Consistency in model integration

State-of-the-art systems engineering uses many models reflecting various aspects of the modeled system. A major task of system engineers is to ensure consistency between the many models. We present an approach to the engineering of complex systems based on the modeling of use cases and object life cycles as Petri nets. Synchronization by place fusion allows the derivation of an integrated model that can be verified and validated. We illustrate our approach by a case study.