Probably the best and most comprehensive metamodel covering all of the aspects and details of a relational database instance is the one found in the Eclipse Project docs. The model is based on SQL-92, is MOF2 compliant and is “capable of representing all non-syntactic aspects of SQL92 Data Definition Language (at the ‘intermediate’ conformance level)”. The model is submitted by IBM as part of forthcoming OMG IMM specification. IMM (Information Management Metamodel) is the new moniker for CWM (Commaon Warehouse Metamodel) as the ‘Warehouse’ word was not digestable for some and replaces the long due CWM 2.0.

MMX Framework provides full implementation of the model as defined in OMG specs. It includes 80 classes (both abstract and concrete). One open issue is the form of a URI reference used to link back to a relational database object. There is no common agreement on this; actually a W3C incubator group W3C RDB2RDF XG is just about to release a recommendation that should cover this topic as well.