There are two reasons why I didn't address OODBMSes

And you're perfectly right. For now OODBMSes are still more than ever small exotic things compared to mastodontic RDBMSes (commercial rules applies...).

In fact, I always found RDBMSes complex and difficult stuff, even a bit archaic (the gap from sequential-indexed files is not so wide).

Here's some interesting reference about OODBMSes:

• Object Oriented Databases
• Object-Relational Database Management System