Discovering maintainability changes in large software systems

In this paper we propose an approach to automatically discover meaningful changes to maintainability of applications developed using object oriented programming languages. Our approach consists of an algorithm that employs the values of several class-level software metrics that can be easily obtained using open source software. Based on these values, a score that illustrates the maintainability change between two versions of the system is calculated. We present relevant related work, together with the state of research regarding the link between software metrics and maintainability for object oriented systems. In order to validate the approach, we undertake a case study that covers the entire development history of the jEdit open source text editor. We consider 41 version pairs that are assessed for changes to maintainability. First, a manual tool assisted examination of the source code was performed, followed by calculating the Maintainability Index for each application version. In the last step, we apply the proposed approach and compare the findings with those of the manual examination as well as those obtained using the Maintainability Index. In the final section, we present the identified issues and propose future work to further fine tune the approach.