Filter promotion transformation strategies for deriving efficient programs from Z specifications

In recent years there has been growing interest in systematic methods for refining Z specifications into programs. We consider a transformational programming strategy known as filter promotion and examine its use for refining a class of Z specifications into sequential as well as parallel programs. This strategy is particularly useful for transforming specification of generate and test problems into efficient algorithms. We find it convenient to use different notations at different level of abstractions: Z to capture the starting specification, Bird-Meertens functional notation to express algorithms and Hoare's CSP to describe parallelism and communications. The basic ideas are illustrated by systematic transformational developments of sequential and parallel algorithms for sorting and searching problems.