Software systems are subject to continuous changes to adapt to new and changing requirements. This phenomenon, known as software evolution, leads in the long term to software aging: The size and the complexity of systems increase, while their quality decreases. In this context, it is no wonder that software maintenance claims the most part of a software system's cost. The analysis of software evolution helps practitioners deal with the negative effects of software aging. With the advent of the Internet and the consequent widespread adoption of distributed development tools, such as software...