Composing Problems: Deriving specifications from inconsistent requirements

Laney, Robin; Jackson, Michael and Nuseibeh, Bashar (2005). Composing Problems: Deriving specifications from inconsistent requirements. Technical Report 2005/08; Department of Computing, The Open University.

DOI: https://doi.org/10.21954/ou.ro.00016030

Abstract

In this paper we demonstrate an approach to system development based on problem decomposition and subsequent (re)composition of sub-problem specifications. We illustrate the work using Problem Frames, an approach to the decomposition of problems that relates requirements, domain properties, and machine specifications. Having decomposed a problem, one approach to solving it is through a process of composing solutions to sub-problems. In this paper, we show that by formalizing system requirements and domain properties using an Event Calculus, we can both systematically derive machine specifications and solve composition problems. We add a prohibit predicate to the event calculus, that prohibits an event over a given time period. This allows a sub-solution to be formalized in a way that provides for run-time conflict resolution. We develop our earlier work on Composition Frames, an approach to composing inconsistent requirements, by adding systematic support and factoring out domain-dependent details. Throughout the paper we use a simple case study to illustrate and validate our ideas.