I searched some UML diagram on JPA, Hibernate, toplink, openJPA and EJB3 to get a quick understanding on how they are related to each other. I think that I have a good understanding now, but I found some confusing comparisons along the way.
The best I have found so far is : Java Persistence, implementations, and Java EE servers.
So I bring my own here, take it as a work in progress, open to criticisms :
I think that I will add the servers deployment view.
So here is the version 2, a bit more cluttered :