Measuring the progress of projects using the time dependence of code changes

Tracking the progress of a project is often done through imprecise manually gathered information, like progress reports, or through automatic metrics such as Lines Of Code (LOC). Such metrics are too coarse-grained and too imprecise to capture all facets of a project. In this paper, we mine the code changes in the source code repository and study the concept of time dependence of code changes. Using this concept, we can track the progress of a software project as the progress of a building. We can examine how changes build on each other over time and determine the impact of these changes on the quality of a project. In particular, we study whether new changes are built just-in-time or if they build on older, stable code. Through a case study on two large open source projects (PostgreSQL and FreeBSD), we show that time dependence varies across projects and throughout the lifetime of each project. We also show that there is a high linear correlation between building on new code and the occurrence of bugs.