The idea of feature-oriented programming is to map requirements to features, concepts that can be composed to form a software product. Change-oriented programming (ChOP), in which features are seen as sets of changes that can be applied to a base program, has recently been proposed as an approach to FOP. Changes are recorded as the programmer works and can encapsulate any developer action, including the removing of code.

Before changes can be combined to form a product, it has to be verified that there are no harmful interactions between selected changes. There exists, however, no formal model of the current approach that may serve as a reference specification for ChOP implementations. In an effort to fill this gap, we propose a formal model of ChOP, which, as we will show, maps to the well-understood notion of feature diagram. Thanks to this, we can reuse a number of results in feature diagram research and apply them to ChOP.