y</code> field whose value MUST be one of</p>
<ol>
  <li><code>:info</code> things which are not actuallys fault, but issues noted during  validation;</li>
  <li><code>:minor</code> things which I consider to be faults, but which  don’t actually breach the spec;</li>
  <li><code>:should</code> instances where the spec says something SHOULD  be done, which isn’t;</li>
  <li><code>:must</code> instances where the spec says something MUST  be done, which isn’t;</li>
  <li><code>:critical</code> instances