3.2 SUMMARY

In this chapter, the basics of model building were explained in detail. This explanation was supported by a demonstration of the graphical integration method. The results of graphical integration method and model building using Powersim™ Studio were found to agree fully. In comparing the two methods it was found that small errors are introduced by the numerical method used by system dynamics modelling software. It was explained that these errors can be minimised by careful choice of dt and method and order of integration used. Whilst the model developed does not include feedback it does include constraints on each of the rates in the model and the state variable. As is invariably the case, building system dynamics models starts with simple models. With successive iterations, complexity is added until a necessary and sufficient representation of the problem has been created. The model is progressively verified. In subsequent chapters, the basics of model building are extended and model verification and validation are explained in detail.