ODATA-1232 proposed supporting "union types" by restricting the set of types derived from a common type. In processing ODATA-1232, we discovered that we already had an annotation term, DerivedTypeConstraint, for restricting the set of derived types.

The DerivedTypeConstraint annotation term was originally added in ODATA-1034 to restrict the set of primitive types supported for a property or type definition. While it makes sense to use the same term for other constraints on derived type, we neglected to add those other targeted elements to the AppliesTo list.