title: UML Class Diagram "can be" relationship
body: <p>I have two classes – <em>Type</em> and <em>Model</em>.</p>
  
  <p>A <em>Type</em> can be primitive, but any <em>Model</em> can be further used as a <em>Type</em>. Hence, a <em>Type</em> <strong>can be</strong> a <em>Model</em>, but <strong>doesn't have to be</strong>.</p>
  
  <p>How do I represent this using a UML Class Diagram?</p>
  
  <p>My initial idea is to also define a <em>PrimitiveType</em> and then connect that class and the <em>Model</em> class to the <em>Type</em> using a generalization, but I can't help but assume there is a better way.</p>