Many software organisations have been looking for effective ways to improve software quality. The quality characteristics defined by software quality models provide a framework for specifying quality requirements. These quality requirements need to be represented in a defined quality model. The quality models like ISO/IEC 9126-1 are intended to be applicable to any type of software product or intermediate product. Before application the models need to be
tailored to a specific piece of software. Since these characteristics cannot be directly measured it is difficult to directly prioritise and choose the most relevant characteristics and sub-characteristics