Software Entropy in Agile Product Evolution

As agile software development principles and methods are being adopted by large software product organizations it is important to understand the role of software entropy. That is, how the maintainability of a system may degrade over time due to continuous change. This may on one side affect the ability to act agile in planning and development. On the other side, an agile process may affect growth of entropy. We report from a case study of a successful software product line organization that has adopted the agile development method Evo, showing how agility and entropy are negatively related. We conclude this study by suggesting a two-step approach to manage entropy while maintaining process agility. First, the system needs to be restructured to establish a level of manageable entropy, and then, that the agile process must be complemented with continuous semi-automated quality monitoring and refactoring support.