Distributing refinements of a system-level partial behavior model

Abstract

Early in a system's life cycle, a system's behavior is typically partially specified using scenarios, invariants, and temporal properties. These specifications prohibit or require certain behaviors, while leaving other behaviors uncategorized into either of those. Engineers refine the specification by eliciting more requirements to finally arrive at a complete behavioral description. Partial-behavior models have been utilized as a formal foundation for capturing partial system specifications. Mapping the requirements to partial behavior models enables automated analyses (e.g., requirements consistency checking) and helps to elicit new requirements. Under the current practices, software systems are reasoned about and their behavior specified exclusively at the system level, disregarding of the fact that a system typically consists of interacting components. However, exclusively refining a behavior specification at the system-level runs the risk of arriving at an inconsistent specification, i.e. one that is not realizable as a composition of the system's components. To address this problem, we propose a framework that provides the lacking support: a newly specified requirement implicitly refines the system's underlying partial behavior model; our framework maps the new requirement to components by automatically distributing the system model refinements to the components' underlying models. By doing so, our framework prevents requirements inconsistencies and helps to identify further necessary requirements. We discuss the framework's soundness and correctness, and demonstrate its features on a case study previously used in related literature.