Textual User Requirements Notation

The User Requirements Notation (URN) is a requirements engineering standard published by the International Telecommunication Union that combines goal and scenario modeling in support of the elicitation, specification, analysis, and validation of requirements. The URN standard focuses on a graphical notation. This paper introduces a textual notation for URN called TURN (Textual User Requirements Notation). The main objective of TURN is to support the modeling of very large URN specifications where thousands of separate goal graphs or scenarios become unwieldy to navigate. In addition, the entering of large specifications in graphical tools has proven tedious, as the modeler must be concerned with layout issues that are unrelated to the information that is attempted to be modeled. In general, TURN offers an alternative input medium for URN specifications which aims to be easier, faster, and more scalable. Xtext is the defacto standard for the specification of textual metamodel-based software languages. To validate the feasibility of TURN, it is specified as an Xtext grammar, resulting in a metamodel tailored to TURN and covering a large subset of URN. The differences between the URN standard and TURN are elaborated, a multi-phased model-to-model transformation from TURN to URN is described, and conformance to URN is demonstrated with a rather exhaustive set of test cases for TURN specifications and their transformations.