Different worlds share the same races, but use different languages. For example Elves. Everybody who wants Elves in their world might create his own language, no matter if someone did it already. Tolkien created his own and I don't think he's the only one.
How should we handle this case in the tag system? Should we have generalized tags, ex elvish or more precise ones, ex tolkien-elvish? Maybe we should have both? Or should we use them with other tags, ex elvish together with tolkien?