Rickard! Long time no see in the db4o forums! Did you take a look into db4o native queries? You get the most awesome query language possible: plain Java.100% typesafe100% compile-time checked100% object-oriented100% refactorableanalyzed and optimized to use database indexes=> 100% awesome :-)
Well, what I like about RDF which I haven't seen in any other approach to data storage or querying is that I don't have to know so much about the underlying models, and also that the database can add a ton of additional information on the fly for me.
For example, if I add the RDF tuple "B hasChild C" then the RDFDB can automatically add "C isChildOf B". "isChildOf" is a specialization of "isDescendantOf" so "C isDescendantof B" is also added. Then, since "isDescendantOf" is transitive and "B isDescendantOf A" was already in the database "C isDescendantOf A" is also added.
The result is that by adding the information "B hasChild C" I can now ask the database for all tuples matching "? isDescendantOf A" and get C as a result. That's just pure frickin' querying power in my book. Can you do things like that in db4o? Or in an SQL-database either, for that matter?