A Meta-model for the Assessment of Non-Functional Requirement Size

Non-functional requirements (NFRs) pose unique challenges in estimating the effort it would take to implement them. This is mainly because of their unique nature; NFRs are subjective, relative, interactive and tending to have a broad impact on the system as a whole. Nevertheless, it is crucial, when making decisions about the scope of software by given resources and budget, to furnish a justifying and quantitative analysis based on both functional requirements (FRs) and NFRs. This paper presents a meta-model which complements the FR dimension with the NFRs as another dimension to be used in effort estimation approaches. The meta-model is deployed to extend the use of the COSMIC functional size measurement method to measure the size of NFRs, as effort is a function of size. We report on a case study to demonstrate our approach in context.