Different "windows" into a model will have to be provided for different users, including "help"-line operators, engineers, managers, supervisors, technicians, schedulers, human resources personnel, and maintenance personnel. Each type of user will have his or her own perspective on reasons for using the model, and the model should be able to be tailored to accommodate those specific needs.
The desired coupling of a model (the virtual factory) directly to a real factory demands that changes in the real factory be quickly incorporated into the model, or, conversely, that the model be used to drive changes in the real factory.
Since models will pass information up and down the management ladder, information exchange mechanisms must be consistent. Hence, a consistent model representation language is needed that will precisely define a model's objects and the relationships between objects at different levels of abstraction.