Recommendation ITU-T Z.151 defines the User Requirements Notation (URN) intended for the elicitation, analysis, specification, and validation of requirements. URN combines modelling concepts and notations for goals (mainly for non-functional requirements and quality attributes) and scenarios (mainly for operational requirements, functional requirements, and performance and architectural reasoning). The goal sub-notation is called goal-oriented requirements language (GRL) and the scenario sub‑notation is called use case map (UCM).