A general framework for modular implementations of modular system specifications

Abstract

We investigate the impact of modularity on the semantics and on the implementation of software specifications. Based on the stratified loose semantics approach we develop a suitable specification framework which meets our basic requirements: the independent construction of implementations for the single constituent parts (modules) of a system specification and the encapsulated development of each implementation part using the principle of stepwise refinement.Our paper is not aimed at providing an elaborated specification language but rather to concentrate on the modularity issues of system development. Hence, only few but powerful constructs are provided which can be seen as a kernel for further extensions. In particular, we will show that implementation and parameterization can be handled within a uniform concept and we will prove compatibility theorems like the horizontal composition property. All constructs are defined on top of a very general logical framework thus being applicable to various kinds of specification formalisms.