depends on the setting of the <a
href="mod/mod_mime.html#multiviewsmatch">MultiViewsMatch</a>
directive. This directive determines whether handlers, filters,
- and other file types can participate in MultiViews
+ and other extension types can participate in MultiViews
negotiation.</p>
<h2>The Negotiation Methods</h2>
<h3>Language Negotiation Exceptions</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 Accept-language sent by
the browser, the server will return either a "No Acceptable
href="mod_negotiation.html#languagepriority">LanguagePriority</a>
directive.</p>
- <p>The <code>ForceLanguagePriority</code> directive also causes
- Apache to attempt to match language-subsets against their parent
- language when no other match can be obtained. 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 return a document that is marked as simply
+ <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
Accept-Language 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.) With the
- <code>ForceLanguagePriority</code> header, the server can be
- configured to ignore the subset specification and match
- <code>en-GB</code> against <code>en</code> documents. But note
- that if the client requests "en-GB; qs=0.9, fr; qs=0.8", and the
- server has documents designated "en" and "fr", then the "fr"
- document will be returned regardless of the
- <code>ForceLanguagePriority</code> directive. This is necessary
- to maintain compliance with the HTTP/1.1 specification.</p>
+ 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>LanguagePriority</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; qs=0.9, fr;
+ qs=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>
<h2>Extensions to Transparent Content Negotiation</h2>
depends on the setting of the <a
href="mod/mod_mime.html#multiviewsmatch">MultiViewsMatch</a>
directive. This directive determines whether handlers, filters,
- and other file types can participate in MultiViews
+ and other extension types can participate in MultiViews
negotiation.</p>
<h2>The Negotiation Methods</h2>
<h3>Language Negotiation Exceptions</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 Accept-language sent by
the browser, the server will return either a "No Acceptable
href="mod_negotiation.html#languagepriority">LanguagePriority</a>
directive.</p>
- <p>The <code>ForceLanguagePriority</code> directive also causes
- Apache to attempt to match language-subsets against their parent
- language when no other match can be obtained. 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 return a document that is marked as simply
+ <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
Accept-Language 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.) With the
- <code>ForceLanguagePriority</code> header, the server can be
- configured to ignore the subset specification and match
- <code>en-GB</code> against <code>en</code> documents. But note
- that if the client requests "en-GB; qs=0.9, fr; qs=0.8", and the
- server has documents designated "en" and "fr", then the "fr"
- document will be returned regardless of the
- <code>ForceLanguagePriority</code> directive. This is necessary
- to maintain compliance with the HTTP/1.1 specification.</p>
+ 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>LanguagePriority</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; qs=0.9, fr;
+ qs=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>
<h2>Extensions to Transparent Content Negotiation</h2>
argument; it was turned on by the presence of the directive by
itself.</p>
<hr/><h2><a name="ForceLanguagePriority">ForceLanguagePriority</a> <a name="forcelanguagepriority">Directive</a></h2><table cellpadding="1" cellspacing="0" border="0" bgcolor="#cccccc"><tr><td><table bgcolor="#ffffff"><tr><td nowrap="nowrap"><strong>Description: </strong></td><td>Action to take if a single acceptable document is not
-found</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Syntax" class="help">Syntax:</a></td><td>ForceLanguagePriority None|Prefer|Fallback [Prefer|Fallback]</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Default" class="help">Default:</a></td><td><code>ForceLanguagePriority
None</code></td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Context" class="help">Context:</a></td><td>server config, virtual host, directory, .htaccess</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Override" class="help">Override:</a></td><td>FileInfo</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Status" class="help">Status:</a></td><td>Base</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Module" class="help">Module:</a></td><td>mod_negotiation</td></tr><tr><td nowrap="nowrap" align="left" valign="top"><a href="directive-dict.html#Compatibility" class="help">Compatibility:</a></td><td>Available in version 2.0.30 and later</td></tr></table></td></tr></table>
+found</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Syntax" class="help">Syntax:</a></td><td>ForceLanguagePriority None|Prefer|Fallback [Prefer|Fallback]</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Default" class="help">Default:</a></td><td><code>ForceLanguagePriority
Prefer</code></td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Context" class="help">Context:</a></td><td>server config, virtual host, directory, .htaccess</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Override" class="help">Override:</a></td><td>FileInfo</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Status" class="help">Status:</a></td><td>Base</td></tr><tr><td nowrap="nowrap"><a href="directive-dict.html#Module" class="help">Module:</a></td><td>mod_negotiation</td></tr><tr><td nowrap="nowrap" align="left" valign="top"><a href="directive-dict.html#Compatibility" class="help">Compatibility:</a></td><td>Available in version 2.0.30 and later</td></tr></table></td></tr></table>
<p>The <code class="directive">ForceLanguagePriority</code> directive uses
the given <a href="#languagepriority" class="directive"><code class="directive">LanguagePriority</code></a> to satisfy
negotation where the server could otherwise not return a single
<description>Action to take if a single acceptable document is not
found</description>
<syntax>ForceLanguagePriority None|Prefer|Fallback [Prefer|Fallback]</syntax>
-<default>ForceLanguagePriority None</default>
+<default>ForceLanguagePriority Prefer</default>
<contextlist><context>server config</context>
<context>virtual host</context>
<context>directory</context>
projects / apache / commitdiff