"gsegura" wrote : And that is the problem because when more than one user are inserting CourseNotes to the collection, the second one will get an optimisticlockexception at the time he tries to merge his instance of the course I would just used managed entities at all times. anonymous wrote : At the same time this makes think of another issue: the implementation of master-detail editions, which at first, for the neophyte like me, feels natural to handle using nested conversations and sharing full objects but the preferred way to go is using entityhome and its passing-just-the-id technique, again a not very OO-ish way IMHO. I don't really understand this statement. Why can't you use EntityHome and nested conversations? EntityHome uses objects when inside the conversation (you just pass in the id to get started, probably from outside the conversation). Why is EntityHome not very ooish? JPA doesn't have a concept of read only entities afaik. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4113970#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...