The UML4MDA team started late in the OMG-UML2 infrastructure process to define a core for a family of languages. For various reasons this was not pursued. However, the UML4MDA work represents a good starting point for the Semantic Core and is referenced here as our current baseline. While UML4MDA is referenced as the current baseline it is recognized that the Ontological languages are not sufficiently integrated and much more work needs to be done. It is very possible that the final semantic core will look very different from UML4MDA.