+(defattribute relational-attribute ()
+ ())
+
+(defdisplay :wrap-around ((attribute relational-attribute) object)
+ (print (cons "parent-r" *parent-relations*))
+ (dletf (((value attribute) (attribute-value object attribute)))
+ (unless (find (value attribute) *parent-relations* :test #'meta-model::generic-equal)
+ (call-next-method))))
+
+(defattribute has-a (relational-attribute)