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Many special purpose simulators exist to simulate very specific types of systems. For example, tools exist for simulating the movement of water (and contaminants) in an estuary, the evolution of a galaxy, or the exchange rates for a set of currencies. The key attribute of these tools is that they are highly specialized to solve a particular type of problem. In many cases, these tools require great subject-matter expertise to use. In other cases, however, the system being simulated may be so highly specified that using the tools is quite simple (i.e., the user is presented with a very limited number of options).
Other tools are not specialized to a particular type of problem. Rather, they are "tool kits" or general purpose frameworks for simulating a wide variety of systems. There are are variety of such tools, each tailored for a specific type of problem. What they all have in common, however, is that they allow the user to model how a system might evolve or change over time. Such frameworks can be thought of as high-level programming languages that allow the user to simulate many different kinds of systems in a flexible way. We provide below a brief overview of how GoldSim differs from three of the most common types of general purpose simulation frameworks: discrete event simulators, system dynamics programs, and spreadsheets.
Discrete Event Simulators
Discrete simulators (such as ProModel, Arena, Extend, and Witness) generally rely on a transaction-flow approach to modeling systems. Models consist of entities (units of traffic), resources (elements that service entities), and control elements (elements that determine the states of the entities and resources). Discrete simulators are generally designed for simulating detailed processes such as call centers, factory operations, and shipping facilities.
GoldSim differs from most discrete simulators in the following manner:
System dynamics software (such as Stella, iThink, Vensim, and Powersim) is based on the standard stock and flow approach developed by Professor Jay W. Forrester at MIT in the late 1950s and early 1960s. Models based on system dynamics are built using three principal element types (stocks, flows, and converters), and put emphasis on understanding the feedback structure of systems. System dynamics software packages are typically used for simulating business and organizational systems and simple engineering and scientific systems.
Although GoldSim is similar to system dynamics programs in many ways (and can simulate any kind of system that these tools can), GoldSim moves beyond the relatively restrictive stock and flow syntax in order to more realistically model complex systems. In particular, GoldSim differs from most system dynamics software packages by offering the following features:
Spreadsheets are perhaps the simplest and most broadly used general purpose simulators. Although spreadsheets are inherently limited by their structure in many ways (e.g., representing complex dynamic processes is difficult, they cannot display the model structure graphically, and they require special add-ins to represent uncertainty), because of the ubiquity of spreadsheets, they are very widely used for simple simulation projects (particularly in the business world).
Probabilistic spreadsheet programs (such as @RISK and Crystal Ball) are add-in programs for Microsoft Excel that allow users to define probabilistic distributions for input parameters. Any type of system that can be represented in a spreadsheet can be simulated using probabilistic spreadsheet programs. One advantage of these programs compared with all other classes of simulation software is that most users are already familiar with spreadsheet programs.
GoldSim differs from probabilistic spreadsheet software in the following manner:
A more detailed discussion of the advantages of GoldSim over spreadsheets can be found here.
Note that GoldSim supports seamless integration with existing spreadsheet models via a specialized element that allows the user to dynamically pass data to and from a spreadsheet during a simulation.