title: How to use DITA subjectSchemes?
body: <p>The subjectScheme in DITA is a suitable format for creating a taxonomy of metadata, but how should it really be used? Specifically, my question regards the following:</p>
  
  <ol>
  <li>Can it be used to represent metadata elements, or only metadata attributes? I've only seen it applied to attributes, which makes it kind of limited, since as far as I know elements are usually used for retrieval metada, i.e. not metadata used for filtering. </li>
  <li>If you could use it for elements, should the value still be in the "keys" attribute of the subjectdef?</li>
  <li>If you want to add a definition/description to a metadata value, where would you do that?</li>
  <li>Can/should you publish subjectSchemes? I've seen it suggested that it is not intended for publishing, due to its resource-only default attribute. But isn't that limiting? If you use it to create a taxonomy, surely you would also want a simple way to publish it for the benefit of the users?</li>
  </ol>