"The solution of large, complex system problems often requires great investments in time and money which may not be available. Fortunately, in these situations scientists can often use a mathematical tool, the simulation model, in order to better understand the system under investigation as well as to test proposed solutions to system problems. Modules, each representing an event (activity) of the system, are constructed and linked together to study the behavior of events including interrelationships. The behavior of an event and interrelationships is portrayed by appropriate probability distribution functions"--Introduction, paragraph 1.

National Marine Fisheries Service (NMFS)