ABSTRACT
In Chapter 2, a system was defined as a set of components or activities that interact to achieve a desired task. The primary requirement to study a system, be it a chemical plant or a flight vehicle, is a model that closely resembles the system. In other words, a model is a simplified representation of a system that helps to understand, predict, and possibly control its behavior. It presents a workable knowledge of the system and simulates its behavior. Some authors also refer to a model as a less complex form of reality.
