A model is a representation of the construction and working of some system of interest. A model is similar to but simpler than the system it represents. A simulation (see simulator types) is a method for implementing a model. There are four (4) common types of models that are used. These are: [1,2]

• Physical: A physical model is a model whose physical characteristics resemble the physical characteristics of the system being modeled. A simple example of a physical model is a plastic airplane you played with in grade school. See Prototyping
• Mathematical: A mathematical model is a symbolic model whose properties are expressed in mathematical symbols and relationships. Mathematical models are commonly used to quantify results, solve problems and predict behavior. A simple example of a mathematical model is the equation that represents a straight line: y=mx+b.
• Process: Process models are designed to replicate steps in a process or system. All process models allow users to define their processes, workflows or system dynamics. Other common processes that are modeled are information flow through a system and the manufacturing of parts using an assembly line.
• Combination: The approach of combining models learned from multiple batches of data as opposed to the common practice of learning one model from all the available data (i.e., the data combination approach).

AcqLinks and References:

• Modeling & Simulation Guidance for the Acquisition Workforce – Oct 208
• DoD Instruction 5000.61 “DoD M&S Verification, Validation, and Accreditation (VV&A)” – 9 Dec 2009
• DoD 5000.59 “DoD Modeling and Simulation (M&S) Management” – 8 Aug 2007
• DoD “M&S Body of Knowledge (BOK)” – June 2008
• DAU “Test and Evaluation Management Guide” – Chapter 14 – Jan 2005
• SMC “Systems Engineering Handbook” – 15 Jan 2004
• DoD 5000.59-M “M&S Glossary” – Jan 1998
• DoD “M&S Glossary” – 1 Oct 2011
• Acquisition Modeling and Simulation Master Plan – 17 April 2006
• White Paper: JHU APL “Best Practices for the Development of M&A” – June 10
• White Paper: Introduction to Modeling and Simulation by Anu Maria
• White Paper: Introduction to Modeling and Simulation
• Presentation: Manager’s Guide to the High Level Architecture (HLA) for M&S – 11 May 2009
• Website: Air Force Agency for Modeling and Simulation
• Website: Army Modeling and Simulation Office
• Website: DoD M&S Coordination Office (MSCO)
• Website: DoD M&S Catalog
• Website: Simulate Interoperability Standards Organization (SISO)