Supporting Release Planning of Quality Requirements: The Quality Performance Model

Abstract: In a competitive environment, as experienced by market-driven organizations, it is important to plan software product releases with time-to-market in mind. To increase the chances of market success, software products need to be released to the market, not only at the right time, but also with higher level of quality than the competitors' products. Thus quality requirements can be seen as a key competitive advantage. An especially challenging problem for an organization that develops software products offered to a market is to set the right quality target in relation to future market demands and competitor products. When is the quality level a competitive advantage? The goal of this thesis is to increase the awareness and understanding of quality requirements, and to find means for improving the ability to make early estimates of quality requirements, e.g., performance requirements, in order to enhance high-level decision-making related to release planning and roadmapping. This thesis is based on empirical research using a flexible research design. The research contains two qualitative surveys of quality requirements challenges in market-driven software product development organizations based on interviews with practitioners. From these surveys, issues emerge such as when the quality level is good enough, and how to get quality requirements into projects when functional requirements are prioritized. A case study within the embedded software domain investigates how quality requirements are classified and specified (including quantification) in an industrial context, which concludes that for a method to be successful, it is important that the method itself is flexible enough to handle the diverse nature of quality requirements. A model called QUPER (QUality PERformance) is evolved and evaluated in two organizations. The model aims at supporting release planning of quality requirements, and was found relevant by both organizations. Finally, a prototype tool for the QUPER model was developed and evaluated in a software organization. The QUPER prototype tool was found to provide a clear overview of the current market situation by the generated roadmaps, and to reach an alignment between practitioners, e.g., product managers and developers, of what level of quality is actually needed.