Redmine

I was wondering if there already exists some "Wiki book" concept implemented in some wiki dedicated software?

Not only to maintain a structure of pages, but also for their translation and versioning/tagging.

There is a plugin for Redmine called something like "wiki book" in fact, but it's function is to add another layer, a "book" object that stores an ordered list of wiki pages from the project, rather than actually modifying the stored inheritance for the wiki pages themselves.

It would certainly be helpful to support "this translation is out of date" versioning, particularly if changelogs could be compared and the translator see the specific language in the base page that has been changed. Or, further, that the reader could be notified visually when a paragraph is out-of-date, even, by Redmine calling the most-recent German version, for instance, then diffing it against the newest version of the base page, and indicating those passages that have been modified.

Actually, that would probably break with formatting changes, reorganization, etc, so not the best idea. But still indicating that a page were out of date could be helpful.