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Serving Documents
Based on Language Preference
Featured: July 1998
The Apache Web Server has the ability to look at the language preference
specified by a browser client and return the content of different files
depending on that preference. This ability, termed "language content negotiation",
is a simple yet very powerful feature of the Apache server that is not often
used.
There are essentially two approaches to content negotiation. The first
uses a "variants" file (or a "var" file) which essentially lists document
resources file by file and identifies them with a specific language. This
may be convenient for small sites or if you only want to provide language
typing for an entry page of a web site (which would then explicitly link
to web content authored in different languages). The second approach uses
file extensions (just like MIME types) to associate a file with a language.
Please find below a list of the steps necessary to configure the web services
on your Virtual Server to perform language content negotiation by file extension.
More information about configuring language content negotiation on a file
by file basis can be found by reading the reference documents included at
the bottom of this page.
- Add language type definitions to your srm.conf file
Using whatever method you find convenient, edit the file srm.conf
(located in your ~/www/conf
directory) and add language definitions using the AddLanguage
directive. For example, add the following lines to your
srm.conf file:
AddLanguage
en .en
AddLanguage es .es
AddLanguage fr .fr
AddLanguage de .de
AddLanguage it .it
AddLanguage jp .jp
Basically, this will associate the file extensions, .en .es .fr .de
.it .jp, with the corresponding language abbreviations, en es fr de
it and jp. The abbreviations are pre-defined and can be located in any
of the latest generations of browser clients. For example, in Netscape
4.x they are found in "Edit->Preferences->Navigator->Language->Add(button)".
In MSIE 4.x they are found in "View->Internet Options->General(tab)->Languages(button)->Add(button)".
- Add language priority definition to your srm.conf file
Using whatever method you find convenient, edit the file srm.conf
(located in your ~/www/conf
directory) and add a language priority definition using the
LanguagePriority directive. For example, add the following
line to your srm.conf
file:
LanguagePriority
en es fr de
The language priority directive allows you to give precedence to some
languages in case of a "tie" during content negotiation or if the browser
client does not specify a language priority (older browsers). Just list
the languages in decreasing order of preference.
- Modify the Options definition for your htdocs area to include
"MultiViews"
Using whatever method you find convenient, edit the file access.conf
(located in your ~/www/conf
directory) and add the MultiViews
option to the Options
directive that is part of your htdocs Directory
definition. For example, your Options line may look something like
this:
Options Indexes
FollowSymLinks MultiViews
The MultiViews
option can also be added to the Options
definition in .htaccess
files.
That's it! Now you will need to author content and upload it to your Virtual
Server using appropriate extensions. For example, you would create "index.html.en",
"index.html.es", "index.html.fr", etc. instead of an "index.html". When
the browser client requests "index.html", the server will analyze the language
preference of the browser client and serve the appropriate "index.html.*"
file seamlessly and transparently.
There is at least one snag. If the language preference the browser submits
does match any of the type definitions on your server and documents you
have authored. The server will return a 406 error (i.e. the resource was
found, but could not be delivered because the type of the resource is
incompatible with the acceptable types indicated by the accept
or accept-encoding
headers sent to the server by the client). So, for example, if a client
will only accept Greek content (el) and nothing else, but you have only
authored content in English, Spanish, and German, the client will receive
a 406 error. It may be wise to capture the 406 errors with a custom ErrorDocument
script.
References
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Apache: Web Server Directives Guidebook
Apache Server For Dummies