 A related question is whether or not our mathematical models are simulating target systems or merely mimicking their behavior. To be simulating a system suggests that there is some actual correspondence between the model and the target system it is designed to capture. On the other hand, if a mathematical model is merely mimicking the behavior of a target system, there is no guarantee that the model has any genuine correspondence to the actual properties of the target system. The model merely imitates behavior. These issues become crucial for modern techniques of building nonlinear dynamical models from large time series data sets (e.g., Smith 1992), for example the sunspot record or the daily closing value of a particular stock for some specific period of time. In such cases, after performing some tests on the data set, the modeler sets to work constructing a mathematical model that reproduces the time series as its output. Do such models only mimic behavior of target systems? Where does realism come into the picture? 