Endogenous Metamodeling Semantics for Structural UML 2 Concepts

A lot of work has been done in order to put the Unified Modeling Language (UML) on a formal basis by translating concepts into various formal languages, e.g., set theory or graph transformation. While the abstract UML syntax is defined by using an endogenous approach, i. e., UML describes its abstract syntax using UML, this approach is rarely used for its semantics. This paper shows how to apply an endogenous approach called metamodeling semantics for central parts of the UML standard. To this end, we enrich existing UML language elements with constraints specified in the Object Constraint Language (OCL) in order to describe a semantic domain model. The UML specification explicitly states that complete runtime semantics is not included in the standard because it would be a major amount of work. However, we believe that certain central concepts, like the ones used in the UML standard and in particular property features as subsets, union and derived, need to be explicitly modeled to enforce a common understanding. Using such an endogenous approach enables the validation and verification of the UML standard by using off-the-shelf UML and OCL tools.