FORMAL REQUIREMENTS AND DESIGN SPECIFICATIONS: THE CLEPSYDRA METHODOLOGY

摘要

The use of formal methods early in the development process has been advocated as a way of improving the quality of software products and their production process. Here we study the influence of a formal requirements document on the next phase in the software process, that is design. We suggest that formal design should coherently follow from formal requirements. We show that two different formal notations can be effectively used, one for writing requirements specification and one for design specification. We also consider how a design specification can be formally checked with respect to requirements specification. The notations we choose are well known: the Z notation for requirements and the Larch two-tiered language for design. We show how a number of tools based on these notations can be used to improve the quality of the documents produced during the development process.