The Requirements/Service/Interface (RSI) Approach to Use Case Analysis

• Authors: Mark Collins-Cope
• Venue: TOOLS '99 Proceedings of the Technology of Object-Oriented Languages and Systems
• Year: 1999

Use case analysis is a requirements capture technique that is most often used in the early stages of OO and component development projects. It was first introduced by Ivar Jacobson in his book "Object Oriented Software Engineering" [1], although the description of use case analysis presented in this book has, in practise, been interpreted in many different ways (one of the consequences of which is that, seemingly at least, no two use case analysis projects ever deliver the same information).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 descibes at the RSI approach to use case analysis. This appraoch provides a framework for analysing and understanding potential use case deliverables and their inter-relationships, with a view to answering the questions detailed above. The RSI approach also aims to assist in maximising software re-use - by partitioning functionality into those aspects which are concerned with 'managing the interface' to an actor, and those areas which make up the re-usable core of the system.