Uses the standard UML 'Class' with the << CORBAUnion>> stereotype
CORBA Union cannot participate in generalizations or specifications
CORBA Union can not have operations
There are two ways to model CORBA Union as specified in UML Profile for CORBA:
Using a composition relationship that points to a 'switcher' and has the << switchEnd>> stereotype. Every attribute must have a tagged value with 'Case' as the key and the switch condition as the value.
Using an attribute with the << switch>> stereotype attribute acting as the 'switcher' in conjunction with a composition relationship. The navigable opposite association ends must have tagged values with 'Case' as the key and the switch condition as the value.
Please see UML Profile for CORBA v1.0 §3.5.15 for more details.