Monotone predicate transformers as up-closed multirelations

  • Authors:
  • Ingrid Rewitzky;Chris Brink

  • Affiliations:
  • Department of Mathematical Sciences, University of Stellenbosch, South Africa;Department of Mathematical Sciences, University of Stellenbosch, South Africa

  • Venue:
  • RelMiCS'06/AKA'06 Proceedings of the 9th international conference on Relational Methods in Computer Science, and 4th international conference on Applications of Kleene Algebra
  • Year:
  • 2006

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Abstract

In the study of semantic models for computations two independent views predominate: relational models and predicate transformer semantics. Recently the traditional relational view of computations as binary relations between states has been generalised to multirelations between states and properties allowing the simultaneous treatment of angelic and demonic nondeterminism. In this paper the two-level nature of multirelations is exploited to provide a factorisation of up-closed multirelations which clarifies exactly how multirelations model nondeterminism. Moreover, monotone predicate transformers are, in the precise sense of duality, up-closed multirelations. As such they are shown to provide a notion of effectivity of a specification for achieving a given postcondition.