Extending the NFR framework with measurable non-functional requirements

Accurate and correctly specified requirements are extremely important in ensuring the production of feasible software products. To assure that the requirements have actually been implemented, there has to be a trace link from requirements to implementation. Thus far requirement engineering has been a rather separate task from software design and implementation from the process point of view. This separation has a negative impact on requirements traceability and further, to product quality. Tracing of nonfunctional requirements (NFRs), such as performance, has been particularly cumbersome. Thus, in this paper we apply and extend the NFR Framework to bridge the gap between NFRs and implementation. We have implemented the extended NFR Framework, which we call NFR+ Framework, as a modelling language including a softgoal interdependency graph validation tool with a MetaCase MetaEdit+ language workbench. We extended the NFR Framework with a concept of measurable NFRs that enables to empirically verify the realization of defined NFRs in a product. The usage of the extended NFR Framework is demonstrated with a laboratory case.