ABSTRACT
This chapter introduces a set of system models in terms of which the rest of the theory will be developed. It should be pointed out that this is not the only set of models on which the theory could be based. The system receives inputs from outside the system across the boundaries. It is assumed the system has no direct control over its inputs. These inputs can be of several types received independently and simultaneously. Across the boundary of the system, the system produces outputs. An important component for modeling many types of systems, for example manufacturing systems, is the queue: People or objects are lined up in a queue to receive some kind of service. In a manufacturing system model, the queue system is a component coupled to and feeding one or more server system models which perform operations on or services for the elements of the queue.
