Semantics of a Foundational Subset for Executable UML Models

There are three conformance levels defined for fUML, corresponding to UML conformance levels L1, L2, and L3 (actually called “compliance levels” in the UML 2 Superstructure Specification). As in the UML 2 Superstructure, each conformance level is formally defined by merging the packages corresponding to the language units included at that level. However, for fUML, there are actually two sets of merges: one merge of the abstract syntax packages into a merged syntactic package for the level and a parallel merge of the corresponding execution model packages into a merged semantic package for the level. The merged syntactic package is a strict subset of the merged package for the corresponding UML 2 Superstructure level in the following sense: if the fUML syntactic Ln package is merged into the UML 2 Superstructure Ln package, the UML 2 Superstructure package is left unchanged.

The goal is to be able to syntactically interchange fUML models simply as UML 2 Superstructure models at the corresponding conformance level. Therefore, no new overall namespace is formally defined for fUML. The fUML abstract syntax is simply that portion of the UML 2 abstract syntax for which a corresponding semantic specification has been provided in this specification. To have a semantic meaning under this specification, a conforming fUML model must be constructed from the restricted portion of the UML abstract syntax defined for fUML, but it is otherwise interchanged as any other UML model.