Towards a practically extensible Event-B methodology

Abstract

Formal modelling is increasingly recognised as an important step in the development of reliable computer software. Mathematics provide a solid theoretical foundation upon which it is possible to specify and implement complex software systems. Event-B is a formalism that uses typed set theory to model and reason about complex systems. Event-B and its associated toolset, Rodin, provide a methodology that can be incorporated into the development process of software and hardware. Refinement and mathematical proof are key features of Event-B that can be exploited to rigorously specify and reason about a variety of systems. Successful and usable formal methodologies must possess certain attributes in order to appeal to end-users. Expressiveness and extensibility, among other qualities, are of major importance. In this thesis, we present techniques that enhance the extensibility of: (1) the mathematical language of Event-B in order to enhance expressiveness of the formalism, and (2) the proving infrastructure of the Rodin platform in order to cope with an extensible mathematical language. This thesis makes important contributions towards a more extensible Event-B methodology.Firstly, we show how the mathematical language of Event-B can be made extensible in a way that does not hinder the consistency of the underlying formalism. Secondly, we describe an approach whereby the prover used for reasoning can be augmented with proof rules without compromising the soundness of the framework. The theory component is the placeholder for mathematical and proof extensions. The theoretical contribution of this thesis is the study of rewriting in the presence of partiality. Finally, from a practical viewpoint, proof obligations are used to ensure soundness of user-contributed extensions