3.3 Types of quantitative systems model

There is a wide range of quantitative models, of varying degrees of sophistication and complication. In this pack, we will only cover those that I think you are likely to encounter in systems studies or could use to good effect. The techniques available subdivide broadly into two major classes, static models and dynamic models. The distinction between these will become clearer as you look at some detailed examples. Essentially, dynamic models are those where the set of calculations comprising the model is repeated a number of times. The initial values of the variables in the current set of calculations are taken from the results of the previous set of calculations, and this process is repeated time and time again. In static models, the calculations are executed once to obtain a result (or set of results). Even where the calculations are repeated, as with stochastic models, the values in each set of calculations is not determined by the previous calculation.

Table 1 gives a list of techniques, under these two broad headings.