fUML (Foundational UML) is a subset of the standard Unified Modeling Language (UML) that includes standard, precise execution semantics. This subset encompasses typical structural modeling constructs of UML such as classes, associations, data types, and enumerations, as well as the ability to model behavior using UML activities composed from a set of primitive actions. Therefore, a model constructed in fUML is executable in the same sense as a program in a traditional programming language, but with the level of abstraction and richness of expression of a modeling language2.