Functional Size Measurement applied to UML-based user requirements

There is a growing interest in applying standardized methods for Functional Size Measurement (FSM) to Functional User Requirements (FUR) based on models in the Unified Modelling Language (UML). No consensus exists on this issue. We analyzed the demands that FSM places on FURs. We propose a requirements space with several levels of refinement, and show how UML can be used to specify FURs at these levels. FSM can be applied at the product level of UML-based FURs. We discuss our experience for three case studies and with two FSM methods: Function Point Analysis (FPA) and COSMIC-Full Function Points (CFFP).