“Abstract mathematical models might be thought of as attempts to use a general-purpose and precise framework to represent dependence relationships that might exist between the parts of real systems. A mathematical model will treat one variable as a function of others, which in turn are functions of others, and so on. In this way, a complicated network of dependence structures can be represented. And then, via a commentary, the dependence structure in the model can be treated as representing the dependence structure that might exist in a real system.”