Detecting Implied Scenarios in MSCs Using LTSA

Scenario-based specifications such as Message Sequence Charts (MSCs) are becoming increasingly popular as part of a requirements specification. Scenarios describe how system components, the environment and users working concurrently interact in order to provide system level functionality. Each scenario is a partial story which, when combined with other scenarios, should conform to provide a complete system description. However, it is not always possible to build a set of components that provides exactly the same system behaviour as described with a set of scenarios. Implied scenarios may appear as a result of unexpected component interaction. In this paper, we present an algorithm that builds a behaviour model that describes the closest possible implementation for a specification based on basic and high-level MSCs. We also present a technique for detecting and providing feedback on the existence of implied scenarios. We have integrated these procedures into the Labelled Transition System Analyser, which allows for model checking and animation of the behaviour model.