[jboss-as7-dev] Deployment descriptors: XML schemas backward compatible ?

Hi JBoss Team, Sorry if this is not the right place to ask, but I had no luck in users list. I would like to know if JBoss's XML schemas and DTDs for deployment descriptors support backward compatibility, and if there are plans to keep backward compatibility in the future. Could someone confirm it or point me to a relevant document ? Thanks. -- Marian MULLER SERLI