ISO 9126 Standard Quality Factors

The ISO 9126 standard was developed, in an attempt to identify the critical quality attributes for computer software. The standard specifies six key quality attributes:

1. Functionality: The functionality of the quality is the degree to which the software satisfies the needs as suggested by the following sub-attributes: suitability, accuracy, interoperability, compliance, and security.

2. Reliability: Reliability means the amount of time the software is available for use, as suggested by the following sub-attributes: maturity, fault tolerance, and recovery ability.

3. Usability: Usability is the degree to which the software is easy to use, as suggested by the following sub-attributes: understandability, learnability, and operability.

4. Efficiency: Efficiency is the degree to which the software makes optimal use of the system resources as suggested by the following sub-attributes: time behavior, and resource behavior.

5. Maintainability: Maintainability is the easiness with which repair may be made to the software as suggested by the following sub-attributes: analyzability, changeability, stability, and testability.

6. Portability: Portability is the ease with which the software can be transposed from one environment to another as suggested by the following sub-attributes: adaptability, installability, and replaceability.

The ISO 9126 factors do not necessarily lend themselves to direct measurement. However, they do provide a worthwhile basis for indirect measures and an excellent checklist for assessing the quality of a system.