The SD Model in Depth

    Converters

A Converter is a computational model element that immediately processes constants, externally provided data, internal model values such as stock levels and flow rates, and other model variables in a user-defined formula.  The result of a converter process is a floating point or an alphanumeric string. 

Three converters types are defined for the Model Builder process:

1. •Single Function Converter is a simple floating point converter type that performs a single mathematical operation on a set of input variables presented to it
   

2. •Delayed Converter is a converter type that delays the value of a variable for a time value or number of simulation intervals
   

3. •Customized Converter is a complex converter type that computes any configured multifunction calculation on any number of input variables and delays the result if configured to
   

The converter symbol is a stylized circle.  The following are converter symbols:

Attributes configured by the Model Builder user for any converter:

1. •GRAPHTABLE - display the simplest possible graph and table of RESULT; a value of “NO” (default) or “YES”
   

2. •GRAPH - display a high quality formatted graph of RESULT; a value of “NO” (default) or “YES”
   

3. •TABLE - display a high quality formatted table of RESULT; a value of “NO” (default) or “YES”
   

4. •ABSTRACT - publish RESULT to abstraction layers; a value of “NO” (default) or “YES”
   

Attributes configured by the Model Builder user for a simple converter:

1. •FORMULA - the formula to calculate the converter’s result
   

2. •SHOW VARIABLES - show implicit user input variable and result variable lines and labels on the converter symbol; a value of “NO” (default) or “YES”
   

Attributes configured by the Model Builder user for an delayed converter:

1. •DELAY INITIAL - the converter’s initial delay value
   

2. •DELAY FORMULA - the formula to calculate the converter’s delay value
   

The attributes of the customized converter are a “superset” of attributes including those of the simple converter for one or more operations and the delayed converter defined above. 

Component Interfaces on an converter allowed by the Model Builder process:

1. •from or to a modeled stock, a modeled flow, a transformer, a converter of a factory as an internal variable value
   

2. •from an external variable, an adjusted variable or a user-input variable
   

Error Conditions detected and prohibited by the Model Builder process:

1. •positive or negative infinity (largest number) or smallest number (not zero)
   

Other Behaviors and Characteristics:

1. •the simple converter symbol shows the operation performed by the converter
   

2. •the formula for a summed or multiplied converter is trivial and built automatically as operand variable connections are made to the converter
   

System Dynamics Calculator  ⇑

The SD Model in Depth  ↑

Variables →

        System Dynamics Calculator

                The Calculator

                The SD Model in Depth

                        Stocks

                        Flows

                        Transformers

                        Converters

                        Variables

                        Factories

                        Customized Factory Packages

                        Abstraction Layers, Fragments and Scripts

                        Functions

                The Model Builder

                The Model Simulator

                Appendix: The Modeling Process

                System Dynamics CalculatorR1.pdf

                SD2ProjectProposalSDS.pdf