All of the constants used with the RuleExpression classes, such as FunctionCall, comparison, operation, and so on, are actually properties of the constants class. You must always instantiate an object of the constants class to use any constants in your program.
For example, the comparison class uses a constant to test whether two operands are equal. Use the following code to create a comparison testing this:
&Comparison = create Comparison(&Constants.Comparison_Type_Equal);
All of the properties for the constants class are listed with the classes that use them.