Simulation models & their changes are discussed. The models are divided in 3 groups: (1) man-machine models, (2) machine models, & (3) man models. Man-machine model dissatisfactions lead to more extensive & expensive possibilities. The machine model--computer simulation--is popular for practical & theoretical research. These models do not give answers to concrete questions or they assume more regularity in the system than really exists. Man-models include 'frame-games' & the 'nexus model', consisting of a framework of empty tables; up to 80 variables can be manipulated & a game-model can originate. 'Nonsimulation games' are designed to ease problems in teaching mathematics & computer languages. Validity of a model is determined by the objective from which the model is designed & used. Simulation models have the ability to predict; not to produce proof. It is necessary for specialists to understand the limitations of model simulation. 1 Figure. N. Hirschsohn.
