Joachim, I have never attmepted to do an instanceof with the inheritance type of a single table per hierarchy. Prehaps you should investigate some other strategies, namely table per subclass as i think this will provide you with the functionality you would like, like so: | //create query | Query tmpQuery = mEntityManager.createQuery("FROM Tag t"); | | //get query result | ArrayList<Tag> queryResult = (ArrayList<Tag>)tmpQuery.getResultList(); | | //get iterator | Iterator it = testList.iterator(); | | //loop | while (it.hasNext()) { | Tag element = (Tag) it.next(); | | if(element instanceof PlaceMark) { | //DO STUFF :-) | } | } | In your top level parent class you just need to annotate like so: @Inheritance(strategy = InheritanceType.JOINED) and i just have a getter and setter for the id in this parent class, and not in the sub-classes(children). All you should need to do in the children classes is just extend the parent class. To persist, just create and persist a child object and it automatically create and persists the parent objet with the correct attributes. Cheers, Andy View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3991643#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...