Requirements as Goals and Commitments Too

In traditional software engineering research and practice, requirements are classified either as functional or non-functional. Functional requirements consist of all functions the system-to-be ought to support, and have been modeled in terms of box-and-arrow diagrams in the spirit of SADT. Non-functional requirements include desired software qualities for the system-to-be and have been described either in natural language or in terms of metrics. This orthodoxy was challenged in the mid-90s by a host of proposals that had a common theme: all requirements are initially stakeholder goals and ought to be elicited, modeled and analyzed as such. Through systematic processes, these goals can be refined into specifications of functions the system-to-be needs to deliver, while actions assigned to external actors need to be executed. This view is dominating Requirements Engineering (RE) research and is beginning to have an impact on RE practice. We propose a next step along this line of research, by adopting the concept of conditional commitment as companion concept to that of goal. Goals are intentional entities that capture the needs and wants of stakeholders. Commitments, on the other hand, are social concepts that define the willingness and capability of an actor A to fulfill a predicate φ for the benefit of actor B, provided B (in return) fulfills predicate ψ for the benefit of actor A. In our conceptualization, goals are mapped to collections of commitments rather than functions, qualities, or actor assignments. We motivate the importance of the concept of commitment for RE through examples and discussion. We also contrast our proposal with state-of-theart requirements modeling and analysis frameworks, such as KAOS, MAP, i* and Tropos.