Definition
ISO/IEC 9126 is an international standard that defines a quality model for software products, along with associated metrics and guidelines for evaluating software quality. The standard provides a framework for specifying, measuring, and assessing the quality of software based on a set of well‑defined attributes.
Overview
Published jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), ISO/IEC 9126 was first released in 1991 and subsequently revised, with the most widely referenced version being ISO/IEC 9126‑1:2001. The standard is divided into four parts:
- ISO/IEC 9126‑1 – Quality model (defines six primary quality characteristics).
- ISO/IEC 9126‑2 – External metrics (methods for measuring the quality characteristics from the user’s viewpoint).
- ISO/IEC 9126‑3 – Internal metrics (measures based on the software’s internal structure, e.g., code).
- ISO/IEC 9126‑4 – Quality in use metrics (focuses on the effectiveness, efficiency, satisfaction, and freedom from risk experienced by the end user).
The standard is intended for use by software developers, quality assurance professionals, and procurement organizations to facilitate objective comparison of software products and to guide quality improvement initiatives.
Etymology / Origin
The designation “ISO/IEC” denotes the joint authorship of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). The numeric code “9126” is part of ISO’s sequential numbering system for standards and does not carry intrinsic meaning beyond its identification within the ISO catalogue. The standard was developed by the ISO/IEC Joint Technical Committee 1 (JTC 1), Subcommittee 2 (SC 2) on Information Technology, which focuses on software and system engineering.
Characteristics
| Primary Characteristic | Description |
|---|---|
| Functionality | Suitability, accuracy, interoperability, compliance, and security of the software in fulfilling its intended tasks. |
| Reliability | Maturity, fault tolerance, recoverability, and availability of the software under specified conditions. |
| Usability | Understandability, learnability, operability, attractiveness, and user error protection. |
| Efficiency | Time behavior (performance) and resource utilization (e.g., memory, CPU). |
| Maintainability | Analyzability, changeability, stability, testability, and modularity of the software. |
| Portability | Adaptability, installability, conformance, replaceability, and interoperability across different environments. |
Each characteristic is further broken down into sub‑characteristics, and the standard defines quantitative and qualitative metrics for assessing them. The model is hierarchical: quality characteristics → sub‑characteristics → metrics → measurement procedures.
Related Topics
- ISO/IEC 25010 – The successor to ISO/IEC 9126, part of the SQuaRE (Software Product Quality Requirements and Evaluation) series, which refines the quality model and introduces additional characteristics such as security and compatibility.
- Software Quality Assurance (SQA) – Practices and processes that aim to ensure software meets defined quality standards, often using ISO/IEC 9126 as a reference framework.
- Metrics and Measurement in Software Engineering – The broader field concerning the definition, collection, and analysis of quantitative data about software products and processes.
- ISO/IEC 12207 – International standard for software life cycle processes, frequently used in conjunction with ISO/IEC 9126 for comprehensive quality management.
- CMMI (Capability Maturity Model Integration) – A process improvement framework that, while not a direct standard for product quality, addresses many of the same concerns as ISO/IEC 9126 at the organizational level.
