Steve Easterbrook, Robyn Lutz, Rick Covington, John Kelly, Yoko Ampo, David Hamilton
This paper describes three case studies in the lightweight application of formal methods to requirements modeling for spacecraft fault protection systems. The case studies differ from previously reported applications of formal methods in that formal methods were applied very early in the requirements engineering process, to validate the evolving requirements. The results were fed back into the projects, to improve the informal specifications. For each case study we describe what methods were applied, how they were applied, how much effort was involved and what the findings were. In all three cases the formal modeling provided a cost-effective enhancement of the existing verification and validation processes. We conclude that the benefits gained from early modeling of unstable requirements more than outweigh the effort needed to maintain multiple representations.
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