title: XSD - one of 2 attributes is required?
body: <p>Is there a way to specify that one of 2 attributes is required in XSD?</p>
  
  <p>for example, I have a definition like this:</p>
  
  <pre><code>&lt;xs:attribute name="Name" type="xs:string" use="optional" /&gt;
  &lt;xs:attribute name="Id" type="xs:string" use="optional" /&gt;
  </code></pre>
  
  <p>I want to be able to define that at least one of these is required. Is that possible?</p>