6.3. Language Negotiation
The same useful functionality also applies to language. To demonstrate this we need to make up .html scripts in different languages. Well, we won't bother with real different languages; we'll just edit the scripts to say, for example:
and edit the English version so that it includes a new line:
Then we give each file an appropriate extension:
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. This is true of files in general, but it's necessary to be aware of some index subtleties. 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:
to make Apache look for a file called index.<something> rather than the default index.html.<something>.
Anyway, to give Apache the idea, we have to have the corresponding lines in the httpd.conf file:
AddLanguage it .it AddLanguage en .en AddLanguage ko .ko
Now our browser behaves in a rather civilized way. If you run ./go on the server, go to the client machine, and (in Netscape) go to Edit→Preferences→Languages and set Italian to be first, you see the Italian version of the index. If you change to English and reload, you get the English version. It you then go to catalog_summer, you see the pictures even though we didn't strictly specify the filenames. In a small way...magic!
Apache controls language selection if the browser doesn't. If you turn language preference off in your browser and edit the Config file to insert the line:
LanguagePriority it en
the browser will get Italian.
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 existed, 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. Correctly implemented HTTP/1.1 requests will mean that this directive has no effect.
How does this all work? Hark back to the environment variables in Chapter 4, "Common Gateway Interface (CGI) ". Among them were the following:
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