Refactoring--Does It Improve Software Quality?

Software systems undergo modifications, improvements and enhancements to cope with evolving requirements. This maintenance can cause their quality to decrease. Various metrics can be used to evaluate the way the quality is affected. Refactoring is one of the most important and commonly used techniques of transforming a piece of software in order to improve its quality. However, although it would be expected that the increase in quality achieved via refactoring is reflected in the various metrics, measurements on real life systems indicate the opposite. We analyzed source code version control system logs of popular open source software systems to detect changes marked as refactorings and examine how the software metrics are affected by this process, in order to evaluate whether refactoring is effectively used as a means to improve software quality within the open source community.