UML14 — Page 54 - ConstrainedStereotype

Summary: This association is a means to define constraints to particular stereotypes, generally defined by the User. If we want to be able to let the user define constraints for every model elements, the constraint should have a " baseClass " attribute, or a specific kind of stereotype should be defined, which name is " default " or " base ", and which is the root of the stereotype inheritance tree In that case, defining a constraint for that stereotype means that a constraint for the associated metaclass is defined.

considered and declined