Taxa and super taxa of schema evolution and their relationship to activity, heartbeat and duration

In this paper, we present the findings of a large study of the evolution of the schema of 195 Free Open Source Software projects. We identify families of evolutionary behaviors, or taxa, in FOSS projects. A large percentage of the projects demonstrate very few, if any, actions of schema evolution. Two other taxa involve the evolution via focused actions, with either a single focused maintenance action, or a large percentage of evolution activity grouped in no more than a couple interventions. Schema evolution also involves moderate, and active evolution, with very different volumes of updates to the schema. We also investigate how the different taxa relate to measurable properties of schema evolution, specifically, duration of schema and project updates, activity volume, and heartbeat. We show that although different taxa have practically very similar duration, the evolutionary characteristics differ in analogy to the "active" character of each taxon. Moreover, by observing certain similarities in the measurable properties of the taxa, we take the opportunity to introduce super taxa, which complement the previous taxonomy with the groupings of the aforementioned taxa in terms of overall profile similarity, resulting in a more concise and intuitive taxonomy, providing a cleaner separation of evolution measures. Finally, we show that schema evolution is frequently, a time-concentrated activity. (c) 2022 Elsevier Ltd. All rights reserved.