I want to make a website that offers content in different languages (fairly common). On top of this most articles (books) are written in one or at most two languages. The user that is browsing the site in language X can see articles that are written in any language, but he should also be able to filter out those languages that he's not interested in.
Any tips on how to make this separation between site language and article language (specially the filtering part) clear to the user and not confuse him? The filtering is done on a global scale. So once the user selects "Only French+English articles" the whole site only displays those articles no matter if you're examining search results, categories etc. Therefore this global selection has to be visible and "updatable". Also the site language should always be visible.
Do you know of any examples where this has been done before?