Simulation and Modeling of Systems of Systems

Chapter 4

Modeling Systems and Their Environment 1

4.1. Introduction

A typical simulation architecture shows different categories of models that are found within a simulation (Figure 1.7):

– models of the system itself,

– models of the system environment, and

– models of human behavior, typically that of system operators.

It would not be possible to go into detail on these different models here, as there are a number of possibilities depending on the goal and the technical choices made, and our purpose here is not to give an exhaustive presentation of the modeling of all imaginable types of system because it would require a work of thousands of pages. However, it is essential to have a concrete understanding of modeling activity to be aware of the constraints imposed by specific types of model. Therefore, we provide an overview of some of the main techniques used to model time, physical laws, random processes, human behavior, and the natural environment.

If the reader wishes to study any of these subjects in more detail, a selection of published literature on the subject is available, and the contents of the bibliography of this chapter would be a good starting point.

4.2. Modeling time

Time is a fundamental variable in a simulation. It determines the evolution of state variables (e.g. the position of an object depends on its velocity and time) and is an event trigger (e.g. release of a bomb at instant t).

Time, at least in the real world, is a continuous variable1. Nevertheless, ...