Non-functional requirements in the software development process

The satisfaction of a customer's non-functional requirements is an important factor in determining the acceptince of a designed system. They can be seen as constraints on either the final product or on the development process. Each such requirement may generate further constraints, depending on decisions taken, forming a graph, and a path can be traced between the original requirement and a design commitment. Work has been carried out on modelling where in the development process such decisions are best taken using Milner's Calculus of Communicating Systems, with agents representing roles and documents. A prototype support environment based on the model is being implemented using C and Motif.