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Modeling
An Overview


Prof. David Bernstein
James Madison University

Computer Science Department
bernstdh@jmu.edu

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A Definition
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A model is a description of a system (that is created to help understand the system)

Modeling Methods
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  • Physical Models:
    • Paper, clay, plastic, wood, metal, etc...
  • Conceptual Models:
    • Mathematical, computational/numerical, diagrammatic/visual/graphical, textual, etc...
Model Types
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  • Static:
    • Models of the aspects of the system that do not change (sometimes called structural)
  • Dynamic:
    • Models of how the system changes over time (sometimes called behavioral)
Importance of Modeling
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  • Some Observations:
    • Complex systems are hard to understand
    • Models can be used to make them easier to understand
  • An Example:
    • You can probably build a doghouse without a model
    • A house would be very difficult to build without a model
    • A skyscraper would be impossible to build without a model
Modeling and Software
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  • A Common Problem:
    • Start with a doghouse
    • Keep adding on until you have a skyscraper
  • What Models Provide:
    • An understanding of a system (as it is or should be)
    • A specification of a system
    • A template for construction
    • A record of the decisions that were made
Abstraction Revisited
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  • The same object/concept can be conceptualized at different levels of abstraction
  • A system that is conceptualized at a particular level of abstraction can be modeled at different levels of abstraction
Abstraction Revisited: An Example
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  • Viewing a Car as a System:
    • Low Detail - A source of emissions
    • Medium Detail - A contributor to traffic congestion at an intersection
    • High Detail - A mechanical motive device
  • Modeling a Car as a Source of Emissions
    • Low Detail - Relate the number of cars to total emissions
    • Medium Detail - Consider the number of miles and driven and the average drive cycle (e.g., EPA estimates)
    • High Detail - Consider car following behavior and engine performance
There's Always More to Learn
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