Formal Methods in the IS Domain: Introducing a Notation for Presenting Object-Z Speci cations

The evaluation of an information systems development method (Swatman& Swatman, 1992) synthesised from research into: the object oriented approach mathematically formal speci cation languages socio-organisational contextual analysis. has led us to analyse the process by which models of the problem context (loosely, requirements speci cations) developed under this approach are validated. Our research suggests that user acceptors nd it useful to analyse the dynamics of interaction of objects within a system. In this paper, we describe a diagrammatic notation which we call `event chains' by which such analysis may be facilitated. Following our development approach (Swatman & Swatman, 1992), we focus on and demonstrate the application of the event chain notation in conjunction with the object oriented formal speci cation language Object-Z. We argue, however, that the event chain notation and its underlying philosophy are valuable independently of the mathematical formalism. We suggest a three-part approach to the presentation of speci cations: a managerial overview a behavioural perspective (event chains formalised by means of Object-Z schema fragments|exempli ed within this paper) a design perspective (Object-Z schemata embedded in explanatory text and supported by MOSES (Henderson-Sellers & Edwards, 1994) diagrams). and argue that, although there is redundancy in the presentation of the formal speci cation across parts two and three, such redundancy (and, hence, the potential for con ict within the speci cation) could be controlled mechanically.