A study of quality improvements by refactoring

Refactorings, behavior preserving transformations, are claimed to make software easier to understand and to improve software design. However, these claimed quality improvements have yet to be validated. This dissertation reports on our contributions to their validation.; First, a validation of two existing reengineering patterns that use refactoring to support program comprehension is presented. Second, we discuss the results of formal analysis of the conditions in which known refactorings improve coupling and cohesion as criteria for well-balanced object-oriented design.; The results of this research confirm that, indeed, the claimed benefits can occur, and describe how and when the application of refactoring can improve selected quality characteristics.; The integration of these results in today's refactoring tools can support maintainers in assessing which refactorings to apply where, ultimately reducing the effort of transforming towards an optimal solution.