ABSTRACT
The word ‘model’ is often used by scientists in addition to the word ‘theory’, and it perhaps suggests more readily the concept of an analogy, because of the more general use of the word to mean a physical model or something which represents something else. A major advantage from model-building is that models can usually be manipulated to examine alternative policies without significantly changing the real-life situation being studied. In order to construct a particular model, it may be necessary to make direct experiments on a small scale if past data is insufficient. A model is usually constructed with some specific purpose in mind, and a series of models may be necessary to represent a total system. The model-building approach is the key concept of operational research and is the reason both for its practical success and for its very wide scope at all levels.
