Overview
ISO/IEC 19761:2011 defines the COSMIC functional size measurement (FSM) method for quantifying the functional size of software from a user/owner perspective. Commonly called COSMIC, the standard specifies definitions, conventions and measurement activities to produce a technology‑independent functional size expressed in COSMIC Function Points (CFP). It applies to application software, real‑time software, and hybrids, but is not intended for software dominated by complex mathematical algorithms or continuous‑variable processing (for example simulation, expert systems, audio/video processing or many game engines).
Keywords: ISO/IEC 19761, COSMIC, functional size measurement, COSMIC Function Point, software sizing, FSM.
Key topics and technical requirements
- Unit of measure: COSMIC Function Point (CFP) as the unit for functional size.
- Core concepts defined: Functional User Requirements (FUR), functional user, boundary, functional process, data group, data attribute, object of interest, layer.
- Data movement model: Measurement is based on four data‑movement BFC (Base Functional Component) types - Entry, Exit, Read, Write - each moving a single data group across boundaries or to/from persistent storage.
- Measurement activities: Stepwise activities required by the method include:
- Determination of purpose and scope of FSM
- Identification and extraction of FUR
- Identification of layers, functional users and software boundaries
- Identification of functional processes, data groups and data movements
- Classification of movements (Entry/Exit/Read/Write)
- Assignment of unit sizes and aggregation to calculate functional size
- Measurement reporting, labelling and documentation
- Aggregation & changes: Rules for aggregating CFPs per FUR and for calculating functional size of changes.
- Normative relationships: Conforms to concepts in ISO/IEC 14143‑1 and is consistent with measurement process guidance (e.g., ISO/IEC 15939).
Keywords: data movement, functional process, Functional User Requirements, CFP aggregation, measurement reporting.
Applications and users
- Who uses it: Software suppliers, customers, project estimators, QA teams, productivity analysts and organizations that need a vendor‑ and technology‑independent measure of functional size.
- Practical applications:
- Cost and effort estimation and bid preparation
- Benchmarking supplier performance and productivity
- Scope definition for contracts and maintenance
- Measuring functional change impact over releases
- Comparing productivity across technologies (business apps vs. real‑time systems)
Keywords: software estimation, benchmarking, project costing, scope measurement.
Related standards
- ISO/IEC 14143‑1: Concepts and terms for functional size measurement (referenced for definitions).
- ISO/IEC 15939: Software measurement process guidance.
- ISO/IEC 19761:2011 is the second edition (revising ISO/IEC 19761:2003) and reflects COSMIC method evolution.
Using ISO/IEC 19761 (COSMIC) helps organizations achieve consistent, repeatable functional sizing for better estimation, control and benchmarking of software projects.
