ISO/IEC 9126 in practice: what do we need to know?

ISO/IEC 9126 is currently one of the most widespread quality standards. In its actual form it embraces both quality models and metrics. Due to its generic nature, some of the concepts presented therein need to be refined before using the standard in a real project. In our paper, we aim at exploring which are the concepts that require being more elaborated before putting the standard to work. Specifically, with respect to the part 1 of the standard we focus on the hierarchical form of the quality entities (i.e., characteristics, subcharacteristics and attributes) that appear in quality models; we propose some criteria to distinguish among subcharacteristics and attributes; we distinguish among derived attributes and basic attributes; and we propose an extension for covering not only technical factors but also managerial and political ones. Concerning the other 3 parts of the standard (one of them currently pending of approval), we distinguish different categorization criteria of metrics (scale, type, objectivity, qualitative/quantitative) and we make explicit the rationale behind their definition with the Goal-Question-Metric approach. As a final contribution, we show the use of UML class diagrams for representing all the concepts of the standard and their relationships, and we highlight the need for having tool support for quality model development and metrics definition.