Is ownership (or rights) for a given content item represented by a Link from a User Node to the content item?
No. This semantic is represented by the Control object that is a component of a License. The Control object has byte code (the control program) within it which tests for the reachability of the target Node. The result of this test is a function of whether there is a valid path from the Personality Node (of the device attempting to play the content) to the target Node.