Properties are each of a certain data type.
If a property is constrained to a property of a different data type, or is set to a constant which is not a member of the property's data type, an error will occur. Boolean Command Enumeration Event Float Integer Object String Boolean Either true or false . Booleans figure heavily in conditional statements, and also as flags for certain properties. Commands can not be referenced in an expression, they may only be asked to go. However, the expression they are assigned must have a reference to some event, so that the command will be carried out when the event happens.