Language Negotiation (Apache: The Definitive Guide, 3rd Edition)

6.3. Language Negotiation

<h1>Italian Version</h1>

and edit the English version so that it includes a new line:

<h1>English Version</h1>

Then we give each file an appropriate extension:

index.html.en for English
index.html.it for Italian
index.html.ko for Korean

Apache recognizes language variants: en-US is seen as a version of general English, en, which seems reasonable. You can also offer documents that serve more than one language. If you had a "franglais" version, you could serve it to both English speakers and Francophones by naming it frangdoc.en.fr. Of course, in real life you would have to go to substantially more trouble, what with translators and special keyboards and all. Also, the Italian version of the index would need to point to Italian versions of the catalogs. But in the fantasy world of Butterthlies, Inc., it's all so simple.

The Italian version of our index would be index.html.it. By default, Apache looks for a file called index.html.<something>. If it has a language extension, like index.html.it, it will find the index file, happily add the language extension, and then serve up what the browser prefers. If, however, you call the index file index.it.html, Apache will still look for, and fail to find, index.html.<something>. If index.html.en is present, that will be served up. If index.en.html is there, then Apache gives up and serves up a list of all the files. The moral is, if you want to deal with index filenames in either order — index.it.html alongside index.html.en — you need the directive:

DirectoryIndex index

to make Apache look for a file called index.<something> rather than the default index.html.<something>.

To give Apache the idea, we need the corresponding lines in the httpd1.conf file:

AddLanguage it .it
AddLanguage en .en
AddLanguage ko .ko

Apache controls language selection if the browser doesn't. If you turn language preference off in your browser, edit the Config file (httpd2.conf ) to insert the line:

LanguagePriority it en ko

stop Apache and restart with ./go 2, the browser will get Italian.

LanguagePriority

LanguagePriority MIME-lang MIME-lang...
Server config, virtual host, directory, .htaccess

The LanguagePriority directive sets the precedence of language variants for the case in which the client does not express a preference when handling a multiviews request. The MIME-lang list is in order of decreasing preference. For example:

LanguagePriority en fr de

For a request for foo.html, where foo.html.fr and foo.html.de both exist but the browser did not express a language preference, foo.html.fr would be returned.

Note that this directive only has an effect if a "best" language cannot be determined by any other means. It will not work if there is a DefaultLanguage defined. Correctly implemented HTTP 1.1 requests will mean that this directive has no effect.

How does this all work? You can look ahead to the environment variables in Chapter 16. Among them were the following:

...
HTTP_ACCEPT=image/gif,image/x-bitmap,image/jpeg,image/pjpeg,*/*
...
HTTP_ACCEPT_LANGUAGE=it
...

Apache uses this information to work out what it can acceptably send back from the choices at its disposal.

AddLanguage

AddLanguage MIME-lang extension [extension] ...
Server config, virtual host, directory, .htaccess

The AddLanguage directive maps the given filename extension to the specified content language. MIME-lang is the MIME language of filenames containing extensions. This mapping is added to any already in force, overriding any mappings that already exist for the same extension. For example:

AddEncoding x-compress .Z
AddLanguage en .en
AddLanguage fr .fr

Then the document xxxx.en.Z will be treated as a compressed English document (as will the document xxxx.Z.en). Although the content language is reported to the client, the browser is unlikely to use this information. The AddLanguage directive is more useful for content negotiation, where the server returns one from several documents based on the client's language preference.

If multiple language assignments are made for the same extension, the last one encountered is the one that is used. That is, for the case of:

AddLanguage en .en
AddLanguage en-uk .en
AddLanguage en-us .en

documents with the extension .en would be treated as being en-us.

The extension argument is case insensitive and can be specified with or without a leading dot.

DefaultLanguage

DefaultLanguage MIME-lang
Server config, virtual host, directory, .htaccess
DefaultLanguage is only available in Apache 1.3.4 and later.

The DefaultLanguage directive tells Apache that all files in the directive's scope (e.g., all files covered by the current <Directory> container) that don't have an explicit language extension (such as .fr or .de as configured by AddLanguage) should be considered to be in the specified MIME-lang language. This allows entire directories to be marked as containing Dutch content, for instance, without having to rename each file. Note that unlike using extensions to specify languages, DefaultLanguage can only specify a single language.

If no DefaultLanguage directive is in force and a file does not have any language extensions as configured by AddLanguage, then that file will be considered to have no language attribute.

RemoveLanguage

RemoveLanguage extension [extension] ...
directory, .htaccess
RemoveLanguage is only available in Apache 2.0.24 and later.

The RemoveLanguage directive removes any language associations for files with the given extensions. This allows .htaccess files in subdirectories to undo any associations inherited from parent directories or the server config files.

The extension argument is case insensitive and can be specified with or without a leading dot.


6.2. Content Negotiation		6.4. Type Maps