Scalable Redundancy Detection for Real-Time Requirements

Describing a system in a requirements specification demands correctness and conciseness. Requirements are redundant if they are stated multiple times throughout a specification (explicitly or implicitly). In contrast to vacuity, redundancies do not inherently indicate specification defects, and are sometimes even inevitable to adequately follow safety practices. However, intended redundancies have to be managed to avoid subsequent errors. Unintended redundancies often hint to defects in the requirements specification. We present an analysis for redundancies in formal real-time requirements specifications based on automata theoretical model checking. To enable this analysis, we introduce a determinism preserving totalization and complement procedure for the timed automaton model of Phase Event Automata. We state the redundancy check for a set of real-time requirements as a program analysis task. Benchmarks show the viability of our approach to analyse requirements sets of industrial size and complexity: the analysis scales well on industrial sets, interesting redundancies both from requirements and as a formalisation artefact were found.