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Styles and Approaches
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- Model - representation of an item in some form other than the form in which it is to ultimately exist  
- set of equations   
 - computer program   
 - schematic diagram   
 - queuing network   
 
 - Model classification   
- Interpreted - the model defines the value of system variables for all time   
 - Uninterpreted - the system variables are undefined in the model over some interval(s) of time   
 
 - What's the purpose of interpreted models?   
- They very concisely represent the system   
 - They simulate much faster   
 - They provide a mechanism for system conceptualization