Heuristics for refinement relations

A refinement relation, by documenting the relationship between the states of abstract and concrete systems, forms the basis for deriving the operations of the latter from those of the former However that approach requires the choice of an appropriate refinement relation and contains no 'redundancy', or room for error, since the (weakest) concrete system is entirely specified by the abstract system and the refinement relation. We provide heuristics to guide the choice of refinement relation, based on augmenting a state-based specification with laws of the kind used in algebraic specification or that arise from the general properties of reachability and full abstraction. The combination of static and dynamic information confers some redundancy that is useful to confirm the choice of refinement relation or, as presented here, aid its definition. We conclude that for practical purposes there is much to recommend the combination of state-based and algebraic specification techniques.