  When designing systems that are complex, dynamic and stochastic in nature,
simulation is generally recognised as one of the best design support
technologies, and a valuable aid in the strategic and tactical decision making
process. A simulation model consists of a set of rules that define how a system
changes over time, given its current state. Unlike analytical models, a
simulation model is not solved but is run and the changes of system states can
be observed at any point in time. This provides an insight into system dynamics
rather than just predicting the output of a system based on specific inputs.
Simulation is not a decision making tool but a decision support tool, allowing
better informed decisions to be made. Due to the complexity of the real world,
a simulation model can only be an approximation of the target system. The
essence of the art of simulation modelling is abstraction and simplification.
Only those characteristics that are important for the study and analysis of the
target system should be included in the simulation model.
