A Unified Superstructure for UML

A key aspect of successfully using UML is understanding the semantics of the notations. UML 2 will increase the already substantial collection of notations supported by UML 1.x. At the same time, this will augment the difficulty users experience in understanding semantics. In this paper we propose that while the diverse notations may render concepts differently, the concepts can often be considered semantically equivalent. This gives rise to an architecture where two single abstract syntaxes (structure and behaviour) underpin UML 2’s seven concrete syntax. Because there a fewer semantically distinct concepts, this makes UML both easier to understand and substantially easier to implement.