Software maintenance via default theory evolution：Preliminary report

Abstract

This paper addresses the problem of automated support for software maintenance from the viewpoint of research in belief revision and default reasoning. We argue that formal specifications should be viewed as mutable specification theories, which we treat as default theories in a variant of default logic called PJ-default logic [3]. We show that this approach to analyzing formal specifications provides benefits not only in terms of a more powerful representation language, but also because it permits us to define a specification revision framework which supports reuse-oriented software maintenance. Our approach views specification revision as a process of mapping between default theories and provides us the ability to explicitly record retracted specifications and take them into account in deciding the outcomes of the specification revision process, the ability to retain specifications which would otherwise be discarded in a semantically well-founded manner in anticipation of future reuse. We argue that our approach is a longuage0independent method of analyzing and revising specifications in any formal specification language.