Control case approach to record and model non-functional requirements

While the functional requirements of a system can be effectively modeled through the use case driven approach, there is no standard or de facto method for modeling non-functional requirements (NFR) of the system architecture. Often such requirements are dealt with in a reactive manner, rather than proactively. Yet increasingly a contributing factor in project difficulty and failure are the NFR imposed on the solution architecture. This paper outlines a control case approach to record and model NFR. This technique enables the control case to represent the NFR from different perspectives, most typically the various operating conditions. We also propose an extension to the "4 + 1" view model for depicting software architecture by adding the control case view. In addition, a detailed control case modeling example is illustrated to demonstrate how these techniques may be applied during development. Taken together, we suggest that the combination of both the use case and control case views thus reflects the complete requirements across the collective system life cycle views: design, process, implementation and deployment. © Springer-Verlag 2007.