A model is a qualitative or quantitative representation of a process or endeavor that shows the effects of those factors which are significant for th… - Harold Chestnut

A model may be pictorial, descriptive, qualitative, or generally approximate in nature, or it may be mathematical and quantitative in nature and reasonably precise.

The term closed loop-learning process refers to the idea that one learns by determining what s desired and comparing what is actually taking place as measured at the process and feedback for comparison. The difference between what is desired and what is taking place provides an error indication which is used to develop a signal to the process being controlled.

Those of us concerned with developing new technology should consider ourselves to have a major undertaking to try to meet the expanding needs of the increasing number of people in the world with its finite resources and environments constraints.

Models are used essentially for evaluation and prediction purposes as well as for the analysis and study of the different parts of the system so that the systems engineer or designer may arrive at sound engineering decisions regarding the system design.