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| author |   hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 03:10:21 -0500 |
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| committer | hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 03:10:21 -0500 |
| commit | c0b7206652b2852bc574694e7ba07ba1c2acdc00 (patch) | |
| tree | 5cb95cb0e19e03610525903df46279df2c3b7eb1 /rubbos/app/apache2/manual/content-negotiation.html.en | |
| parent | b6d3d6e668b793220f2d3af1bc3e828553dc3fe6 (diff) | |
delete app
Change-Id: Id4c572809969ebe89e946e88063eaed262cff3f2
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
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diff --git a/rubbos/app/apache2/manual/content-negotiation.html.en b/rubbos/app/apache2/manual/content-negotiation.html.en deleted file mode 100644 index 89093c86..00000000 --- a/rubbos/app/apache2/manual/content-negotiation.html.en +++ /dev/null @@ -1,666 +0,0 @@ -<?xml version="1.0" encoding="ISO-8859-1"?> -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> -<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- - XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX - This file is generated from xml source: DO NOT EDIT - XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX - --> -<title>Content Negotiation - Apache HTTP Server</title> -<link href="./style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> -<link href="./style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> -<link href="./style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /> -<link href="./images/favicon.ico" rel="shortcut icon" /></head> -<body id="manual-page"><div id="page-header"> -<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> -<p class="apache">Apache HTTP Server Version 2.0</p> -<img alt="" src="./images/feather.gif" /></div> -<div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div> -<div id="path"> -<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Content Negotiation</h1> -<div class="toplang"> -<p><span>Available Languages: </span><a href="./en/content-negotiation.html" title="English"> en </a> | -<a href="./fr/content-negotiation.html" hreflang="fr" rel="alternate" title="Français"> fr </a> | -<a href="./ja/content-negotiation.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | -<a href="./ko/content-negotiation.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | -<a href="./tr/content-negotiation.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> -</div> - - - <p>Apache supports content negotiation as described in - the HTTP/1.1 specification. It can choose the best - representation of a resource based on the browser-supplied - preferences for media type, languages, character set and - encoding. It also implements a couple of features to give - more intelligent handling of requests from browsers that send - incomplete negotiation information.</p> - - <p>Content negotiation is provided by the - <code class="module"><a href="./mod/mod_negotiation.html">mod_negotiation</a></code> module, which is compiled in - by default.</p> -</div> -<div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#about">About Content Negotiation</a></li> -<li><img alt="" src="./images/down.gif" /> <a href="#negotiation">Negotiation in Apache</a></li> -<li><img alt="" src="./images/down.gif" /> <a href="#methods">The Negotiation Methods</a></li> -<li><img alt="" src="./images/down.gif" /> <a href="#better">Fiddling with Quality - Values</a></li> -<li><img alt="" src="./images/down.gif" /> <a href="#extensions">Extensions to Transparent Content -Negotiation</a></li> -<li><img alt="" src="./images/down.gif" /> <a href="#naming">Note on hyperlinks and naming conventions</a></li> -<li><img alt="" src="./images/down.gif" /> <a href="#caching">Note on Caching</a></li> -</ul></div> -<div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> -<div class="section"> -<h2><a name="about" id="about">About Content Negotiation</a></h2> - - <p>A resource may be available in several different - representations. For example, it might be available in - different languages or different media types, or a combination. - One way of selecting the most appropriate choice is to give the - user an index page, and let them select. However it is often - possible for the server to choose automatically. This works - because browsers can send, as part of each request, information - about what representations they prefer. For example, a browser - could indicate that it would like to see information in French, - if possible, else English will do. Browsers indicate their - preferences by headers in the request. To request only French - representations, the browser would send</p> - -<div class="example"><p><code>Accept-Language: fr</code></p></div> - - <p>Note that this preference will only be applied when there is - a choice of representations and they vary by language.</p> - - <p>As an example of a more complex request, this browser has - been configured to accept French and English, but prefer - French, and to accept various media types, preferring HTML over - plain text or other text types, and preferring GIF or JPEG over - other media types, but also allowing any other media type as a - last resort:</p> - -<div class="example"><p><code> - Accept-Language: fr; q=1.0, en; q=0.5<br /> - Accept: text/html; q=1.0, text/*; q=0.8, image/gif; q=0.6, image/jpeg; q=0.6, image/*; q=0.5, */*; q=0.1 -</code></p></div> - - <p>Apache supports 'server driven' content negotiation, as - defined in the HTTP/1.1 specification. It fully supports the - <code>Accept</code>, <code>Accept-Language</code>, - <code>Accept-Charset</code> and<code>Accept-Encoding</code> - request headers. Apache also supports 'transparent' - content negotiation, which is an experimental negotiation - protocol defined in RFC 2295 and RFC 2296. It does not offer - support for 'feature negotiation' as defined in these RFCs.</p> - - <p>A <strong>resource</strong> is a conceptual entity - identified by a URI (RFC 2396). An HTTP server like Apache - provides access to <strong>representations</strong> of the - resource(s) within its namespace, with each representation in - the form of a sequence of bytes with a defined media type, - character set, encoding, etc. Each resource may be associated - with zero, one, or more than one representation at any given - time. If multiple representations are available, the resource - is referred to as <strong>negotiable</strong> and each of its - representations is termed a <strong>variant</strong>. The ways - in which the variants for a negotiable resource vary are called - the <strong>dimensions</strong> of negotiation.</p> -</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> -<div class="section"> -<h2><a name="negotiation" id="negotiation">Negotiation in Apache</a></h2> - - <p>In order to negotiate a resource, the server needs to be - given information about each of the variants. This is done in - one of two ways:</p> - - <ul> - <li>Using a type map (<em>i.e.</em>, a <code>*.var</code> - file) which names the files containing the variants - explicitly, or</li> - - <li>Using a 'MultiViews' search, where the server does an - implicit filename pattern match and chooses from among the - results.</li> - </ul> - - <h3><a name="type-map" id="type-map">Using a type-map file</a></h3> - - <p>A type map is a document which is associated with the - handler named <code>type-map</code> (or, for - backwards-compatibility with older Apache configurations, the - MIME type <code>application/x-type-map</code>). Note that to - use this feature, you must have a handler set in the - configuration that defines a file suffix as - <code>type-map</code>; this is best done with</p> - -<div class="example"><p><code>AddHandler type-map .var</code></p></div> - - <p>in the server configuration file.</p> - - <p>Type map files should have the same name as the resource - which they are describing, and have an entry for each available - variant; these entries consist of contiguous HTTP-format header - lines. Entries for different variants are separated by blank - lines. Blank lines are illegal within an entry. It is - conventional to begin a map file with an entry for the combined - entity as a whole (although this is not required, and if - present will be ignored). An example map file is shown below. - This file would be named <code>foo.var</code>, as it describes - a resource named <code>foo</code>.</p> - -<div class="example"><p><code> - URI: foo<br /> -<br /> - URI: foo.en.html<br /> - Content-type: text/html<br /> - Content-language: en<br /> -<br /> - URI: foo.fr.de.html<br /> - Content-type: text/html;charset=iso-8859-2<br /> - Content-language: fr, de<br /> -</code></p></div> - <p>Note also that a typemap file will take precedence over the - filename's extension, even when Multiviews is on. If the - variants have different source qualities, that may be indicated - by the "qs" parameter to the media type, as in this picture - (available as JPEG, GIF, or ASCII-art): </p> - -<div class="example"><p><code> - URI: foo<br /> -<br /> - URI: foo.jpeg<br /> - Content-type: image/jpeg; qs=0.8<br /> -<br /> - URI: foo.gif<br /> - Content-type: image/gif; qs=0.5<br /> -<br /> - URI: foo.txt<br /> - Content-type: text/plain; qs=0.01<br /> -</code></p></div> - - <p>qs values can vary in the range 0.000 to 1.000. Note that - any variant with a qs value of 0.000 will never be chosen. - Variants with no 'qs' parameter value are given a qs factor of - 1.0. The qs parameter indicates 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 an original ASCII art, then an ASCII - representation would have a higher source quality than a JPEG - representation. A qs value is therefore specific to a given - variant depending on the nature of the resource it - represents.</p> - - <p>The full list of headers recognized is available in the <a href="mod/mod_negotiation.html#typemaps">mod_negotation - typemap</a> documentation.</p> - - -<h3><a name="multiviews" id="multiviews">Multiviews</a></h3> - - <p><code>MultiViews</code> is a per-directory option, meaning it - can be set with an <code class="directive"><a href="./mod/core.html#options">Options</a></code> - directive within a <code class="directive"><a href="./mod/core.html#directory"><Directory></a></code>, <code class="directive"><a href="./mod/core.html#location"><Location></a></code> or <code class="directive"><a href="./mod/core.html#files"><Files></a></code> section in - <code>httpd.conf</code>, or (if <code class="directive"><a href="./mod/core.html#allowoverride">AllowOverride</a></code> is properly set) in - <code>.htaccess</code> files. Note that <code>Options All</code> - does not set <code>MultiViews</code>; you have to ask for it by - name.</p> - - <p>The effect of <code>MultiViews</code> is as follows: if the - server receives a request for <code>/some/dir/foo</code>, if - <code>/some/dir</code> has <code>MultiViews</code> enabled, and - <code>/some/dir/foo</code> does <em>not</em> exist, then the - server reads the directory looking for files named foo.*, 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.</p> - - <p><code>MultiViews</code> may also apply to searches for the file - named by the <code class="directive"><a href="./mod/mod_dir.html#directoryindex">DirectoryIndex</a></code> directive, if the - server is trying to index a directory. If the configuration files - specify</p> -<div class="example"><p><code>DirectoryIndex index</code></p></div> - <p>then the server will arbitrate between <code>index.html</code> - and <code>index.html3</code> if both are present. If neither - are present, and <code>index.cgi</code> is there, the server - will run it.</p> - - <p>If one of the files found when reading the directory does not - have an extension recognized by <code>mod_mime</code> to designate - its Charset, Content-Type, Language, or Encoding, then the result - depends on the setting of the <code class="directive"><a href="./mod/mod_mime.html#multiviewsmatch">MultiViewsMatch</a></code> directive. This - directive determines whether handlers, filters, and other - extension types can participate in MultiViews negotiation.</p> - -</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> -<div class="section"> -<h2><a name="methods" id="methods">The Negotiation Methods</a></h2> - - <p>After Apache has obtained a list of the variants for a given - resource, either from a type-map file or from the filenames in - the directory, it invokes one of two methods to decide on the - 'best' variant to return, if any. It is not necessary to know - any of the details of how negotiation actually takes place in - order to use Apache's content negotiation features. However the - rest of this document explains the methods used for those - interested. </p> - - <p>There are two negotiation methods:</p> - - <ol> - <li><strong>Server driven negotiation with the Apache - algorithm</strong> is used in the normal case. The Apache - algorithm is explained in more detail below. When this - algorithm is used, Apache can sometimes 'fiddle' the quality - factor of a particular dimension to achieve a better result. - The ways Apache can fiddle quality factors is explained in - more detail below.</li> - - <li><strong>Transparent content negotiation</strong> is used - when the browser specifically requests this through the - mechanism defined in RFC 2295. This negotiation method gives - the browser full control over deciding on the 'best' variant, - the result is therefore dependent on the specific algorithms - used by the browser. As part of the transparent negotiation - process, the browser can ask Apache to run the 'remote - variant selection algorithm' defined in RFC 2296.</li> - </ol> - -<h3><a name="dimensions" id="dimensions">Dimensions of Negotiation</a></h3> - - <table> - - <tr valign="top"> - <th>Dimension</th> - - <th>Notes</th> - </tr> - - <tr valign="top"> - <td>Media Type</td> - - <td>Browser indicates preferences with the <code>Accept</code> - header field. Each item can have an associated quality factor. - Variant description can also have a quality factor (the "qs" - parameter).</td> - </tr> - - <tr valign="top"> - <td>Language</td> - - <td>Browser indicates preferences with the - <code>Accept-Language</code> header field. Each item can have - a quality factor. Variants can be associated with none, one or - more than one language.</td> - </tr> - - <tr valign="top"> - <td>Encoding</td> - - <td>Browser indicates preference with the - <code>Accept-Encoding</code> header field. Each item can have - a quality factor.</td> - </tr> - - <tr valign="top"> - <td>Charset</td> - - <td>Browser indicates preference with the - <code>Accept-Charset</code> header field. Each item can have a - quality factor. Variants can indicate a charset as a parameter - of the media type.</td> - </tr> - </table> - - -<h3><a name="algorithm" id="algorithm">Apache Negotiation Algorithm</a></h3> - - <p>Apache can use the following algorithm to select the 'best' - variant (if any) to return to the browser. This algorithm is - not further configurable. It operates as follows:</p> - - <ol> - <li>First, for each dimension of the negotiation, check the - appropriate <em>Accept*</em> header field and assign a - quality to each variant. If the <em>Accept*</em> header for - any dimension implies that this variant is not acceptable, - eliminate it. If no variants remain, go to step 4.</li> - - <li> - Select the 'best' variant by a process of elimination. Each - of the following tests is applied in order. Any variants - not selected at each test are eliminated. After each test, - if only one variant remains, select it as the best match - and proceed to step 3. If more than one variant remains, - move on to the next test. - - <ol> - <li>Multiply the quality factor from the <code>Accept</code> - header with the quality-of-source factor for this variants - media type, and select the variants with the highest - value.</li> - - <li>Select the variants with the highest language quality - factor.</li> - - <li>Select the variants with the best language match, - using either the order of languages in the - <code>Accept-Language</code> header (if present), or else - the order of languages in the <code>LanguagePriority</code> - directive (if present).</li> - - <li>Select the variants with the highest 'level' media - parameter (used to give the version of text/html media - types).</li> - - <li>Select variants with the best charset media - parameters, as given on the <code>Accept-Charset</code> - header line. Charset ISO-8859-1 is acceptable unless - explicitly excluded. Variants with a <code>text/*</code> - media type but not explicitly associated with a particular - charset are assumed to be in ISO-8859-1.</li> - - <li>Select those variants which have associated charset - media parameters that are <em>not</em> ISO-8859-1. If - there are no such variants, select all variants - instead.</li> - - <li>Select the variants with the best encoding. If there - are variants with an encoding that is acceptable to the - user-agent, select only these variants. Otherwise if - there is a mix of encoded and non-encoded variants, - select only the unencoded variants. If either all - variants are encoded or all variants are not encoded, - select all variants.</li> - - <li>Select the variants with the smallest content - length.</li> - - <li>Select the first variant of those remaining. This - will be either the first listed in the type-map file, or - when variants are read from the directory, the one whose - file name comes first when sorted using ASCII code - order.</li> - </ol> - </li> - - <li>The algorithm has now selected one 'best' variant, so - return it as the response. The HTTP response header - <code>Vary</code> is set to indicate the dimensions of - negotiation (browsers and caches can use this information when - caching the resource). End.</li> - - <li>To get here means no variant was selected (because none - are acceptable to the browser). Return a 406 status (meaning - "No acceptable representation") with a response body - consisting of an HTML document listing the available - variants. Also set the HTTP <code>Vary</code> header to - indicate the dimensions of variance.</li> - </ol> - -</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> -<div class="section"> -<h2><a name="better" id="better">Fiddling with Quality - Values</a></h2> - - <p>Apache sometimes changes the quality values from what would - be expected by a strict interpretation of the Apache - negotiation algorithm above. This is to get a better result - from the algorithm for browsers which do not send full or - accurate information. Some of the most popular browsers send - <code>Accept</code> header information which would otherwise - result in the selection of the wrong variant in many cases. If a - browser sends full and correct information these fiddles will not - be applied.</p> - -<h3><a name="wildcards" id="wildcards">Media Types and Wildcards</a></h3> - - <p>The <code>Accept:</code> request header indicates preferences - for media types. It can also include 'wildcard' media types, such - as "image/*" or "*/*" where the * matches any string. So a request - including:</p> - -<div class="example"><p><code>Accept: image/*, */*</code></p></div> - - <p>would indicate that any type starting "image/" is acceptable, - as is any other type. - Some browsers routinely send wildcards in addition to explicit - types they can handle. For example:</p> - -<div class="example"><p><code> - Accept: text/html, text/plain, image/gif, image/jpeg, */* -</code></p></div> - <p>The intention of this is to indicate that the explicitly listed - types are preferred, but if a different representation is - available, that is ok too. Using explicit quality values, - what the browser really wants is something like:</p> -<div class="example"><p><code> - Accept: text/html, text/plain, image/gif, image/jpeg, */*; q=0.01 -</code></p></div> - <p>The explicit types have no quality factor, so they default to a - preference of 1.0 (the highest). The wildcard */* is given a - low preference of 0.01, so other types will only be returned if - no variant matches an explicitly listed type.</p> - - <p>If the <code>Accept:</code> header contains <em>no</em> q - factors at all, Apache sets the q value of "*/*", if present, to - 0.01 to emulate the desired behavior. It also sets the q value of - wildcards of the format "type/*" to 0.02 (so these are preferred - over matches against "*/*". If any media type on the - <code>Accept:</code> header contains a q factor, these special - values are <em>not</em> applied, so requests from browsers which - send the explicit information to start with work as expected.</p> - - -<h3><a name="exceptions" id="exceptions">Language Negotiation Exceptions</a></h3> - - <p>New in Apache 2.0, some exceptions have been added to the - negotiation algorithm to allow graceful fallback when language - negotiation fails to find a match.</p> - - <p>When a client requests a page on your server, but the server - cannot find a single page that matches the - <code>Accept-language</code> sent by - the browser, the server will return either a "No Acceptable - Variant" or "Multiple Choices" response to the client. To avoid - these error messages, it is possible to configure Apache to ignore - the <code>Accept-language</code> in these cases and provide a - document that does not explicitly match the client's request. The - <code class="directive"><a href="./mod/mod_negotiation.html#forcelanguagepriority">ForceLanguagePriority</a></code> - directive can be used to override one or both of these error - messages and substitute the servers judgement in the form of the - <code class="directive"><a href="./mod/mod_negotiation.html#languagepriority">LanguagePriority</a></code> - directive.</p> - - <p>The server will also attempt to match language-subsets when no - other match can be found. For example, if a client requests - documents with the language <code>en-GB</code> for British - English, the server is not normally allowed by the HTTP/1.1 - standard to match that against a document that is marked as simply - <code>en</code>. (Note that it is almost surely a configuration - error to include <code>en-GB</code> and not <code>en</code> in the - <code>Accept-Language</code> header, since it is very unlikely - that a reader understands British English, but doesn't understand - English in general. Unfortunately, many current clients have - default configurations that resemble this.) However, if no other - language match is possible and the server is about to return a "No - Acceptable Variants" error or fallback to the <code class="directive"><a href="./mod/mod_negotiation.html#languagepriority">LanguagePriority</a></code>, the server - will ignore the subset specification and match <code>en-GB</code> - against <code>en</code> documents. Implicitly, Apache will add - the parent language to the client's acceptable language list with - a very low quality value. But note that if the client requests - "en-GB; q=0.9, fr; q=0.8", and the server has documents - designated "en" and "fr", then the "fr" document will be returned. - This is necessary to maintain compliance with the HTTP/1.1 - specification and to work effectively with properly configured - clients.</p> - - <p>In order to support advanced techniques (such as cookies or - special URL-paths) to determine the user's preferred language, - since Apache 2.0.47 <code class="module"><a href="./mod/mod_negotiation.html">mod_negotiation</a></code> recognizes - the <a href="env.html">environment variable</a> - <code>prefer-language</code>. If it exists and contains an - appropriate language tag, <code class="module"><a href="./mod/mod_negotiation.html">mod_negotiation</a></code> will - try to select a matching variant. If there's no such variant, - the normal negotiation process applies.</p> - - <div class="example"><h3>Example</h3><p><code> - SetEnvIf Cookie "language=en" prefer-language=en<br /> - SetEnvIf Cookie "language=fr" prefer-language=fr - </code></p></div> - -</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> -<div class="section"> -<h2><a name="extensions" id="extensions">Extensions to Transparent Content -Negotiation</a></h2> - -<p>Apache extends the transparent content negotiation protocol (RFC -2295) as follows. A new <code>{encoding ..}</code> element is used in -variant lists to label variants which are available with a specific -content-encoding only. The implementation of the RVSA/1.0 algorithm -(RFC 2296) is extended to recognize encoded variants in the list, and -to use them as candidate variants whenever their encodings are -acceptable according to the <code>Accept-Encoding</code> request -header. The RVSA/1.0 implementation does not round computed quality -factors to 5 decimal places before choosing the best variant.</p> -</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> -<div class="section"> -<h2><a name="naming" id="naming">Note on hyperlinks and naming conventions</a></h2> - - <p>If you are using language negotiation you can choose between - different naming conventions, because files can have more than - one extension, and the order of the extensions is normally - irrelevant (see the <a href="mod/mod_mime.html#multipleext">mod_mime</a> documentation - for details).</p> - - <p>A typical file has a MIME-type extension (<em>e.g.</em>, - <code>html</code>), maybe an encoding extension (<em>e.g.</em>, - <code>gz</code>), and of course a language extension - (<em>e.g.</em>, <code>en</code>) when we have different - language variants of this file.</p> - - <p>Examples:</p> - - <ul> - <li>foo.en.html</li> - - <li>foo.html.en</li> - - <li>foo.en.html.gz</li> - </ul> - - <p>Here some more examples of filenames together with valid and - invalid hyperlinks:</p> - - <table class="bordered"> - - <tr> - <th>Filename</th> - - <th>Valid hyperlink</th> - - <th>Invalid hyperlink</th> - </tr> - - <tr> - <td><em>foo.html.en</em></td> - - <td>foo<br /> - foo.html</td> - - <td>-</td> - </tr> - - <tr> - <td><em>foo.en.html</em></td> - - <td>foo</td> - - <td>foo.html</td> - </tr> - - <tr> - <td><em>foo.html.en.gz</em></td> - - <td>foo<br /> - foo.html</td> - - <td>foo.gz<br /> - foo.html.gz</td> - </tr> - - <tr> - <td><em>foo.en.html.gz</em></td> - - <td>foo</td> - - <td>foo.html<br /> - foo.html.gz<br /> - foo.gz</td> - </tr> - - <tr> - <td><em>foo.gz.html.en</em></td> - - <td>foo<br /> - foo.gz<br /> - foo.gz.html</td> - - <td>foo.html</td> - </tr> - - <tr> - <td><em>foo.html.gz.en</em></td> - - <td>foo<br /> - foo.html<br /> - foo.html.gz</td> - - <td>foo.gz</td> - </tr> - </table> - - <p>Looking at the table above, you will notice that it is always - possible to use the name without any extensions in a hyperlink - (<em>e.g.</em>, <code>foo</code>). The advantage is that you - can hide the actual type of a document rsp. file and can change - it later, <em>e.g.</em>, from <code>html</code> to - <code>shtml</code> or <code>cgi</code> without changing any - hyperlink references.</p> - - <p>If you want to continue to use a MIME-type in your - hyperlinks (<em>e.g.</em> <code>foo.html</code>) the language - extension (including an encoding extension if there is one) - must be on the right hand side of the MIME-type extension - (<em>e.g.</em>, <code>foo.html.en</code>).</p> -</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> -<div class="section"> -<h2><a name="caching" id="caching">Note on Caching</a></h2> - - <p>When a cache stores a representation, it associates it with - the request URL. The next time that URL is requested, the cache - can use the stored representation. But, if the resource is - negotiable at the server, this might result in only the first - requested variant being cached and subsequent cache hits might - return the wrong response. To prevent this, Apache normally - marks all responses that are returned after content negotiation - as non-cacheable by HTTP/1.0 clients. Apache also supports the - HTTP/1.1 protocol features to allow caching of negotiated - responses.</p> - - <p>For requests which come from a HTTP/1.0 compliant client - (either a browser or a cache), the directive <code class="directive"><a href="./mod/mod_negotiation.html#cachenegotiateddocs">CacheNegotiatedDocs</a></code> can be - used to allow caching of responses which were subject to - negotiation. This directive can be given in the server config or - virtual host, and takes no arguments. It has no effect on requests - from HTTP/1.1 clients.</p> -</div></div> -<div class="bottomlang"> -<p><span>Available Languages: </span><a href="./en/content-negotiation.html" title="English"> en </a> | -<a href="./fr/content-negotiation.html" hreflang="fr" rel="alternate" title="Français"> fr </a> | -<a href="./ja/content-negotiation.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | -<a href="./ko/content-negotiation.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | -<a href="./tr/content-negotiation.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> -</div><div id="footer"> -<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> -<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> -</body></html>
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