Gen-Spec Relation Notation
Although a gen-spec relation is actually 1:1 among instances, its schema diagram must describe a set of subclass types that specialize their superclass type.
Therefore, a different link drawing style is used:
- The superclass is placed above a crossbar, and each of its subclasses is placed below the cross-bar; vertical lines connect all classes to the crossbar beween them.
- UML (but not CDIF) uses a white triangle on one link to denote the entity with the superclass role. The triangle is placed over the crossbar end of the link, as shown at right.