Thanks for your answers! I'll definitely read the article, hopefully the book too as time permits.
It is now clearer to me. JDO is a persistence framework that handles the "infamous" object-relational mapping issue. It is a (better in your opinion and experience) alternative to CMP and BMP with respect to persistence services.
So, JDO provides an OO abstaction of your underlying DB (typically a relational one, as abstracted - at a lower level - by
JDBC). Now the question is why JDO is better than any other of the host of OO-relational mapping solution that (may) exist outthere (Toplink, WebSphere Studio Data Access Beans, etc.)...
And returning to the EJB issue, session beans and message-driven beans are orthogonal to JDO, since the provide pretty much transactional and messaging services that are outside JDO's scope.
Do the above make sense?
Thanks,
Panagiotis.