Transformations preserving properties and properties preserved by transformations in fair transition systems (extended abstract)

Abstract

Chandy and Misra's Unity, Back's Action Systems and Lamport's Temporal Logic of Actions (TLA) are three prime examples of specification formalisms for concurrent systems viewed as fair transition systems. The first two examples, and to a lesser extent the latter, also advocate a design methodology for formal derivation of concurrent systems or, rather, concurrent algorithms. Their program can be summarized as positing that algorithms should be designed without specific program control being forced upon the designer and that algorithms should be specified using properties that are (easily shown to be) preserved by the various transformations that one might use during the derivation process. For Misra and Chandy such transformations include union (i.e., parallel composition) and some forms of refinement but not hiding of variables. Back does consider hiding but ignores union as a property preserving transformation; as does, e.g., Lamport in his TLA.