Behavioural Conflicts in a Causal Specification

Abstract

Inconsistencies may arise in the course of specification of systems, and it is now recognised that they cannot be forbidden. Recent work has concentrated on enabling requirements descriptions to tolerate inconsistency and on proposing notations that permit inconsistency in specifications. We approach the subject by examining the use of an existing causal language, which is used as a means of specifying the behaviour of systems, to specify, identify and resolve behavioural inconsistencies. This paper is an exploration of the kinds of inconsistency that can arise in a causal specification, how they can be discovered and how they can be resolved. We distinguish between inconsistencies in the structure of a specification, which are assumed to have been removed previously, and inconsistencies in behaviour which, being dynamic in nature, we describe as conflicts. Our approach concentrates on the identification of conflicts in the specified behaviour of a system. After summarising the causal language, we describe a classification of behavioural conflicts and how they can be identified. We discuss possible methods of resolution, and propose a simple process to aid the identification and resolution of conflicts. A case study using the causal language illustrates our approach.