With domain-specific languages applied to software engineering, versioning becomes a whole new challenge. Steven Kelly has written a short note on versioning with their product which is questioned by Gareth.
Personally, I think that as long as the modeling part of the software development project needs to coexist with the more traditional, code-oriented part, we certainly need some kind of solution for versioning domain specific stuff together with the other stuff. Steven's approach may well be fine if the development is only done with the modeling tools.
Gareth puts it nicely: "I think it's fair to say that this is an area where our corner of the industry has a lot of work still to do."