Tracing Non-Functional Requirements

Non-functional requirements, describing quality concerns such as performance, security, and availability, often exhibit complex interdependencies and trade-offs and have broad-reaching impacts across the architectural design of a software intensive system. This creates significant challenges for tracing NFRs, as traceability links can quickly proliferate and the traceability effort can be costly and impractical. As a result, many organizations do not even attempt to trace NFRs; however this means that functional changes are often implemented with very little understanding of how system qualities are affected by the change. The challenge, from a traceability perspective, is to develop effective techniques which simplify the task of creating and maintaining NFR-related traceability links, while still providing effective support for critical tasks such as impact analysis, requirements validation, and architectural preservation. In this chapter we first describe and evaluate existing methods for tracing NFRs and then propose a new pattern-based approach which leverages software architectural techniques to achieve NFR traceability. We illustrate our approach with examples from the mobile phone case study.