title: UML Class diagram: difference between Navigation and Ownership
body: <p>I read the posts in</p>
  <ul>
  <li><a href="https://stackoverflow.com/questions/18813549/association-owned-by-classifier-and-association-owned-by-relationship-in-uml">association owned by classifier and association owned by relationship in UML</a></li>
  <li><a href="https://stackoverflow.com/questions/18932674/setting-the-association-end-ownership-in-uml-what-does-it-mean-with-respect-to">Setting the association end ownership in UML: What does it mean with respect to generated code in visual paradigm (or in other UML tools)?</a></li>
  <li><a href="http://www.uml-diagrams.org/association.html" rel="nofollow noreferrer">http://www.uml-diagrams.org/association.html</a></li>
  </ul>
  <p>but the difference between &quot;navigation&quot; and &quot;ownership&quot; of associations of UML class diagrams is still unclear to me. Moreover, UML 2.5 was released in the meantime.</p>
  <p>The specification states the following:</p>
  <blockquote>
  <p>Association ends owned by classes are always navigable, while those
  owned by associations may be navigable or not.</p>
  </blockquote>
  <ol>
  <li><p>This means, that the example c below is invalid. Examples a and b are valid, in both cases the right end is navigable. However, in example b the left end is not navigable.</p>
  <p>Am I right?</p>
  </li>
  <li><p>What is the semantic difference between navigation and ownership? Is navigation a &quot;generic&quot; way of accessing the opposite class while ownership enforces a class to have an attribute?</p>
  </li>
  </ol>
  <p><a href="https://i.stack.imgur.com/WXfnp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WXfnp.png" alt="enter image description here" /></a></p>