Compositional Reenement of Interactive Systems

We describe systems and their components by functional speciication techniques. We deene notions of interface and interaction reenement for interactive systems and their components. These notions of reenement allow one to change both the syntactic (the number of channels and sorts of messages at the channels) and the semantic interface (causality ow between messages and interaction granularity) of an interactive system component. We prove that these notions of reenement are compositional with respect to sequential and parallel composition of system components, communication feedback and recursive declarations of system components. According to these proofs reenements of networks can be accomplished in a modular way by reening their components. We generalize the notions of reenement to reening contexts. Finally full abstraction for speciications is deened and compositionality with respect to this abstraction is shown, too.