Towards a Semantics of Activity Diagrams with Semantic Variation Points
  UML activity diagrams have become an established notation to model control and data ow on various levels of abstraction, ranging from fine-grained descriptions of algorithms to high-level workflow models in business applications. A formal semantics has to capture the flexibility of the interpretation of activity diagrams in real systems, which makes it inappropriate to define a fixed formal semantics. In this paper, we define a semantics with semantic variation points that allow for a customizable, application-specific interpretation of activity diagrams. We examine concrete variants of the activity diagram semantics which may also entail variants of the syntax re ecting the intended use at hand. 
Hans Gr\"onninger, Dirk Rei{\ss}, Bernhard Rumpe
cs.SE