The squale model — A practice-based industrial quality model

ISO 9126 promotes a three-level model of quality (factors, criteria, and metrics) which allows one to assess quality at the top level of factors and criteria. However, it is difficult to use this model as a tool to increase software quality. In the Squale model, we add practices as an intermediate level between metrics and criteria. Practices abstract away from raw information (metrics, tool reports, audits) and provide technical guidelines to be respected. Moreover, practice marks are adjusted using formulae to suit company development habits or exigences: for example bad marks are stressed to point to places which need more attention. The Squale model has been developed and validated over the last couple of years in an industrial setting with Air France-KLM and PSA Peugeot-Citroen.