What is Discrete Simulation Systems

The great philosopher Aristotle said, “If you would understand anything, observe its beginning and its development.” Therefore, understanding simulation requires observing its history. Accordingly, simulation can be understood in many ways: “Simulation is the use of a model to represent over time essential characteristics of a system under study” (El Sheikh, 1987). Another definition is “Simulation is the imitation of the operation of a real-world process or system over time” (Banks, 1999). Simulation was known long before computers. According to Araten et al. (1992), “The first econometrics model of the United States economy was constructed by J. Tinbergen in 1939.” Later, as computers developed in the late 1950s and early 1960s, a spawn of computer simulation methodologies and approaches came to life. Computer simulation, like any industry, both affected and was affected by the development of different programming languages and computer capabilities and advances. This article will first give a background about simulation in general, then it will discuss the classical simulation methodologies. We will address the current trends in simulation by presenting currently used Java-based simulation languages. In this regard, the classical simulation methodologies discussed in this article include the three-phase approach, activity scan, process interaction, event scheduling, transaction flow approach, Petri nets, and Monte Carlo. The languages discussed are simjava, DEVSJAVA, JSIM, JavaSim (J-Sim), JavaGPSS, Silk, WSE (Web-enabled simulation environment), SLX, and SRML (simulation reference markup language). As such, this article will tackle the history of the approaches and methodologies while shedding light on the genealogy of the simulation languages.