A Reference is an Attribute whose value is contained either in part or completely within another attribute. The attribute being referenced must be within the scope and not another reference. The built-in attribute being referenced must be persistent. The Reference can only be accessed through a presentation (not from logic). A Reference attribute is also a part of the structure of the owning class.

The typical use of a Reference is to present a cell of an array. The association to another object is contained in the expression Constraint. This expression represents a path to the referenced attribute.

An internal relationship is established between the referenced attribute and the Reference when the expression in the Constraint property of the Reference is validated and a Use dependency exists. The expression is parsed using the validation of the owner.

The Constraint property of the Reference must be validated before the Direction property is available for placing the object in the presentation of the owner. In order to use a Reference in a presentation, the PresentationType property of the owner must be set to a value other than None.

Refer to Reference Properties for properties applicable to References.