UMLR — Properties on Association for end objects

The memberEnd/ownedEnd/NavigableOwnedEnd properties of Association represent the navigations from one end object to other end objects along the association. There are no properties available for navigating from an instance of an association (link) to the end objects. This has a number of negative effects: - The model cannot represent structured associations properly, because association classes that are also structured classifiers cannot have connectors to end objects, because the end objects cannot be reached with StructuredClassifier.role (see constraint 3 on Connector). - An InstanceSpecification for link can use memberEnd properties of association as properties of the link, even though these properties are ownedAttribute of the end classes, rather than the association. This is due to the loose definition of Classifier.allFeatures. - A special action is needed to retrieve (the end objects of links (ReadLinkObjectEndAction), rather than (using the action for attribute values ReadStructuralFeatureAction. The metamodel should have an association for properties that have the end objects of link objects as values.