The requirements/service/interface (RSI) approach to use case analysis (a pattern for structured use case development)

Use case analysis is a requirements capture technique that is most often used in the early stages of OO and component development projects. When engineers first undertake use case analysis, a number of issues are raised for which easy answers can't be found in the text books, such as: what is the appropriate level of granularity for use cases? If large grained use cases are used, should they decomposed into 'lower level' use cases? If so, at what point should this decomposition stop, and how should these sub-use cases be used? Should user or external system interface functionality be described in use case text? How do dialog descriptions fit in? Where do report layouts go? Should user interface dynamics be included? Should interchange file formats, or interface protocols form part of the documentation? This paper describes the RSI approach to use case analysis. This approach provides a framework for analysing and understanding potential use case deliverables and their interrelationships, with a view to answering the above questions. The RSI approach also aims to assist in maximising software reuse-by partitioning functionality into those aspects which are concerned with 'managing the interface' to an actor and those areas which make up the reusable core of the system.