The evolution of Java']Java build systems

Build systems are responsible for transforming static source code artifacts into executable software. While build systems play such a crucial role in software development and maintenance, they have been largely ignored by software evolution researchers. However, a firm understanding of build system aging processes is needed in order to allow project managers to allocate personnel and resources to build system maintenance tasks effectively, and reduce the build maintenance overhead on regular development activities. In this paper, we study the evolution of build systems based on two popular Java build languages (i.e., ANT and Maven) from two perspectives: (1) a static perspective, where we examine the complexity of build system specifications using software metrics adopted from the source code domain; and (2) a dynamic perspective, where the complexity and coverage of representative build runs are measured. Case studies of the build systems of six open source build projects with a combined history of 172 releases show that build system and source code size are highly correlated, with source code restructurings often requiring build system restructurings. Furthermore, we find that Java build systems evolve dynamically in terms of duration and recursive depth of the directory hierarchy.