Investigating Software Maintainability Development: A case for ISO 9126

Software maintainability has been considered as a main characteristic in many software product quality models. However, these models have different definitions for maintainability and sub characteristics. ISO 9126 is one of the main and most frequently used models in software product quality. This model has been revised and replaced by ISO 25010 as a new model of software product quality. In addition to the many modifications that were performed on ISO 9126 model, maintainability was one of the main modified characteristics. However, it was developed unclearly without any standard base, and with no clear definition or evidence of how the sub characteristics were defined and modified. This paper investigates these modifications and the differences between the definitions of the maintainability in the two models, ISO 9126 and ISO 25010. As a result of this discussion, it has been concluded that both models ISO 9126 and ISO 25010 lack of a clear definition or standard base for defining software maintainability and its sub characteristics.