An expression provides a value based on an evaluation of the names, constants, and symbols in the expression. Some expressions provide a numeric value; these are called numeric expressions. Others provide a true/false value; these are called Boolean expressions.
Expressions allow you to introduce variability into your model. They let you track, control, and respond to events. To create an expression you may use any combination of constants, probability distributions, attributes, and variables. These elements allow you to expand the scope and improve the credibility of your model.
This section shows you how to create expressions and how to use distributions, attributes, and variables in your model to accurately reflect the variability and randomness of the real world.