UMLR — Section: 7.3.3

There is actually two closely related issues I would like to report. One is an (as I understand it) error related to figure 7.20 and the other is a humble request to enhance the documentation by more explicitly clarifying the semantics of association ends that are owned by an end class. Starting with the (possible) error. According to the specification (page 39) "An end property of an association that is owned by an end class or [...] is navigable from the opposite ends; [...]" Somewhat further down in the text there is a statement saying (page 43) "Aggregation type, navigability, and end ownership are orthogonal concepts [...]" Although this may be true in terms of notation, it is clear from the first citation (and common sense) that navigability and end ownership cannot be conceptually orthogonal. Moving on to figure 7.20, the first relation demonstrates this supposed orthogonality by showing a relation where the end connected to B is owned by A, but not navigable from A. I understand that this part might have been written with notation in mind; to demonstrate the orthogonality of the notational elements. It might, however, be considered bad practice to show notational examples that are inconsistent with the rest of the specification. The second "issue" is related to the concept of a property that is an association end owned by an end class. It took me quite some time and a lot of re-reading to understand that the "end class" was a of a different type than the type of the property. The only real hint about this was the last statement on a paragraph in on page 42 (in the notation section) stating that "This property is owned by the classifier at the other end." Since the whole concept of ownership seems a little vague, it might be a good idea to include a paragraph detailing this fact in the description of the semantics of associations. I hope this might be of some use.