A quantitative evaluation of maintainability enhancement by refactoring

Program refactoring is a technique to enhance the maintainability of a program. Although the concept itself is considered to be effective, there are few quantitative evaluation of its impact to the software maintainability. It is sometimes difficult to judge whether the refactoring in question should be applied or not without knowing the effect accurately. We propose a quantitative evaluation method to measure the maintainability enhancement effect of program refactoring. We focused on the coupling metrics to evaluate the refactoring effect. By comparing the coupling before and after the refactoring, we could evaluate the degree of maintainability enhancement. We applied our method to a certain program and showed that our method was really effective to quantify the refactoring effect and helped us to choose appropriate refactorings.