USER REQUIREMENTS NOTATION

Several years ago, the standardization sector of the International Telecommunications Union initiated work toward the creation of a user requirements notation (URN) in the Z.150 series of Recommendations (ITU-T, 2003). The purpose of URN is to support, prior to detailed design, the modeling and analysis of user requirements in the form of goals and scenarios, in a formal way. URN is generally suitable for describing most types of reactive and distributed systems and services. It is also a convenient notation for business process modeling and evolution (Weiss & Amyot, 2005). An overview of URN with a tutorial example from the wireless communication domain is presented in Amyot (2003). The appendix at the end of this chapter also includes a summary of the main notation elements.

URN has concepts for the specification of behavior, structure, and goals, which are all relevant for the formalization of pattern forces and solutions, and for trade-off analysis. URN is, in fact, composed of two complementary notations, which build on previous work. The first is GRL, the goal-oriented requirement language (URN Focus Group, 2003a). GRL borrows its main concepts from the NFR (Non-functional requirements) framework published in Chung et al. (2000), and complements them with agent modeling concepts from the i* framework (Yu, 1997). GRL captures business or system goals, alternative means of achieving goals, and the rationale for goals and alternatives. The notation is applicable to functional requirements, but it is especially good for capturing and reasoning about the interaction of non-functional requirements.