Syntactic Analysis of Message Sequence Chart Specifications

Abstract

Message Sequence Charts (MSCs) are gaining popularity in software engineering methods for concurrent and real-time systems. They are increasingly supported in software engineering 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 aspects of environment behavior remain underspecified in MSCs, e.g., the presence of resources for inter-process communication and the coordination of oncurrent processes at points of control branching. Such underspecifications 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 underspecifications: process divergence and non-local branching choice. We also present two syntax-based analysis algorithms that detect both problems. The syntactic characterization of these problems requires an MSC specification to be deadlock-free. Therefore, we also discuss deadlock detection in MSC specifications.