Registry Language Fallback
Multilingual Exchange store applications match the content of the HTTP_ACCEPT_LANGUAGE header with the form registration to determine which Exchange Web form to return to the browser. The browser sends the HTTP_ACCEPT_LANGUAGE header when it makes a request. The Language Preference dialog box in Internet Explorer allows users to select languages and to identify language preferences. The HTTP_ACCEPT_LANGUAGE header reflects the language preferences of the user. When more than one language is selected, each language is ranked and the ranking determines the language version selection of an Exchange Web form.
The following code sample shows how these language preferences appear in the HTTP_ACCEPT_LANGUAGE header.
GET / HTTP/1.1 Host: server Accept-Language: en-us,ja;q=0.8,fr;q=0.5,de;q=0.3
Quality, or q=, is a fraction, ranging from 0 to 1, with 1 being preferred. When a value does not have a quality rating, it is considered to be 1. In this example, en-us has the highest weight, followed by ja, fr, and de. A language from the header matches a value in a language property in a form registration if it exactly equals the property value. It is also a match when the value in the language property matches the prefix of the language in the header. The prefix is the characters that appear before the - in a language identifier. For example, en is the prefix for en-us.
If a form registration exists where the value of the language property is en, then it would be a match for this request. However a form registration with the value of the language property set to en-us would have a higher rank and would be preferred over the one that specified en. When none of the HTTP_ACCEPT_LANGUAGE header language preferences can be matched exactly, or by prefix, the form registration with a wildcard (*) language token is used. If the HTTP_ACCEPT_LANGUAGE header contains no language preference, the form registration with a wildcard (*) language token is also used.
The HTTP_ACCEPT_LANGUAGE header can contain more than one language preference that is an exact match in a form registration. When this occurs, the form registration for the language match that has the highest ranking in the HTTP_ACCEPT_LANGUAGE header is used.