Feature Refinement

Development by formal stepwise refinement offers a guarantee that an implementation satisfies a specification. But refinement is frequently defined in such a restrictive way as to disallow some useful development steps. Here we define feature refinement to overcome some limitations of refinement and show its usefulness by applying it to examples taken from the literature. Using partial relations as a canonical state-based semantics and labelled transition systems as a canonical event-based semantics, we define functions formally linking the state- and event-based operational semantics. We can then use this link to move notions of refinement between the event- and state-based worlds. An advantage of this abstract approach is that it is not restricted to a specific syntax or even a specific interpretation of the operational semantics.