State Diagrams in Uml: a Formal Semantics Using Graph Transformations or Diagrams Are Nice, but Graphs Are worth Their Price

We show how to transform UML (Uniied Modeling Language) state diagrams into graphs by making explicit the intended semantics of the diagram. The process of state expansion in nested state diagrams is explained by graph transformations in three steps: (1) adding boundary nodes introducing a precise interface for the state to be expanded, (2) expanding the state, and (3) removing the boundary nodes. The general idea of approaching the semantics of UML diagrams by graph transformations is applicable to other forms of UML diagrams as well. The main advantage of the graph transformation approach is the closeness between the (mathematical) graph representation and the (UML) diagram representation.