Supporting Software-Evolution at the Process Level

The ability to be changeable is inherent to software — in fact, this is what defines it as being “soft”. The long-term management of large software systems depends on the ability of a system to be “easy” to maintain and evolve. In contrast to commonly presented views, we define three ways to look at evolvability. First, it can be considered to be a quality property, and must therefore be subject to quality control. Second, it can be handled as a non-functional requirement and must therefore be part of the requirements management and change management process. Third, one could claim that it is not the system’s ability but the ability of the development and maintenance team that allows for cost-effective maintenance cycles. This in turn requires a sound understanding of the system and its environment. This paper argues that the combination of these three different views allows for a coherent understanding of maintenance and evolution of software systems. We suggest a couple of principles how to deal with long-lived systems in a systematic fashion, and derive a development process model built on these principles.