From Formal Specification in Event-B to Probabilistic Reliability Assessment

Abstract

Formal methods, in particular the B Method and its extension Event-B, have proven their worth in the development of many complex software-intensive systems. However, while providing us with a powerful development platform, these frameworks poorly support quantitative assessment of dependability attributes. Yet, such an assessment would facilitate not only system certification but also system development by guiding it towards the design optimal from the dependability point of view. In this paper we demonstrate how to integrate reliability assessment performed by model checking into refinement process in Event-B. Such an integration allows us to combine logical reasoning about functional correctness with probabilistic reasoning about reliability. Hence we obtain a method that enables building the systems that are not only correct-by-construction but also have a predicted level of reliability.