Syntactic Analysis of Message Sequence Chart Speciications

Message Sequence Charts (MSCs) are gaining popularity in software engineering methodsfor concurrent and real-time systems. They are increasingly supported in software engineer-ing tools to capture, for instance, system requirements, test scenarios, and simulation traces.MSCs have been standardized by ITU-T in Recommendation Z.120 [15]. However, various as-pects of environment behavior remain underspeci ed in MSCs, e.g., the presence of resources forinter-process communication and the coordination of concurrent processes at points of controlbranching. Such underspeci cations can result in ambiguities in an MSC speci cation and dis-crepancies between an MSC speci cation and its implementation. In this paper we characterizetwo consequences of harmful underspeci cations: process divergence and non-local branchingchoice. We also present two syntax-based analysis algorithms that detect both problems. Thesyntactic characterization of these problems requires an MSC speci cation to be deadlock-free.Therefore, we also discuss deadlock detection in MSC speci cations.2