Refinement and reachability in event_b

  • Authors:
  • Jean-Raymond Abrial;Dominique Cansell;Dominique Méry

  • Affiliations:
  • ETHZ Zurich, Switzerland;LORIA, Université de Metz, France;LORIA, Université Henri Poincaré Nancy 1, France

  • Venue:
  • ZB'05 Proceedings of the 4th international conference on Formal Specification and Development in Z and B
  • Year:
  • 2005

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Abstract

Since the early 90's (after the seminal article of R. Back [4]), the refinement of stuttering steps [5] are performed by means of new actions (called here events) refining skip. It is shown in this article that such a refinement method is not always possible in the development of large systems. We shall instead use events refining some kind of non-deterministic actions maintaining the invariant (sometimes called keep). We show that such new refinements are completely safe. In a second part, we explain how such a mechanism can be used to express some reachability conditions that were otherwise expressed using some special temporal logic statements à la TLA [5] in a previous article [2]. Examples will be used to illustrate our proposals.