If you want to serialize your objects in a format other than XMI, that can be arranged as well. You will need to supply your own serialization and parsing code. Create your own resource class (as a subclass of ResourceImpl) that implements your preferred serialization format, and then either register it locally with your resource set, or with the global factory registry if you want it to always be used with your model. from http://publib.boulder.ibm.com/infocenter/wasinfo/v6r0/index.jsp?topic=%2Forg.eclipse.emf.doc%2Freferences%2Foverview%2FEMF.html