How Architects See Non-Functional Requirements: Beware of Modifiability

This paper presents the analysis and key findings of a survey about dealing with non-functional requirements (NFRs) among architects. We find that, as long as the architect is aware of the importance of NFRs, they do not adversely affect project success, with one exception: highly business critical modifiability tends to be detrimental to project success, even when the architect is aware of it. IT projects where modifiability is perceived to have low business criticality lead to consistently high customer satisfaction. Our conclusion is that modifiability deserves more attention than it is getting now, especially because in general it is quantified and verified considerably less than other NFRs. Furthermore, IT projects that applied NFR verification techniques relatively early in development were more successful on average than IT projects that did not apply verification techniques (or applied it relatively late in development).