Evaluating Maintainability with Code Metrics for Model-to-Model Transformations

Using model-to-model transformations to generate analysis models or code from architecture models is sought to promote compliance and reuse of components. The maintainability of transformations is influenced by various characteristics as with every programming language artifact. Code metrics are often used to estimate code maintainability. However, most of the established metrics do not apply to declarative transformation languages (such as QVT Relations) since they focus on imperative (e.g. object-oriented) coding styles. One way to characterize the maintainability of programs are code metrics. However, the vast majority of these metrics focus on imperative (e.g., object-oriented) coding styles and thus cannot be reused as-is for transformations written in declarative languages. In this paper we propose an initial set of quality metrics to evaluate transformations written in the declarative QVT Relations language. We apply the presented set of metrics to several reference transformations to demonstrate how to judge transformation maintainability based on our metrics.