Possible worlds process algebras.

A non-deterministic process is viewed as a set of deterministic ones: its possible worlds. Each world represents a particular "solution" of non-determinism. Under this view of non-determinism as underspecification, nodeterministic processes are specifications, and the possible worlds represent the model space and thus the set of possible implementations. Then, refinement is inclusion of sets of possible worlds and can be used for stepwise specifications. This notion of refinement naturally induces new preorders (and equivalences) for processes that we characterize denotationally, operationally and axiomatically for a basic process algebra with nil, prefix and choice. [ABSTRACT FROM AUTHOR]