Compositional Operational Semantics of a UML-Kernel-Model Language

It is important to have a formal semantics for the objectoriented modelling language UML. Furthermore, it would be fine to have a compositional semantics in order to model open distributed systems and component-based systems. For this reason we present a compositional operational semantics for the state machines associated to a class diagram. We first describe the meaning of objects, then the meaning of sets of objects that contain only one thread of control (these sets are called activity groups) and finally, we give the meaning how those activity groups interact with each other. All these semantics are given in terms of labelled transition systems.