Action Refinement as an Implementation Relation

We propose a theory of process refinement which relates behavioural descriptions belonging to conceptually different abstraction levels, through a so-called vertical implementation relation. The theory is based on action refinement, which permits to relate abstract actions of the implementation to concrete computations of the implementation; it is developed in the standard interleaving approach. A number of proof rules is shown to be sound for the particular vertical implementation relation (based on observation congruence) we study in this paper. We give an illustrative example