mean that clients
237 behind those proxys could retrieve versions of the documents
238 that are not the best match for their abilities, but it will
239 make caching more efficient.</p>
241 <p>This directive only applies to requests which come from
242 HTTP/1.0 browsers. HTTP/1.1 provides much better control over
243 the caching of negotiated documents, and this directive has no
244 effect in responses to HTTP/1.1 requests.</p>
248 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
249 <div class="directive-section"><h2><a name="ForceLanguagePriority" id="ForceLanguagePriority">ForceLanguagePriority</a> <a name="forcelanguagepriority" id="forcelanguagepriority">Directive</a></h2>
250 <table class="directive">
251 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Action to take if a single acceptable document is not
253 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ForceLanguagePriority None|Prefer|Fallback [Prefer|Fallback]</code></td></tr>
254 <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ForceLanguagePriority Prefer</code></td></tr>
255 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
256 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
257 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
258 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_negotiation</td></tr>
260 <p>The <code class="directive">ForceLanguagePriority</code> directive uses
261 the given <code class="directive"><a href="#languagepriority">LanguagePriority</a></code> to satisfy
262 negotiation where the server could otherwise not return a single
263 matching document.</p>
265 <p><code>ForceLanguagePriority Prefer</code> uses
266 <code>LanguagePriority</code> to serve a one valid result, rather
267 than returning an HTTP result 300 (MULTIPLE CHOICES) when there
268 are several equally valid choices. If the directives below were
269 given, and the user's <code>Accept-Language</code> header assigned
270 <code>en</code> and <code>de</code> each as quality <code>.500</code>
271 (equally acceptable) then the first matching variant, <code>en</code>,
274 <pre class="prettyprint lang-config">
275 LanguagePriority en fr de
276 ForceLanguagePriority Prefer
280 <p><code>ForceLanguagePriority Fallback</code> uses
281 <code class="directive"><a href="#languagepriority">LanguagePriority</a></code> to
282 serve a valid result, rather than returning an HTTP result 406
283 (NOT ACCEPTABLE). If the directives below were given, and the user's
284 <code>Accept-Language</code> only permitted an <code>es</code>
285 language response, but such a variant isn't found, then the first
286 variant from the <code class="directive"><a href="#languagepriority">LanguagePriority</a></code> list below will be served.</p>
288 <pre class="prettyprint lang-config">
289 LanguagePriority en fr de
290 ForceLanguagePriority Fallback
294 <p>Both options, <code>Prefer</code> and <code>Fallback</code>, may be
295 specified, so either the first matching variant from <code class="directive"><a href="#languagepriority">LanguagePriority</a></code> will be served if
296 more than one variant is acceptable, or first available document will
297 be served if none of the variants matched the client's acceptable list
302 <li><code class="directive"><a href="../mod/mod_mime.html#addlanguage">AddLanguage</a></code></li>
305 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
306 <div class="directive-section"><h2><a name="LanguagePriority" id="LanguagePriority">LanguagePriority</a> <a name="languagepriority" id="languagepriority">Directive</a></h2>
307 <table class="directive">
308 <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>The precendence of language variants for cases where
309 the client does not express a preference</td></tr>
310 <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>LanguagePriority <var>MIME-lang</var> [<var>MIME-lang</var>]
312 <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
313 <tr><th><a href="directive-dict.html#Override">Override:</a></th><td>FileInfo</td></tr>
314 <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Base</td></tr>
315 <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_negotiation</td></tr>
317 <p>The <code class="directive">LanguagePriority</code> sets the precedence
318 of language variants for the case where the client does not
319 express a preference, when handling a Multiviews request. The list
320 of <var>MIME-lang</var> are in order of decreasing preference.</p>
322 <pre class="prettyprint lang-config">
323 LanguagePriority en fr de
327 <p>For a request for <code>foo.html</code>, where
328 <code>foo.html.fr</code> and <code>foo.html.de</code> both
329 existed, but the browser did not express a language preference,
330 then <code>foo.html.fr</code> would be returned.</p>
332 <p>Note that this directive only has an effect if a 'best'
333 language cannot be determined by any other means or the <code class="directive"><a href="#forcelanguagepriority">ForceLanguagePriority</a></code> directive
334 is not <code>None</code>. In general, the client determines the
335 language preference, not the server.</p>
339 <li><code class="directive"><a href="../mod/mod_mime.html#addlanguage">AddLanguage</a></code></li>
343 <div class="bottomlang">
344 <p><span>Available Languages: </span><a href="../en/mod/mod_negotiation.html" title="English"> en </a> |
345 <a href="../fr/mod/mod_negotiation.html" hreflang="fr" rel="alternate" title="Français"> fr </a> |
346 <a href="../ja/mod/mod_negotiation.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a></p>
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