title: How to query for rally stories that are not tagged?
body: <p>I have a basic dropdown that contains all the tags defined for a project and two extra fields "All" and "None". The dropdown is used to filter stories on a cardboard. I have managed to make it work for individual tags and the "All" field (to show all user stories) but am having difficulties filtering the cardboard by user stories that do not have tags associated with them.</p>
  
  <p>My cardboard config looks similar to this:</p>
  
  <pre><code>var cardboardConfig = {
      types: ['HierarchicalRequirement'],
      attribute: "ScheduleState",
      sortAscending: true,
      order: "Rank",
      fetch: "Name,FormattedID,Owner,ObjectID,Tags,Discussion",    
  };
  </code></pre>
  
  <p>For the <code>cardboardConfig.query</code>, I have some logic to generate the query that eventually looks similar to this:</p>
  
  <pre><code>'Tags contains "/tag/12345"'
  </code></pre>
  
  <p>I know <code>Tags</code> is an array containing <code>Tag</code> objects and I've written a test that showed that stories that don't have tags associated with them have an empty <code>Tags</code> array, so I tried the following to query for stories without tags but all didn't return any results:</p>
  
  <pre><code>'Tags = null'
  'Tags = []'
  'Tags contains null'
  'Tags contains ""'
  </code></pre>
  
  <p>On the net and stackoverflow, there are answers saying that Rally doesn't support <code>not contains</code> so I couldn't do the reciprocate of filtering the cardboard by all stories that have tags as well.</p>