Modeling Nonfunctional Requirements – A Case Study

A key to successful software development is a clear understanding of the requirements. Requirement analysis is to be carried out at the earlier stage of software development life cycle to avoid requirement related problem at a later stage. Both functional (FR) and non-functional requirement (NFR) play crucial role in software development. A common industrial practice is not to consider NFR at the earlier stage of software development, hence NFR may not be reflected in the design stage and it may lead to a failed product. Addressing these issues, this work-in progress paper extends the traditional feature diagram to model NFR of a system along with its functional features. Such model facilitates a clear view of both NFR and FR at the early stage of system development. An extension of UML use case diagram is demonstrated that enables the elicitation and modeling of NFR in a convenient manner. A case study of Point of Sale (POS) system is presented illustrating the NFR modeling steps. Keywords— NFR, feature diagram, point of sale, UML