An expression can use multiple types of data:
•Parameter value: the value that the user has entered for a parameter as described in the model.
•Variable value: the value of a cell out of a SQL statement.
•Group value: a derivative value of a cell from a SQL statement.
•Environment variables: the value of information concerning the environment.
•Resource variable: the translation of a translateable resource in the currently chosen language.
•Text: all the remaining.