Longitudinal Evaluation of Software Quality Metrics in Open-Source Applications

Assessment of software quality remains the focus of important research efforts, with several proposed quality models and assessment methodologies. ISO 25010 describes software quality in terms of characteristics such as reliability, security or maintainability. In turn, these characteristics can be evaluated in terms of software metric values, establishing a relation between software metrics and quality. However, a general metric-based model for software quality does not yet exist. The diversity of software applications, metric definitions and differences between proposed quality models all contribute to this. Our paper proposes a longitudinal evaluation of the metric values and their relations in the context of three complex, open-source applications. We cover the entire 18 year development history of the targeted applications. We explore typical values for metrics associated with software product quality and explore their evolution in the context of software development. We identify dependant metrics and explore the effect class size has on the strength of dependencies. At each step, we compare the obtained results with relevant related work in order to contribute to a growing pool of evidence towards our goal - a metric-based evaluation of software quality characteristics.