A Logical Framework for Modeling and Reasoning About the Evolution of Requirements

We present a logical framework for modeling and reasoning about the evolution of requirements. We demonstrate how a sufficiently rich meta level logic can formally capture intuitive aspects of managing changes to requirements models, while maintaining completeness and consistency. We consider a theory as the deductive closure of a given set of axioms and conclude that software engineering is concerned, in essence, with, building and managing large theories. This theory construction commences with the development of the requirements model which we view as a theory of some nonmonotonic logic. Requirements evolution then involves the mapping of one such theory to another. Exploiting the deductive power of the theory of belief revision and nonmonotonic reasoning we develop a formal description of this mapping, as well as the requirements engineering process itself. This work thus offers a rigorous approach to reasoning about requirements evolution and a important focus for defining semantically well founded methods and tools for the effective management of changing requirements.