ISO/IEC TR 9126-4:2004 provides quality in use metrics for measuring the attributes defined in ISO/IEC 9126-1. ISO/IEC TR 9126-2 defines external metrics and ISO/IEC TR 9126-3 defines internal metrics for measurement of the subcharacteristics defined in ISO/IEC 9126-1. Internal metrics measure the software itself, external metrics measure the behaviour of the computer-based system that includes the software, and quality in use metrics measure the effects of using the software in a specific context of use.

The metrics listed in ISO/IEC TR 9126-4 are not intended to be an exhaustive set. Developers, evaluators, quality managers and acquirers may select metrics from ISO/IEC TR 9126-4 for defining requirements, evaluating software products, measuring quality aspects and other purposes.

ISO/IEC TR 9126-2 is intended to be used together with ISO/IEC 9126-1.

ISO/IEC TR 9126-4 contains:

-- an explanation of how to apply software quality metrics;

-- a basic set of metrics for each characteristic; and

-- an example of how to apply metrics during the software product life cycle.

It includes as informative annexes a quality in use evaluation process and a reporting format.