A Formal Approach to the Assessment of Priorities of Imprecise Conflicti ng Requirements

Two major changes with requirement engineering are (1) requirements are often imprecise in nature, and (2) requirements are usually conflicting with each other. One of the most important issues in the trade-off analysis of conflicting requirements is to understand the priority of requirements. Existing formal methods for requirement engineering are very limited in addressing these issues. This paper presents a formal methodology for specifying imprecise requirements, for characterizing complex relationships among them, for assessing their priority, and for facilitating the trade-off analysis. Imprecise requirements are represented by the canonical form in test-score semantics in fuzzy logic. Two kinds of relationships between requirements (i.e., conflicting and cooperative) are formally introduced. Multiple requirements with different priorities are aggregated based on the fuzzy multi-criteria decision technique. The assessment of the priority of requirements is facilitated by analyzing the trade-offs between partial satisfaction of these imprecise requirements. The proposed approach can contribute not only to an early identification of conflicting requirements, but also to a better understanding of the nature of conflict, which is vital to the negotiation process and the trade-off analysis during the design phase.