As is used in connection with systems engineering, a model is a qualitative or quantitative representation of a process or endeavor that shows the ef… - 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.

A model is a qualitative or quantitative representation of a process or endeavor that shows the effects of those factors which are significant for the purposes being considered. A model may be pictorial, descriptive, qualitative, or generally approximate in nature; or it may be mathematical and quantitative in nature and reasonably precise. It is important that effective means for modeling be understood such as analog, stochastic, procedural, scheduling, flow chart, schematic, and block diagrams.

In a society which is producing more people, more materials, more things, and more information than ever before, systems engineering is indispensable in meeting the challenge of complexity.

The concept of a system is not a simple or unique one. There are many different kinds of systems, and different systems may be organized and operated in different ways. As individuals we all belong to some social system, we participate in an economic system, we are the product of several educational systems, and we are members of one or more family systems. In a similar fashion, the equipment of which physical systems are made may be members of many other systems, such as electrical, mechanical, sensing, actuating, energy, materials, and/or information systems. One of the challenges to the person who engineers a system is to find the many alternative ways in which the function, the operation, and/or the equipment of concern and interest may be considered, understood, and made to perform most effectively.

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.