A Compiler for Multimodal Scenarios: Transforming LSCs into AspectJ

We exploit the main similarity between the aspect-oriented programming paradigm and the inter-object, scenario-based approach to specification, in order to construct a new way of executing systems based on the latter. Specifically, we transform multimodal scenario-based specifications, given in the visual language of live sequence charts (LSC), into what we call scenario aspects, implemented in AspectJ. Unlike synthesis approaches, which attempt to take the inter-object scenarios and construct intra-object state-based per-object specifications or a single controller automaton, we follow the ideas behind the LSC play-out algorithm to coordinate the simultaneous monitoring and direct execution of the specified scenarios. Thus, the structure of the specification is reflected in the structure of the generated code; the high-level inter-object requirements and their structure are not lost in the translation. The transformation/compilation scheme is fully implemented in a UML2-compliant tool we term the S2A compiler (for Scenarios to Aspects), which provides full code generation of reactive behavior from inter-object multimodal scenarios. S2A supports advanced scenario-based programming features, such as multiple instances and exact and symbolic parameters. We demonstrate our work with an application whose inter-object behaviors are specified using LSCs. We discuss advantages and challenges of the compilation scheme in the context of the more general vision of scenario-based programming.