Dealing with non-functional requirements

Quality characteristics are vital for the success of software systems. To remedy the problems inherent in ad hoc development, a framework has been developed to deal with non-functional requirements (quality requirements or NFRs). Taking the premise that the quality of a product depends on the quality of the process that leads from high-Ievel NFRs to the product, the framework's objectives are to represent NFR-specific requirements, consider design tradeoffs, relate design decisions to IYFRs, justify the decisions, and assist defect detection. The purpose of this paper is to give an initial evaluation of the extent to which the framework's objectives are met. Three small portions of information systems were studied by the authors using the framework. The framework and empirical studies are evaluated herein, both from the viewpoint of domain experts who have reviewed the framework and studies, and ourselves as framework developers and users. The systems studied have a variety of characteristics, reflecting a variety of real application domains, and the studies deal with three important classes of NFRs for systems, namely, accuracy, security, and performance. The studies provide preliminary support for the usefulness of certain aspects of the framework, while raising some open issues.