Generating Programs Plus Proofs by Refinement

Refinement-oriented development starts with the requirements of the procuring organization. These requirements are typically a mixture of informal and semiformal notations that reflect the needs of the organization. To provide the basis for a clear contract, the requirements must be formalized into specifications that both the procuring organization (the buyer) and the developer (the seller) can agree to. Specifications can be expressed at a variety of levels of abstraction. At one extreme a suitable high-level programming language can sometimes serve to express executable specifications. However, an executable specification requires the inclusion of implementation detail that (1) is time-consuming to develop and get right, and (2) might be better left to the developer’s discretion. At the other extreme, a property-oriented language (such as a higher-order logic) can be used to prescribe the properties of the intended software with minimal prescription of implementation detail. The solution in Specware is a mixture of logic and high-level programming constructs that provides a wide-spectrum approach, allowing specification writers to choose an appropriate level of abstraction from implementation detail.