APACHE_1_3_42/htdocs/manual/mod/mod_negotiation.html.en - httpd - Git at Google

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     <title>Apache module mod_negotiation</title>
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     <h1 align="CENTER">Module mod_negotiation</h1>

     <p>This module provides for <a
     href="../content-negotiation.html">content negotiation</a>.</p>

     <p><a href="module-dict.html#Status"
     rel="Help"><strong>Status:</strong></a> Base<br />
      <a href="module-dict.html#SourceFile"
     rel="Help"><strong>Source File:</strong></a>
     mod_negotiation.c<br />
      <a href="module-dict.html#ModuleIdentifier"
     rel="Help"><strong>Module Identifier:</strong></a>
     negotiation_module</p>

     <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 handler
       <code>type-map</code>) which explicitly lists the files
       containing the variants.</li>

       <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.</li>
     </ul>

     <h2>Directives</h2>

     <ul>
       <li><a
       href="#cachenegotiateddocs">CacheNegotiatedDocs</a></li>

       <li><a href="#languagepriority">LanguagePriority</a></li>
     </ul>
     <strong>See also</strong>: <a
     href="./mod_mime.html#defaultlanguage">DefaultLanguage</a>, <a
     href="./mod_mime.html#addencoding">AddEncoding</a>, <a
     href="./mod_mime.html#addlanguage">AddLanguage</a>, <a
     href="./mod_mime.html#addtype">AddType</a>, and <a
     href="core.html#options">Options</a>.

     <h2>Type maps</h2>
     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:</dt>

       <dd>The encoding of the file. Apache only recognizes
       encodings that are defined by an <a
       href="mod_mime.html#addencoding">AddEncoding</a> directive.
       This normally includes the encodings <code>x-compress</code>
       for compress'd files, and <code>x-gzip</code> for gzip'd
       files. The <code>x-</code> prefix is ignored for encoding
       comparisons.</dd>

       <dt>Content-Language:</dt>

       <dd>The language of the variant, as an Internet standard
       language tag (RFC 1766). An example is <code>en</code>,
       meaning English.</dd>

       <dt>Content-Length:</dt>

       <dd>The length of the file, in bytes. If this header is not
       present, then the actual length of the file is used.</dd>

       <dt>Content-Type:</dt>

       <dd>
         The MIME media type of the document, with optional
         parameters. Parameters are separated from the media type
         and from one another by a semi-colon, with a syntax of
         <code>name=value</code>. Common parameters include:

         <dl>
           <dt>level</dt>

           <dd>an integer specifying the version of the media type.
           For <code>text/html</code> this defaults to 2, otherwise
           0.</dd>

           <dt>qs</dt>

           <dd>a floating-point number with a value in the range 0.0
           to 1.0, indicating the relative 'quality' of this variant
           compared to the other available variants, independent of
           the client's capabilities. For example, a jpeg file is
           usually of higher source quality than an ascii file if it
           is attempting to represent a photograph. However, if the
           resource being represented is ascii art, then an ascii
           file would have a higher source quality than a jpeg file.
           All qs values are therefore specific to a given
           resource.</dd>
         </dl>
         Example:

         <blockquote>
           <code>Content-Type: image/jpeg; qs=0.8</code>
         </blockquote>
       </dd>

       <dt>URI:</dt>

       <dd>The path to the file containing this variant, relative to
       the map file.</dd>
     </dl>

     <h2>MultiViews</h2>
     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.
     <hr />

     <h2><a id="cachenegotiateddocs"
     name="cachenegotiateddocs">CacheNegotiatedDocs</a>
     directive</h2>
     <a href="directive-dict.html#Syntax"
     rel="Help"><strong>Syntax:</strong></a>
     CacheNegotiatedDocs<br />
      <a href="directive-dict.html#Context"
     rel="Help"><strong>Context:</strong></a> server config<br />
      <a href="directive-dict.html#Status"
     rel="Help"><strong>Status:</strong></a> Base<br />
      <a href="directive-dict.html#Module"
     rel="Help"><strong>Module:</strong></a> mod_negotiation<br />
      <a href="directive-dict.html#Compatibility"
     rel="Help"><strong>Compatibility:</strong></a>
     CacheNegotiatedDocs is only available in Apache 1.1 and later.

     <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>

     <p>This directive only applies to requests which come from
     HTTP/1.0 browsers. HTTP/1.1 provides much better control over
     the caching of negotiated documents, and this directive has no
     effect in responses to HTTP/1.1 requests.</p>
     <hr />

     <h2><a id="languagepriority"
     name="languagepriority">LanguagePriority</a> directive</h2>
     <!--%plaintext &lt;?INDEX {\tt LanguagePriority} directive&gt; -->
     <a href="directive-dict.html#Syntax"
     rel="Help"><strong>Syntax:</strong></a> LanguagePriority
     <em>MIME-lang</em> [<em>MIME-lang</em>] ...<br />
      <a href="directive-dict.html#Context"
     rel="Help"><strong>Context:</strong></a> server config, virtual
     host, directory, .htaccess<br />
      <a href="directive-dict.html#Override"
     rel="Help"><strong>Override:</strong></a> FileInfo<br />
      <a href="directive-dict.html#Status"
     rel="Help"><strong>Status:</strong></a> Base<br />
      <a href="directive-dict.html#Module"
     rel="Help"><strong>Module:</strong></a> 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:</p>

     <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>Note that this directive only has an effect if a 'best'
     language cannot be determined by any other means. Correctly
     implemented HTTP/1.1 requests will mean this directive has no
     effect.</p>

     <p><strong>See also</strong>: <a
     href="./mod_mime.html#defaultlanguage">DefaultLanguage</a> and
     <a href="./mod_mime.html#addlanguage">AddLanguage</a>
     <!--#include virtual="footer.html" -->
     </p>
   </body>
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	<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
	<meta name="generator" content="HTML Tidy, see www.w3.org" />

	<title>Apache module mod_negotiation</title>
	</head>
	<!-- Background white, links blue (unvisited), navy (visited), red (active) -->

	<body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
	vlink="#000080" alink="#FF0000">
	<!--#include virtual="header.html" -->

	<h1 align="CENTER">Module mod_negotiation</h1>

	<p>This module provides for <a
	href="../content-negotiation.html">content negotiation</a>.</p>

	<p><a href="module-dict.html#Status"
	rel="Help"><strong>Status:</strong></a> Base<br />
	<a href="module-dict.html#SourceFile"
	rel="Help"><strong>Source File:</strong></a>
	mod_negotiation.c<br />
	<a href="module-dict.html#ModuleIdentifier"
	rel="Help"><strong>Module Identifier:</strong></a>
	negotiation_module</p>

	<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 handler
	<code>type-map</code>) which explicitly lists the files
	containing the variants.</li>

	<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.</li>
	</ul>

	<h2>Directives</h2>

	<ul>
	<li><a
	href="#cachenegotiateddocs">CacheNegotiatedDocs</a></li>

	<li><a href="#languagepriority">LanguagePriority</a></li>
	</ul>
	<strong>See also</strong>: <a
	href="./mod_mime.html#defaultlanguage">DefaultLanguage</a>, <a
	href="./mod_mime.html#addencoding">AddEncoding</a>, <a
	href="./mod_mime.html#addlanguage">AddLanguage</a>, <a
	href="./mod_mime.html#addtype">AddType</a>, and <a
	href="core.html#options">Options</a>.

	<h2>Type maps</h2>
	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:</dt>

	<dd>The encoding of the file. Apache only recognizes
	encodings that are defined by an <a
	href="mod_mime.html#addencoding">AddEncoding</a> directive.
	This normally includes the encodings <code>x-compress</code>
	for compress'd files, and <code>x-gzip</code> for gzip'd
	files. The <code>x-</code> prefix is ignored for encoding
	comparisons.</dd>

	<dt>Content-Language:</dt>

	<dd>The language of the variant, as an Internet standard
	language tag (RFC 1766). An example is <code>en</code>,
	meaning English.</dd>

	<dt>Content-Length:</dt>

	<dd>The length of the file, in bytes. If this header is not
	present, then the actual length of the file is used.</dd>

	<dt>Content-Type:</dt>

	<dd>
	The MIME media type of the document, with optional
	parameters. Parameters are separated from the media type
	and from one another by a semi-colon, with a syntax of
	<code>name=value</code>. Common parameters include:

	<dl>
	<dt>level</dt>

	<dd>an integer specifying the version of the media type.
	For <code>text/html</code> this defaults to 2, otherwise
	0.</dd>

	<dt>qs</dt>

	<dd>a floating-point number with a value in the range 0.0
	to 1.0, indicating the relative 'quality' of this variant
	compared to the other available variants, independent of
	the client's capabilities. For example, a jpeg file is
	usually of higher source quality than an ascii file if it
	is attempting to represent a photograph. However, if the
	resource being represented is ascii art, then an ascii
	file would have a higher source quality than a jpeg file.
	All qs values are therefore specific to a given
	resource.</dd>
	</dl>
	Example:

	<blockquote>
	<code>Content-Type: image/jpeg; qs=0.8</code>
	</blockquote>
	</dd>

	<dt>URI:</dt>

	<dd>The path to the file containing this variant, relative to
	the map file.</dd>
	</dl>

	<h2>MultiViews</h2>
	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.
	<hr />

	<h2><a id="cachenegotiateddocs"
	name="cachenegotiateddocs">CacheNegotiatedDocs</a>
	directive</h2>
	<a href="directive-dict.html#Syntax"
	rel="Help"><strong>Syntax:</strong></a>
	CacheNegotiatedDocs<br />
	<a href="directive-dict.html#Context"
	rel="Help"><strong>Context:</strong></a> server config<br />
	<a href="directive-dict.html#Status"
	rel="Help"><strong>Status:</strong></a> Base<br />
	<a href="directive-dict.html#Module"
	rel="Help"><strong>Module:</strong></a> mod_negotiation<br />
	<a href="directive-dict.html#Compatibility"
	rel="Help"><strong>Compatibility:</strong></a>
	CacheNegotiatedDocs is only available in Apache 1.1 and later.

	<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>

	<p>This directive only applies to requests which come from
	HTTP/1.0 browsers. HTTP/1.1 provides much better control over
	the caching of negotiated documents, and this directive has no
	effect in responses to HTTP/1.1 requests.</p>
	<hr />

	<h2><a id="languagepriority"
	name="languagepriority">LanguagePriority</a> directive</h2>
	<!--%plaintext <?INDEX {\tt LanguagePriority} directive> -->
	<a href="directive-dict.html#Syntax"
	rel="Help"><strong>Syntax:</strong></a> LanguagePriority
	<em>MIME-lang</em> [<em>MIME-lang</em>] ...<br />
	<a href="directive-dict.html#Context"
	rel="Help"><strong>Context:</strong></a> server config, virtual
	host, directory, .htaccess<br />
	<a href="directive-dict.html#Override"
	rel="Help"><strong>Override:</strong></a> FileInfo<br />
	<a href="directive-dict.html#Status"
	rel="Help"><strong>Status:</strong></a> Base<br />
	<a href="directive-dict.html#Module"
	rel="Help"><strong>Module:</strong></a> 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:</p>

	<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>Note that this directive only has an effect if a 'best'
	language cannot be determined by any other means. Correctly
	implemented HTTP/1.1 requests will mean this directive has no
	effect.</p>

	<p><strong>See also</strong>: <a
	href="./mod_mime.html#defaultlanguage">DefaultLanguage</a> and
	<a href="./mod_mime.html#addlanguage">AddLanguage</a>
	<!--#include virtual="footer.html" -->
	</p>
	</body>
	</html>