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Initial Publication Date: December 21, 2006

What is a Model?

Definition quoted from Modeling Methodology for Physics Teachers ( This site may be offline. ) (1997).

A model is a representation of structure in a physical system and/or its properties. It describes (or specifies) four types of structure, each with internal and external components:

  • systemic structure specifies
    • composition (internal parts of the system)
    • environment (external agents linked to the system)
    • connections (external and internal causal links)
  • geometric structure specifies
    • position with respect to a reference frame (external geometry)
    • configuration (geometric relations among the parts)
  • temporal structure specifies change in state variables (system properties)
    • descriptive models represent change by explicit functions of time
    • causal models specify change by differential equations with interaction laws
  • interaction structure specifies interaction laws expressing interactions among causal links, usually as function of state variables