What you ask is what you get: Understanding architecturally significant functional requirements

Software architects are responsible for designing an architectural solution that satisfies the functional and non-functional requirements of the system to the fullest extent possible. However, the details they need to make informed architectural decisions are often missing from the requirements specification. An earlier study we conducted indicated that architects intuitively recognize architecturally significant requirements in a project, and often seek out relevant stakeholders in order to ask Probing Questions (PQs) that help them acquire the information they need. This paper presents results from a qualitative interview study aimed at identifying architecturally significant functional requirements' categories from various business domains, exploring relevant PQs for each category, and then grouping PQs by type. Using interview data from 14 software architects in three countries, we identified 15 categories of architecturally significant functional requirements and 6 types of PQs. We found that the domain knowledge of the architect and her experience influence the choice of PQs significantly. A preliminary quantitative evaluation of the results against real-life software requirements specification documents indicated that software specifications in our sample largely do not contain the crucial architectural differentiators that may impact architectural choices and that PQs are a necessary mechanism to unearth them. Further, our findings provide the initial list of PQs which could be used to prompt business analysts to elicit architecturally significant functional requirements that the architects need.