anonymous wrote : in the implementation. And then suppose that jPDL wants to add a property to all executions... then you end up in multiple inheritence. I understand. Extending implementation classes is indeed a no-go when the process instance implementation must be extendable. So how do you see the inheritance? | ProcessInstance (interface) extends Execution | ExecutionImpl implements ProcessInstance, Execution | -> This could lead to castings of executions to ProcessInstances, which aren't process instances (ie no root execution). But for the compiler, nothing is wrong since they are exactly the same... I don't know, I get a funy feeling about it when I think about it like that... This leads back to the question if processInstance == Execution? (I know we already discussed this, but perhaps I'm seeing this in the wrong perspective here) anonymous wrote : | and besides, i think it is best that all executions (incl process instances) are stored in only 1 single table. | Definitely View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4225884#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...