Object Hierarchy | Related C++ Class: Expression
SIObject ProjectItem Operator Expression
An Expression object is a kind of Operator representing an animation source on a parameter which you can create with Parameter.AddExpression. Expressions in Softimage allow you to control animatable parameters through a mathematical formula, which may include references to the value of other parameters. This formula is stored as the value of the "Definition" Parameter, and it can be changed via the Object Model as shown in the example below.
If a Parameter's value is driven by an Expression then the Expression can be retrieved via the Parameter.Source property.
Since the expression object is kind of operator, you can use the Operator.InputPorts property to access the parameters from which the expression is reading. Access to port groups is also provided (since this is a kind of operator); however, the expression doesn't define port groups but will pretend it has one for easy access through the SDK (see Operator.GetNumPortGroups for more details).
• See Expression.1.js
Autodesk Softimage 2011