Angelic Nondeterminism and Unifying Theories of Programming

Hoare and He's unifying theories of programming (UTP) is a model of alphabetised relations expressed as predicates, which supports development in several programming paradigms. The aim is the unification of languages and techniques, so that we can benefit from results in different contexts. In this paper, we investigate the integration of angelic nondeterminism in the UTP; we propose the unification of a model of binary multirelations, which is isomorphic to the monotonic predicate transformers model and can express angelic and demonic nondeterminism.