An Integrated Framework for Scenarios and State Machines

This paper develops a semantic framework for interpreting heterogeneous system specifications consisting of a mixture of scenario-based requirements and state-based design. Such specifications arise naturally in spiral- and refinement-based development methodologies in which parts of a system have detailed designs while others exist in more abstract form as a collection of requirements. More precisely, we consider the scenario-based notation of Triggered Message Sequence Charts (TMSCs) and the state-based notation of Communicating State Machines (CSMs), and show how they may be integrated in a semantic framework that is founded on the mathematical theory of acceptance trees. Our semantic theory is also equipped with a robust notion of refinement, which allows us to relate one heterogeneous specification with another. A case-study serves to illustrate the utility of our framework as a basis for the principled evolution of higher-level requirements to lower-level operational specifications.