Refactoring for changeability: a way to go?

Legacy systems are difficult and expensive to maintain due to size, complexity, and age of their code base. Business needs require continuously adding new features and maintaining older releases. This and the ever present worry about feature breakage are often the reason why the sweeping changes for reversing design degradation are considered too costly, risky and difficult to implement. We study a refactoring carried out on a part of a large legacy business communication product where protocol logic in the registration domain was restructured. We pose a number of hypotheses about the strategies and effects of the refactoring effort on aspects of changeability and measure the outcomes. The results of this case study show a significant decrease in customer reported defects and in effort needed to make changes