It seems that simple validation (related to entity itself) is completely covered by Seam, except custom hibernate validators. AFAIK hibernate validator is supposed to work without hibernate itself, for instance it should work with Kodo. Complex validation (how entity correlates to the other entities, rules and policies) are not covered at all. Since Seam already employs JBoss Rules for authorization I believe it's possible to perform complex validation using Rules as well. The only thing I'm concerned about is performance. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4013827#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...