Syntactic detection of process divergence and non-local choice in message sequence charts

Abstract

Message Sequence Charts (MSCs) are increasingly used in software engineering methodologies and tools to capture, for instance, system requirements, test scenarios, and simulation traces. They have been standardized by ITU-T in Recommendation Z.120 [IT96]. However, various aspects Of environment behavior remain underspecified in MSCs, e.g., the presence of resources for inter-process communication and the coordination of concurrent processes at points of control branching. Such under specifications can result in ambiguities in an MSC specification and discrepancies between an MSC specification and its implementation. In this paper we characterize two consequences of harmful under specifications: process divergence and non-local branching choice. We also present two syntax-based analysis algorithms that detect both problems.