The thing that I missed initially and that Emmanuel pointed out was the the spi for PersistentunitInfo done in fact imply that we can safely assume that returned urls are either jar files or directories. http://java.sun.com/javaee/5/docs/api/javax/persistence/spi/PersistenceUn... http://java.sun.com/javaee/5/docs/api/javax/persistence/spi/PersistenceUn... So i think this is more than just a question of working vs optimized. We also need to consider other JPA providers being plugged into JBoss AS right? You'd have to assume they would take this "implied spec" and run with it as well... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4109078#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...