A referential attribute identifies an Attribute whose value is the value of an identifying Attribute in one or more associated Classes.
xUML uses the definition in the Mellor-Balcer Executable UML book.
A Referential Attribute takes on the Type of some other Attribute via a Relationship formalization. A Referential Attribute is associated with an R tag and no Type on an xUML class diagram. A single Referential Attribute may participate in multiple Relationships and References.
The Type of a Referential Attribute is the Type of the referenced Identifier Attribute. If the Identifier Attribute itself is referential, then the same rule applies for that Attribute. This suggests, as one option, a recursive traversal terminated by the necessary discovery of a non-referential Identifier Attribute. Traversal from a Referential Attribute through one or more References must ultimately land on a Non-Referential Attribute. (If none is found, then there is an unresolved cycle in the M1 layer class model which must be fixed).
- Name + Class + Domain
Same as the superclass.