It is interesting, I have been thinking about Divan DB for a long time now, and tonight I decided to give it some love and finally try to see exactly how hard it is going to be to write it.
It turns out that it isn’t really hard at all. You can see my progress here (http://github.com/ayende/rhino-divandb/tree/master). It now supports adding and retrieving documents, defining views, view caching, and (very simple) view application.
So you can now push a bunch of views and documents to the database and get the result back. There is a lot more to do (for example, handling edits with the views), but it seems to be fairly straight forward so far.