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BS ISO IEC 14143 — Software Functional Size Measurement Standard Series (Conformity Evaluation and Guide for Use)
Information Technology — Software Measurement — Functional Size Measurement: Conformity Evaluation and Guide for Use
📏 BS ISO/IEC 14143 is the software functional size measurement (FSM) standard series developed by ISO and IEC and adopted by the British Standards Institution (BSI) as a UK national standard. This batch includes ISO/IEC 14143-2:2011 (Conformity evaluation of software size measurement methods to ISO/IEC 14143-1) and ISO/IEC 14143-6:2012 (Guide for use of the ISO/IEC 14143 series), providing the basis for evaluating the standard conformance of function-point-type measurement methods and for their correct use.
💡 Functional size measurement measures software size in terms of “user-visible functionality”, independent of implementation language and technology — a key basis for cost estimation, productivity comparison, and contract pricing.
1. Series Overview and Positioning 📌
The ISO/IEC 14143 series revolves around functional size measurement: Part 1 defines FSM concepts and terms; Part 2 specifies conformity evaluation of measurement methods to Part 1; Part 3 verification; Part 4 reference model; Part 5 determination of functional domains; Part 6 provides the guide for use. The Part 2 and Part 6 in this batch correspond to the “evaluation” and “use” practical phases respectively.
| Standard | Title | Year | Core Content |
|---|---|---|---|
| BS ISO/IEC 14143-2:2011 | Conformity evaluation of software size measurement methods to ISO/IEC 14143-1 | 2011 | Evaluator characteristics, conformity evaluation process, and result reporting |
| BS ISO/IEC 14143-6:2012 | Guide for use of the ISO/IEC 14143 series | 2012 | Overview of FSM-related standards, standardised methods, relationships, and guidance |
⚠️ Parts 2 and 6 replace and withdraw their 2002 and 2006 editions. FSM terminology is used in conjunction with method standards such as ISO/IEC 20926 (IFPUG function points); check method-specific terms when citing.
2. Conformity Evaluation (Part 2) ✅
Part 2 specifies how to evaluate whether a software size measurement method conforms to ISO/IEC 14143-1:
- Evaluator characteristics: qualification and independence requirements for evaluation bodies and personnel.
- Evaluation process: identify the measurement method, compare against ISO/IEC 14143-1 requirements, check item by item, and form a conclusion.
- Evaluation result: produce a conformance evaluation report stating the degree of conformity of the method to the standard.
- Conformance statement: the method provider shall declare its scope of conformity and limitations.
💡 Conformity evaluation is the “passport to method standardisation”: only FSM methods that pass evaluation produce measurements with cross-organisation, cross-project comparability and credibility.
3. Guide for Use (Part 6) 📘
Part 6 provides guidance for users of FSM-related standards, mainly covering:
- Standard overview: outlines of the ISO/IEC 14143 parts and their interrelationships.
- Standardised FSM methods: overview of several standardised functional size measurement methods (e.g. function-point-type methods).
- Relationships between standards: the dependencies and references among FSM-related standards.
- Guidance for use: concrete guidance for correctly selecting and using FSM methods.
| Topic | Content | Beneficiary |
|---|---|---|
| Standard overview | Outlines of the series parts | Method users |
| Standardised methods | Overview of mainstream FSM methods | Measurement practitioners |
| Standard relationships | Dependencies and references | Implementers |
| Guidance for use | Selection and use guidance | Managers, estimators |
4. Key Technical Requirements ⚙️
- FSM methods shall measure per the functional-size concepts defined in ISO/IEC 14143-1.
- Method providers shall pass conformity evaluation and declare their scope of conformity.
- Measurement results shall be repeatable and comparable, keeping a consistent basis for cost estimation and productivity analysis.
- Users shall follow the Part 6 guidance to select a method suited to their functional domain and measurement purpose.
⚠️ Functional size is not code size: FSM measures user-perceivable functionality, not lines of code. Confusing the two leads to estimation error, especially where technology selection and language differences are significant.
5. Engineering Practice 🛠️
- Software cost estimation: model effort and cost using functional size as input.
- Productivity comparison: compare team and project efficiency with metrics such as functional size per person-hour.
- Contract pricing: use functional size as the pricing and acceptance baseline for outsourcing contracts.
- Method selection: evaluate and select a suitable function-point measurement method per the guidance.
6. Frequently Asked Questions ❓
❓ Q: What is functional size measurement (FSM)?
A: FSM measures software size by user-visible functionality, independent of implementation language and technology — suited to cost estimation, productivity comparison, and contract pricing.
A: FSM measures software size by user-visible functionality, independent of implementation language and technology — suited to cost estimation, productivity comparison, and contract pricing.
❓ Q: What does Part 2 specify?
A: Part 2 specifies conformity evaluation of measurement methods to ISO/IEC 14143-1, including evaluator characteristics, the evaluation process, and result reporting.
A: Part 2 specifies conformity evaluation of measurement methods to ISO/IEC 14143-1, including evaluator characteristics, the evaluation process, and result reporting.
❓ Q: What is the role of Part 6?
A: Part 6 provides the guide for use of the FSM series, including standard overviews, overviews of standardised methods, inter-standard relationships, and selection/use guidance.
A: Part 6 provides the guide for use of the FSM series, including standard overviews, overviews of standardised methods, inter-standard relationships, and selection/use guidance.
🔍 Q: How does functional size differ from code size?
A: Functional size measures user-perceivable functionality; code size measures implementation lines. The two do not correspond directly, and confusing them causes estimation error.
A: Functional size measures user-perceivable functionality; code size measures implementation lines. The two do not correspond directly, and confusing them causes estimation error.