Introduction

In software development, we have to make choices and take decisions, and these depend on obtaining answers for critical questions, such as the following:

• How should an important decision be made when conflicting strategic goals and stakeholders’ desires or quality attributes must be considered?

• How can stakeholders be assured that the decision has been made in a sound, rational and fair process that withstands the rigour of an aspect-oriented analysis and design, or a software product line, for example?

In software product line (SPL) development, the answers to these questions are critical, because they require dealing with modelling and implementation of common and variable requirements that can be composed and interact in different ways. Furthermore, they also require decisions that can impact several products at the same time. For example, we may simply want to know which requirements are in conflict and which features are negatively affected – considering different configurations of the software product lines – to choose the best architecture to design and implement the product line and to be able to decide which mandatory or optional features should have implementation priority. Therefore, help is required to support software engineers in making better, informed decisions, by offering them a systematic process for ranking a set of alternatives based on a set of criteria. In requirements engineering, for instance, it is useful to identify conflicting requirements with respect to which negotiations must be carried out and to which trade-offs need to be established (Rashid et al., 2003). A concrete typical use is to offer a ranking of non-functional requirements (NFRs) based on stakeholders’ wishes. This helps to establish early trade-offs between requirements, hence providing support for negotiation and subsequent decision-making among stakeholders. As discussed in Moreira et al. (2005a), having performed a trade-off analysis on the requirements, we are better informed with respect to each important quality attribute the system should satisfy, before making any architectural choices.