docs/manual/mod/mod_negotiation.html - httpd - Git at Google

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 <H1>Module mod_negotiation</h1>

 This module is contained in the <code>mod_negotiation.c</code> file, and
 is compiled in by default. It provides for
 <A HREF="content-negotiation.html">content negotiation</A>. Any document with
 mime type <code>application/x-type-map</code> will be processed by this module.
 <!--%plaintext &lt;?INDEX {\tt application/x-type-map} mime type&gt; -->

 <h2>Summary</h2>
 Content negotiation, or more accurately content selection, is the
 selection of the document that best matches the clients
 capabilities, from one of several available documents.
 There are two implementations of this.
 <ul>
 <li> A type map (a file with the mime type <code>application/x-type-map</code>)
 which explicitly lists the files containing the variants.
 <li> A MultiViews search (enabled by the MultiViews
 <A HREF="core.html#options">Option</A>, where the server does an implicit
 filename pattern match, and choose from amongst the results.
 </ul>

 <h3>Type maps</h3>
 A type map has the same format as RFC822 mail headers. It contains document
 descriptions separated by blank lines, with lines beginning with a hash
 character ('#') treated as comments. A document description consists of
 several header records; records may be continued on multiple lines if the
 continuation lines start with spaces. The leading space will be deleted
 and the lines concatenated. A header record consists of a keyword
 name, which always ends in a colon, followed by a value. Whitespace is allowed
 between the header name and value, and between the tokens of value.

 The headers
 allowed are:

 <dl>
 <dt>Content-Encoding:
 <dd>The encoding of the file. Currently only two encodings are recognised
 by http; <code>x-compress</code> for compressed files, and <code>x-gzip</code>
 for gzipped files.
 <dt>Content-Language:
 <dd>The language of the variant, as an Internet standard language code, such
 as <code>en</code>.
 <dt>Content-Length:
 <dd>The length of the file, in bytes. If this header is not present, then
 the actual length of the file is used.
 <dt>Content-Type:
 <dd>The MIME media type of the document, with optional parameters.
 parameters are separated from the media type and from one another by
 semi-colons. Parameter syntax is name=value; allowed parameters are:
 <dl>
 <dt>level
 <dd>the value is an integer, which specifies the version of the media type.
 For <code>text/html</code> this defaults to 2, otherwise 0.
 <dt>qs
 <dd>the value is a floating-point number with value between 0. and 1.
 It indications the 'quality' of this variant.
 </dl>
 Example:
 <blockquote><code>Content-Type: image/jpeg; qs=0.8</code></blockquote>
 <dt>URI:
 <dd>The path to the file containing this variant, relative to the map file.
 </dl>

 <h3>MultiViews</h3>
 A MultiViews search is enabled by the MultiViews
 <A HREF="core.html#options">Option</A>.
 If the server receives a request for <code>/some/dir/foo</code> and
 <code>/some/dir/foo</code> does <em>not</em> exist, then the server reads the
 directory looking for all files named <code>foo.*</code>, and effectively
 fakes up a type map which names all those files, assigning them the same media
 types and content-encodings it would have if the client had asked for
 one of them by name.  It then chooses the best match to the client's
 requirements, and returns that document.<p>


 <!--%hypertext -->
 <h2>Directives</h2>
 <ul>
 <li><A href="#cachenegotiateddocs">CacheNegotiatedDocs</a>
 <li><A HREF="#languagepriority">LanguagePriority</A>
 </ul>
 <hr>
 <!--/%hypertext -->

 <A name="cachenegotiateddocs"><h2>CacheNegotiatedDocs</h2></A>
 <strong>Syntax:</strong> CacheNegotiatedDocs<br>
 <Strong>Context:</strong> server config<br>
 <strong>Status:</strong> Base<br>
 <strong>Module:</strong> mod_negotiation<br>
 <strong>Compatibility:</strong> CacheNegotiatedDocs is only available
 in Apache 1.1 and later.<p>

 <p>If set, this directive allows content-negotiated documents to be cached
 by
 proxy servers. This could mean that clients behind those proxys could
 retrieve versions of the documents that are not the best match for
 their abilities, but it will make caching more efficient.</p>

 <!--%hypertext -->
 <A name="languagepriority"><h2>LanguagePriority</h2></A>
 <!--%plaintext &lt;?INDEX {\tt LanguagePriority} directive&gt; -->
 <strong>Syntax:</strong> LanguagePriority <em>mime-lang mime-lang...</em><br>
 <Strong>Context:</strong> server config, virtual host, directory, .htaccess<br>
 <Strong>Override:</strong> FileInfo<br>
 <strong>Status:</strong> Base<br>
 <strong>Module:</strong> mod_negotiation<p>

 The LanguagePriority sets the precedence of language variants for the case
 where the client does not express a preference, when handling a
 MultiViews request. The list of <em>mime-lang</em> are in order of decreasing
 preference. Example:
 <blockquote><code>LanguagePriority en fr de</code></blockquote>
 For a request for <code>foo.html</code>, where <code>foo.html.fr</code>
 and <code>foo.html.de</code> both existed, but the browser did not express
 a language preference, then <code>foo.html.fr</code> would be returned.<p>
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	<H1>Module mod_negotiation</h1>

	This module is contained in the <code>mod_negotiation.c</code> file, and
	is compiled in by default. It provides for
	<A HREF="content-negotiation.html">content negotiation</A>. Any document with
	mime type <code>application/x-type-map</code> will be processed by this module.
	<!--%plaintext <?INDEX {\tt application/x-type-map} mime type> -->

	<h2>Summary</h2>
	Content negotiation, or more accurately content selection, is the
	selection of the document that best matches the clients
	capabilities, from one of several available documents.
	There are two implementations of this.
	<ul>
	<li> A type map (a file with the mime type <code>application/x-type-map</code>)
	which explicitly lists the files containing the variants.
	<li> A MultiViews search (enabled by the MultiViews
	<A HREF="core.html#options">Option</A>, where the server does an implicit
	filename pattern match, and choose from amongst the results.
	</ul>

	<h3>Type maps</h3>
	A type map has the same format as RFC822 mail headers. It contains document
	descriptions separated by blank lines, with lines beginning with a hash
	character ('#') treated as comments. A document description consists of
	several header records; records may be continued on multiple lines if the
	continuation lines start with spaces. The leading space will be deleted
	and the lines concatenated. A header record consists of a keyword
	name, which always ends in a colon, followed by a value. Whitespace is allowed
	between the header name and value, and between the tokens of value.

	The headers
	allowed are:

	<dl>
	<dt>Content-Encoding:
	<dd>The encoding of the file. Currently only two encodings are recognised
	by http; <code>x-compress</code> for compressed files, and <code>x-gzip</code>
	for gzipped files.
	<dt>Content-Language:
	<dd>The language of the variant, as an Internet standard language code, such
	as <code>en</code>.
	<dt>Content-Length:
	<dd>The length of the file, in bytes. If this header is not present, then
	the actual length of the file is used.
	<dt>Content-Type:
	<dd>The MIME media type of the document, with optional parameters.
	parameters are separated from the media type and from one another by
	semi-colons. Parameter syntax is name=value; allowed parameters are:
	<dl>
	<dt>level
	<dd>the value is an integer, which specifies the version of the media type.
	For <code>text/html</code> this defaults to 2, otherwise 0.
	<dt>qs
	<dd>the value is a floating-point number with value between 0. and 1.
	It indications the 'quality' of this variant.
	</dl>
	Example:
	<blockquote><code>Content-Type: image/jpeg; qs=0.8</code></blockquote>
	<dt>URI:
	<dd>The path to the file containing this variant, relative to the map file.
	</dl>

	<h3>MultiViews</h3>
	A MultiViews search is enabled by the MultiViews
	<A HREF="core.html#options">Option</A>.
	If the server receives a request for <code>/some/dir/foo</code> and
	<code>/some/dir/foo</code> does <em>not</em> exist, then the server reads the
	directory looking for all files named <code>foo.*</code>, and effectively
	fakes up a type map which names all those files, assigning them the same media
	types and content-encodings it would have if the client had asked for
	one of them by name. It then chooses the best match to the client's
	requirements, and returns that document.<p>


	<!--%hypertext -->
	<h2>Directives</h2>
	<ul>
	<li><A href="#cachenegotiateddocs">CacheNegotiatedDocs</a>
	<li><A HREF="#languagepriority">LanguagePriority</A>
	</ul>
	<hr>
	<!--/%hypertext -->

	<A name="cachenegotiateddocs"><h2>CacheNegotiatedDocs</h2></A>
	<strong>Syntax:</strong> CacheNegotiatedDocs<br>
	<Strong>Context:</strong> server config<br>
	<strong>Status:</strong> Base<br>
	<strong>Module:</strong> mod_negotiation<br>
	<strong>Compatibility:</strong> CacheNegotiatedDocs is only available
	in Apache 1.1 and later.<p>

	<p>If set, this directive allows content-negotiated documents to be cached
	by
	proxy servers. This could mean that clients behind those proxys could
	retrieve versions of the documents that are not the best match for
	their abilities, but it will make caching more efficient.</p>

	<!--%hypertext -->
	<A name="languagepriority"><h2>LanguagePriority</h2></A>
	<!--%plaintext <?INDEX {\tt LanguagePriority} directive> -->
	<strong>Syntax:</strong> LanguagePriority <em>mime-lang mime-lang...</em><br>
	<Strong>Context:</strong> server config, virtual host, directory, .htaccess<br>
	<Strong>Override:</strong> FileInfo<br>
	<strong>Status:</strong> Base<br>
	<strong>Module:</strong> mod_negotiation<p>

	The LanguagePriority sets the precedence of language variants for the case
	where the client does not express a preference, when handling a
	MultiViews request. The list of <em>mime-lang</em> are in order of decreasing
	preference. Example:
	<blockquote><code>LanguagePriority en fr de</code></blockquote>
	For a request for <code>foo.html</code>, where <code>foo.html.fr</code>
	and <code>foo.html.de</code> both existed, but the browser did not express
	a language preference, then <code>foo.html.fr</code> would be returned.<p>
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