Consistency between UML Classes and Associated State Machines

One of the main advantages of the UML is its possibility to model different views on a system using a number of diagram types. The various diagrams can be used to specify different aspects and their combination together makes up the complete system description. This does, however, always pose the question of consistency: it may well be the case that the designer has specified contradictory requirements which can never be fulfilled together. In this paper, we study consistency problems arising between static and dynamic diagrams, in particular between a class and its associated state machine. We propose a definition of consistency which is based on a common formal semantics for both classes and state machines, and discuss the merits and disadvantages of this definition on a simple case study. On this case study we furthermore show how consistency checks can be supported by a model checker. Finally we present consistency preserving transformations on the static as well as the dynamic part.