Model Checking of Message Sequence Charts

Rajeev Alur and Mihalis Yannakakis

Scenario-based specifications such as message sequence charts (MSC) offer an intuitive and visual way of describing design requirements. Such specifications focus on message exchanges among communicating entities in distributed software systems. Structured specifications such as MSC-graphs and Hierarchical MSC-graphs (HMSC) allow convenient expression of multiple scenarios, and can be viewed as an early model of the system. In this paper, we present a comprehensive study of the problem of verifying whether this model satisfies a temporal requirement given by an automaton, by developing algorithms for the different cases along with matching lower bounds.

When the model is given as an MSC, model checking can be done by constructing a suitable automaton for the linearizations of the partial order specified by the MSC, and the problem is coNP-complete. When the model is given by an MSC-graph, we consider two possible semantics depending on the synchronous or asynchronous interpretation of concatenating two MSCs. For synchronous model checking of MSC-graphs and HMSCs, we present algorithms whose time complexity is proportional to the product of the size of the description and the cost of processing MSCs at individual vertices. Under the asynchronous interpretation, we prove undecidability of the model checking problem. We, then, identify a natural requirement of boundedness, give algorithms to check boundedness, and establish asynchronous model checking to be PSPACE-complete for bounded MSC-graphs and EXPSPACE-complete for bounded HMSCs.

In Proceedings of the Tenth International Conference on Concurrency Theory (CONCUR'99), Lecture Notes in Computer Science 1664, Springer-Verlag, pp. 114--129, 1999.