A Source-Code Maintainability Evaluation Model for Software Products

The maintainability index (MI) has been proposed to calculate a single number which expresses the maintainability of a system. This article presents a model for evaluating the maintainability of software products. The model improves the shortcomings observed in the maintainability assessment approaches in the quality assessment models SQuaRE (ISO25000), ISO 9126, Squale and the FCM standard. Its main innovation is to take into account the importance of entities in the system when calculating the maintainability score. This implies that the same type of defect will have a different score depending on the entity presenting it. Seven experts with several years of experience evaluated the model. They confirmed the effectiveness and usability of the model. Then, we compared our model with the Squale maintainability index and the classical maintainability index. The results show no correlation between these models. The implications are that each method gives a slightly different view of maintainability.