Non-Functional Requirements Size Measurement Method (NFSM) with COSMIC-FFP

Non-functional requirements (NFRs) of software systems are an important source of uncertainty in effort estimation. Furthermore, quantitatively approaching NFR early in a project is difficult. This paper makes a step towards reducing the impact of uncertainty due to NFRs. It offers a new generic classification of the NFRs, and a NFR size measurement method (NFSM) that incorporates NFRs into the functional size quantification process. We chose the NFR framework as a vehicle to integrate NFRs into the requirements modeling process and to apply quantitative assessment procedures. Our solution proposal also rests on the functional size measurement method, COSMIC-FFP, adopted in 2003 as the ISO/IEC 19761 standard. We discuss the advantages of our approach and the open questions related to its design as well.