Development processes in engineering disciplines are inherently complex. Throughout the development process, the system to be built is modeled from different perspectives, on different levels of abstraction, and with different intents. Since state-of-the-art development processes are highly incremental and iterative, models of the system are not constructed in one shot; rather, they are extended and improved repeatedly. Furthermore, models are related by manifold dependencies and need to be maintained mutually consistent with respect to these dependencies. Thus, tools are urgently needed which assist developers in maintaining consistency between inter-dependent and evolving models. These tools have to operate incrementally, i.e., they have to propagate changes performed on one model into related models which are affected by these changes. In addition, they need to support user interactions in settings where the effects of changes cannot be determined automatically and deterministically. We present an algorithm for incremental and interactive consistency maintenance which meets these requirements. The algorithm is based on graphs, which are used as the data model for representing the models to be integrated, and graph transformation rules, which describe the modifications of the graphs to be performed on a high level of abstraction.
