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ISO/IEC 14143‑1:2007 (CAN/CSA‑ISO/IEC 14143‑1‑07) — The Foundation of Functional Size Measurement
A technical guide to the concepts, essential requirements, and compliance framework for functional size measurement of software
ISO/IEC 14143‑1:2007, adopted in Canada as CAN/CSA‑ISO/IEC 14143‑1‑07, is the foundational document for the family of standards dealing with functional size measurement (FSM) of software. It establishes the overarching framework, definitions, and mandatory requirements that all FSM methods must satisfy to be considered consistent with the ISO/IEC 14143 series. This article provides a concise technical overview of the standard’s scope, core technical requirements, practical implementation guidance, and key compliance considerations for software measurement professionals.
Scope and Purpose of ISO/IEC 14143‑1:2007
The standard focuses on the definition of concepts that underpin functional size measurement. Its primary objectives are:
- To define a common vocabulary and set of fundamental principles for functional sizing across all software domains.
- To specify what constitutes a functional size measurement method (FSM method) that is consistent with the standard.
- To establish the boundary between an FSM method and the specific rules used to count functional size (e.g., IFPUG, COSMIC, or other counting practice manuals).
- To isolate the requirements that are independent of any particular counting approach, ensuring that all conformant methods can be compared on a common basis.
Importantly, the standard does not prescribe a single measurement method; rather, it provides the meta‑framework that permits multiple compliant FSM methods to coexist. It is applicable to all types of information systems, real‑time software, and embedded systems.
Scope Clarification: ISO/IEC 14143‑1 defines concepts and mandatory requirements for any FSM method, not the detailed counting rules. Those rules belong to subsequent parts of the series (e.g., Part 2 for dimensional models, Part 4 for reference models).
Fundamental Concepts and Technical Requirements
Core Definitions
The standard establishes essential terminology that every FSM practitioner must understand:
| Term | Definition per ISO/IEC 14143‑1 |
|---|---|
| Functional User Requirements (FUR) | The subset of user requirements that describe the functions the software must perform, independent of technical implementation. |
| Functional Size | A size of software derived by quantifying the functional user requirements, usually expressed in generic size units (e.g., function points). |
| Functional Size Measurement (FSM) | The process of assigning a specific numeric value to the functional size of a software item based on a defined FSM method. |
| FSM Method | A documented set of rules and procedures for performing functional size measurement, conforming to the requirements of ISO/IEC 14143‑1. |
Mandatory Requirements for Conformant FSM Methods
To claim conformance with ISO/IEC 14143‑1, a method must satisfy the following key criteria:
- Basis in FUR: The method must derive its measurement exclusively from the functional user requirements, not from technical or physical aspects.
- Independence of implementing technology: The size measured must remain the same regardless of the programming language, database system, or hardware platform.
- Repeatability and reproducibility: The method must produce consistent results when applied to the same FUR by different qualified measurers (reproducibility) and by the same measurer at different times (repeatability).
- Transparency and verifiability: The measurement process and its underlying rules must be fully documented and open to audit.
- Scale type: The method must define an appropriate scale (ordinal, interval, ratio) and, for most applications, must support additive properties of functional size.
Important: A method that violates the independence principle (e.g., by including non‑functional requirements such as performance or security as sizing factors) cannot claim conformance with ISO/IEC 14143‑1.
Example: Comparison of FSM Characteristics
The table below illustrates how two well‑known FSM methods align with the mandatory requirements of the standard.
| Requirement | IFPUG Function Point Analysis (v4.3) | COSMIC (v4.0) |
|---|---|---|
| Basis in FUR | Yes | Yes |
| Technology independence | Yes | Yes |
| Repeatability / reproducibility | Requires trained counters; acceptable with structured guidance | High repeatability due to simpler rules |
| Scale type | Ratio (but with debates about additive properties at lower levels) | Ratio – fully additive |
| Applicable domains | Management information systems, business applications | All layers of software including real‑time and embedded |
The standard does not rank methods; it only provides the criteria that a method must meet to be considered fit for purpose under the ISO/IEC 14143 umbrella.
Implementation and Application Guidelines
Selecting a Conformant FSM Method
Organizations that wish to adopt functional size measurement should first identify an FSM method that is certified as conformant to ISO/IEC 14143‑1 by a recognized body (e.g., IFPUG, COSMIC, or NESMA). Conformance assures that the method adheres to the core definitions and mandatory requirements, thereby facilitating benchmarking, estimation, and portfolio management across different projects and tools.
Tip: When implementing FSM, invest in training your teams on the concepts of ISO/IEC 14143‑1 before diving into the counting rules of a specific method. This deepens understanding and helps avoid common misinterpretations about what functional size represents.
Integration with Estimation and Project Management
Because functional size is independent of technology, it can serve as a stable input for parametric cost estimation models (e.g., COCOMO II, SEER‑SEM). The standard encourages organizations to establish correlation between functional size and effort using historical data from their own environments.
Compliance, Certification, and Auditing
How to Claim Conformance
A software measurement method can only be described as “ISO/IEC 14143‑1 conformant” if it has passed a formal conformance assessment. The assessment verifies that the method meets all mandatory requirements listed in Clause 6 of the standard. Most method owners (e.g., the Common Software Measurement International Consortium (COSMIC) and the International Function Point Users Group (IFPUG)) have already certified their methods.
Auditing an FSM Implementation
During compliance audits, examiners typically check:
- That the measurement process starts from documented functional user requirements.
- That the method’s counting rules are applied consistently and transparently.
- That the results are reproducible by an independent measurer using the same FUR.
- That no non‑functional or technical factors have been erroneously included in the size count.
Common Non‑Compliance Pitfall: Some organizations modify an FSM method by adding local rules that inadvertently introduce technology bias (e.g., weighting database complexity). Such adaptations invalidate conformance to ISO/IEC 14143‑1. Always document any deviations and, if conformance is needed, keep them separate from the core method.
Best Practice: Establish an internal measurement oversight board that reviews FSM results for consistency against the principles of ISO/IEC 14143‑1. This helps maintain credibility and ensures that software sizing remains a reliable management tool.
Frequently Asked Questions
Q: How does ISO/IEC 14143‑1 relate to Function Points?
A: ISO/IEC 14143‑1 is the conceptual standard that defines what a functional size measurement method must be. Function Point Analysis (e.g., IFPUG FPA) is a concrete implementation that complies with this standard. The standard is method-neutral; it provides the rules that any compliant method, including Function Points, must follow.
A: ISO/IEC 14143‑1 is the conceptual standard that defines what a functional size measurement method must be. Function Point Analysis (e.g., IFPUG FPA) is a concrete implementation that complies with this standard. The standard is method-neutral; it provides the rules that any compliant method, including Function Points, must follow.
Q: Is COSMIC a different standard from ISO/IEC 14143‑1?
A: COSMIC is a specific FSM method defined in ISO/IEC 19761, which itself conforms to ISO/IEC 14143‑1. While COSMIC implements the principles of Part 1, it uses a simpler measurement approach suitable for business, real‑time, and embedded software. The two standards are complementary: Part 1 provides the foundation, COSMIC provides a concrete measurement method.
A: COSMIC is a specific FSM method defined in ISO/IEC 19761, which itself conforms to ISO/IEC 14143‑1. While COSMIC implements the principles of Part 1, it uses a simpler measurement approach suitable for business, real‑time, and embedded software. The two standards are complementary: Part 1 provides the foundation, COSMIC provides a concrete measurement method.
Q: Can I create my own FSM method and claim conformance to ISO/IEC 14143‑1?
A: Yes, but you must demonstrate that your method satisfies all mandatory requirements of the standard. Typically this involves a rigorous independent conformance assessment. In practice, most organizations adopt an established method (IFPUG, COSMIC, NESMA) rather than developing a proprietary one.
A: Yes, but you must demonstrate that your method satisfies all mandatory requirements of the standard. Typically this involves a rigorous independent conformance assessment. In practice, most organizations adopt an established method (IFPUG, COSMIC, NESMA) rather than developing a proprietary one.
This article is based on the 2007 edition of the standard (CAN/CSA‑ISO/IEC 14143‑1‑07). All readers should consult the official publication for the complete normative text. Last updated: 2026.