Another characterization of weakest preconditions

We present an approach to the study of nondeterministic programs, consisting essentially in using binary relations as semantic objects representing the input-output behaviour of programs. These relations include an explicit representation of non-terminating computations. Based on the relational model we introduce a weakest precondition total correctness predicate transformer. We then show how to build up this predicate transformer starting from others of a more e1ementar kind. Fina11y,we obtain a,characterization of its healthiness properties in terms of set-theoretical propert~ ies of the relations involved.