The application of use cases in systems analysis and design specification

This paper begins by reviewing the application of use cases in the analysis and design phases of software development. At present, a use case derived in analysis is generally mapped into design through the synthesis of object behaviour for all scenarios associated with the use case. Hence the use case level of abstraction is not directly used in this process and a semantic gap exists between analysis and design. With informal textually based use case definitions this is to be expected, however, if the use cases themselves are given a more concrete structure, for example in the form of a statechart, then their direct use becomes more feasible.In this paper we therefore investigate the application of use case structures in the initial design phases of software development. A novel approach is proposed that applies a state based use case model directly to each object in the design architecture. This requires the derivation of a set of repeatable refinement procedures, which remove redundancy and allow the assignment of behaviour to objects with respect to their responsibilities. It is then shown how such procedures may be used in design, filling the semantic gap between analysis and design. By applying the procedures to a case study we identify and evaluate the characteristics of the mapping from use case model to object behaviour and review our approach with respect to other methods. It is concluded that state based use case structures not only represent a succinct analysis format, but may also be used to map analysis models directly into the design process.