An empirical study of software change: origin, acceptance rate, and functionality vs. quality attributes

The paper presents results from an empirical study of change requests in four releases of a large-scale telecom system that is developed incrementally. The results show that earlier releases of the system are no longer evolved. Perfective changes to functionality and quality attributes are most common. Functionality is enhanced and improved in each release, while quality attributes are mostly improved, and have fewer changes in forms of new requirements. The share of adaptive/preventive changes is lower, but still not as low as reported in some previous studies. Data for corrective changes (defect fixing) have been reported by us in other studies. The project organization initiates most change requests, rather than customers or changing environments. The releases show an increasing tendency to accept change requests, which normally impact project plans. Changes related to functionality and quality attributes seem to have similar acceptance rates. We did not identify any significant difference between the change-proneness of reused and non-reused components.