Refinement of fair action systems

Abstract.

An action system is a framework for describing parallel or distributed systems, for which the refinement calculus offers a formalisation of the stepwise development method. Fairness is an important notion in modelling parallel or distributed systems, and this paper investigates a calculus for refinement of fair action systems. Simulations, which are proof techniques for refinement, are extended to verify fair action systems. Our work differs from others' in that the additional condition concerning fairness is expressed through termination of related iteration statements. For this purpose, existing proof rules for termination are extended. In the tradition of the refinement calculus, our approach to fairness is based on techniques developed mainly for sequential programming.