[Attribute Name] REFERENCE [Type] String [#] 0 or 1 [Description] 
BINDING TYPE="Output": Any valid object reference defined by the specified Object Model. Identifies a property (typically the value) of an HTML document object to be assigned to the associated program output variable. If the identified object is not present in the output document, or the specified property is not valid for the object, null is assigned into the program output variable.