An Empirical Study on the Structural Complexity Introduced by Core and Peripheral Developers in Free Software Projects

Background: Several factors may impact the process of software maintenance and evolution of free software projects, including structural complexity and lack of control over its contributors. Structural complexity, an architectural concern, makes software projects more difficult to understand, and consequently more difficult to maintain and evolve. The contributors in a free software project exhibit different levels of participation in the project, and can be categorized as core and peripheral developers. Research aim: This research aims at characterising the changes made to the source code of 7 web server projects written in C with respect to the amount of structural complexity added or removed and the developer level of participation. Method: We performed a observational study with historical data collected from the version control repositories of those projects, recording structural complexity information for each change as well as identifying each change as performed by a core or a peripheral developer. Results and conclusions: We have found that core developers introduce less structural complexity than peripheral developers in general, and that in the case of complexity-reducing activities, core developers remove more structural complexity than peripheral developers. These results demonstrate the importance of having a stable and healthy core team to the sustainability of free software projects.