A pattern-based method for refining and formalizing informal specifications in critical control systems

Processing specifications is an issue of crucial importance when developing critical complex systems. In particular, establishing rigorous specifications broadly impacts the subsequent engineering phases. This paper discusses a refinement technique for processing informal specifications expressed in a literal shape, with the aim to generate formal specifications appropriate to automatic processing. The developed technique carries out an iterative process which relies on a set of basic refinement patterns that we have established, and ends up with a formalization step which actually generates logical CTL* formulas. Furthermore, the method implements traceability facilities, which allow for a tidy backtracking of the whole process. The concepts introduced to set up the various mechanisms are discussed and a case study featuring an embedded railway control system is used to illustrate our technique.