Application of Stuck-Free Conformance to Service-Role Composition

We use SDL and UML 2.0 state machines for behavior modeling of communication control software for telecommunication services. To ensure consistent designs we want to identify when a signal sent is not consumed and when a state machine waits indefinitely for a signal that never arrives. One approach to ensure such consistency is to derive interface contracts for each port from the properties of the state machine and use the contracts to check consistency. In this paper we describe how Calculus for Communicating Systems (CCS) [1] and stuck-free conformance [2] can be used as a formal fundament for this consistency checking. Interface descriptions should be comprehensible without having to learn process algebra. Therefore we introduce a graphical notation for both the port contracts and for the interaction made possible across the interface of two state machines.