Note CS-N8901. Amsterdam, The Netherlands: Centre for Mathematics and Computer Science, 1989.
Abstract: In this paper it is shown that there are several equivalences based on partial orders which are not preserved by refinement (namely when taking the choice structure of systems into account); that nevertheless a ``branching time'' partial order equivalence can be found that is preserved under refinement; but that, in order to achieve preservation under refinement it is not necessary to employ partial order semnatics: there exist equivalences that abstract from the causal structure of concurrent systems and are still preserved under refinement.
Keywords: partial order semantics; refinement (of actions); branching time partial order equivalence; causal structure.