  Services for Cyber-Physical Systems based on Artificial Intelligence and
Machine Learning require a virtual representation of the physical. To reduce
modeling efforts and to synchronize results, for each system, a common and
unique virtual representation used by all services during the whole system
life-cycle is needed, i.e. a DigitalTwin. In this paper such a DigitalTwin,
namely the AI reference model AITwin, is defined. This reference model is
verified by using a running example from process industry and by analyzing the
work done in recent projects.
