ABSTRACT
A model of a system is a representation, or abstraction, of the real world being studied. System models can be used to gain an understanding of real-world complexities and can be the basis for development of support systems, such as decision aids, user interfaces, and training systems. Models can help predict performance of a system and can aid in identifying the information needed for decision-making processes concerned with system operation and design. Models are critical in the system design phase, and often valuable for system management. Models can be either descriptive (e.g. simulations that predict values of performance measures for a given input specification) or prescriptive (e.g. linear programming methods that specify the values of the decision variables that provide the normative solution for a given problem).
