HOOD and Z for the development of complex software systems

Abstract

Requirements for cost-effective high-quality software are becoming more and more stringent both in Safety-Critical and in Complex Software Development Environments. Stimulated in part by recent issues from the UK Ministry of Defence, the use of Formal Mathematical Methods is going to be taken into greater consideration also in industrial contexts due to their descriptive and analytical capabilities. Nevertheless, there is a little guidance as to the manner in which formal techniques should be effectively used. In the area of Software Engineering several methodologies can be found which effectively support the software development process in terms of costs and productivity, but, unfortunately, not in terms of quality and reliability. In this paper we propose to integrate the Z formal specification notation with the HOOD object-oriented design methodology (i.e. the standard European Space Agency design method). A twofold benefit is produced: on the one hand the structuring principles of HOOD compensate a class of problems which are peculiar to formal specifications in general and, on the other hand, the behaviour of a HOOD object can be formally described allowing us to rigorously verify some properties. Also, like a “Troian” horse, this could be a promising approach for promoting industrial use of formal methods.