Moving from interface theories to assembly theories

Abstract

We show how interface theories supporting pairwise component analysis can be extended in a generic way to a multi-component environment. This leads to the abstract framework of an assembly theory which captures notions of assembly refinement and communication-safety in assemblies of interacting components. An assembly theory supports also encapsulation of assemblies into interfaces and hence hierarchical constructions. We propose general rules that should be satisfied by any concrete assembly theory, like compositional construction and refinement of communication-safe assemblies. We discuss general procedures how to construct an assembly theory on top of a given interface theory such that (some of) the laws of an assembly theory are automatically guaranteed by the properties of an underlying interface theory. As a proof of concept we consider two instances of our approach. The first one starts from the (optimistic) interface theory of interface automata proposed by de Alfaro and Henzinger, and the second one from the (pessimistic) interface theory of modal I/O-interfaces. In the latter case, we propose a new notion of modal assembly refinement which has all the required properties, in particular it preserves modal communication-safety of assemblies. A small case-study illustrates how our concepts can be methodologically applied.