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 <H1 ALIGN="CENTER">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>.

 <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> 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. 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.
 <DT>Content-Language:
 <DD>The language of the variant, as an Internet standard language tag
 (RFC 1766).  An example is <CODE>en</CODE>, meaning English.
 <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 a
 semi-colon, with a syntax of <CODE>name=value</CODE>. Common parameters
 include:
 <DL>
 <DT>level
 <DD>an integer specifying the version of the media type.
 For <CODE>text/html</CODE> this defaults to 2, otherwise 0.
 <DT>qs
 <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.
 </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>


 <H2>Directives</H2>
 <UL>
 <LI><A HREF="#cachenegotiateddocs">CacheNegotiatedDocs</A>
 <LI><A HREF="#languagepriority">LanguagePriority</A>
 </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">Option</A>.

 <HR>


 <H2><A NAME="cachenegotiateddocs">CacheNegotiatedDocs</A></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>

 <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>

 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.


 <H2><A NAME="languagepriority">LanguagePriority</A></H2>
 <!--%plaintext &lt;?INDEX {\tt LanguagePriority} directive&gt; -->
 <A
  HREF="directive-dict.html#Syntax"
  REL="Help"
 ><STRONG>Syntax:</STRONG></A> LanguagePriority <EM>MIME-lang 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:

 <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>

 <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>

 <STRONG>See also</STRONG>:
 <A HREF="./mod_mime.html#defaultlanguage">DefaultLanguage</A> and
 <A HREF="./mod_mime.html#addlanguage">AddLanguage</A>


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	<HTML>
	<HEAD>
	<TITLE>Apache module mod_negotiation</TITLE>
	</HEAD>

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	<!--#include virtual="header.html" -->
	<H1 ALIGN="CENTER">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>.

	<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> 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. 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.
	<DT>Content-Language:
	<DD>The language of the variant, as an Internet standard language tag
	(RFC 1766). An example is <CODE>en</CODE>, meaning English.
	<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 a
	semi-colon, with a syntax of <CODE>name=value</CODE>. Common parameters
	include:
	<DL>
	<DT>level
	<DD>an integer specifying the version of the media type.
	For <CODE>text/html</CODE> this defaults to 2, otherwise 0.
	<DT>qs
	<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.
	</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>



	<H2>Directives</H2>
	<UL>
	<LI><A HREF="#cachenegotiateddocs">CacheNegotiatedDocs</A>
	<LI><A HREF="#languagepriority">LanguagePriority</A>
	</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">Option</A>.

	<HR>


	<H2><A NAME="cachenegotiateddocs">CacheNegotiatedDocs</A></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>

	<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>

	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.



	<H2><A NAME="languagepriority">LanguagePriority</A></H2>
	<!--%plaintext <?INDEX {\tt LanguagePriority} directive> -->
	<A
	HREF="directive-dict.html#Syntax"
	REL="Help"
	><STRONG>Syntax:</STRONG></A> LanguagePriority <EM>MIME-lang 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:

	<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>

	<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>

	<STRONG>See also</STRONG>:
	<A HREF="./mod_mime.html#defaultlanguage">DefaultLanguage</A> and
	<A HREF="./mod_mime.html#addlanguage">AddLanguage</A>


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