The Squale Model – A Practice-based Industrial Quality Model

ISO 9126 promotes a three-level model of quality (fac-tors, criteria, and metrics) which allows one to assess qual-ity at the top level of factors and criteria. However, it is dif-ficult to use this model as a tool to increase software quality. In the Squale model, we propose the adjunction of prac-tices as an intermediate level between metrics and crite-ria. Practices abstract from raw information at the source (metrics, tool reports, audits) to provide the developer with technical guidelines to respect. Moreover, practice marks can be adjusted using formulae to suit company develop-ment habits or exigences: for example bad marks can be stressed to point to places which need the most attention. Dashboards allow one to spot faulty practices and find the source elements responsible for the bad marks. The Squale model has been developed and validated over the last cou-ple of years in an industrial setting with Air France-KML and PSA Peugeot-Citroën. Over 100 projects with a total of more than seven millions lines of code have been assessed and steered using Squale.