Dijkstra and Beverly A . Sanders , 1996 A predicate transformer for the progressproperty ` to - always

The temporal property`to-always' has been proposed for specifying progress properties of concurrent programs. Although thèto-always' properties are a subset of thèleads-to' properties for a given program, `to-always' has more convenient proof rules and in some cases more accurately describes the desired system behavior. In this paper, we give a predicate transformer wta, derive some of its properties, and use it to deenèto-always'. Proof rules for`to-always' are derived from the properties of wta. We conclude by brieey describing two application areas, nondeterministic data ow networks and self-stabilizing systems wherèto-always' properties are useful.