Integrating quality requirements in agile software development at scale: Challenges, approach and validation

This dissertation focuses on the engineering of Quality Requirements (QRs)—also known as non-functional requirements—within agile software development, particularly in Agile Large-Scale Distributed (ALSD) environments. While agile methods adopt a Just-In-Time approach where functional requirements evolve incrementally, this model is not well-suited to QRs. Unlike functional requirements, QRs represent long-term objectives like performance, security, and scalability, which must be addressed early in the Software Development Life Cycle to ensure they are embedded in the system architecture.

Agile methods were originally designed for small, co-located teams to counter the inflexible and document-heavy nature of traditional waterfall models. As agile gained popularity, large and distributed organizations began adopting these methods. However, this transition introduced new challenges, especially in handling QRs. Empirical studies show that QRs are often neglected in agile projects, a problem exacerbated in large-scale distributed settings due to increased complexity and communication barriers.

In response, this research investigates the specific challenges that agile teams face in managing QRs in ALSD environments. Fifteen key challenges were identified, along with their root causes and the mitigation strategies currently employed by agile teams. The study also evaluated existing Agile Scaled Frameworks (ASFs) to determine their effectiveness in addressing QR-related challenges. While ASFs offer partial solutions, significant gaps remain, particularly in cross-team communication and consistent QR handling.

To address these shortcomings, the dissertation introduces the Agile Quality Requirements Elaboration (AQRE) approach. AQRE is a Goal-Oriented Requirements Engineering method designed to facilitate early identification and continuous management of QRs throughout agile projects. The approach supports structured discussion of QRs from the outset and ensures their integration throughout development.

AQRE was validated through its application in a real-world agile project and assessed via Focus Group sessions with agile practitioners. Feedback indicated that AQRE is both practical and potentially cost-effective, offering a structured means to enhance QR handling in complex agile environments.