title: regex to match xml tags not containing other tags
body: <p>Let's say I want to look for XML like this:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;Address&gt;
      &lt;Street&gt;Windsor&lt;/Street&gt;
  &lt;/Address&gt;
  </code></pre>
  
  <p>and I do not want to match XML like this:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;Address&gt;
      &lt;Number&gt;15&lt;/Number&gt;
      &lt;Street&gt;Windsor&lt;/Street&gt;
  &lt;/Address&gt;
  </code></pre>
  
  <p>That is, <strong>I am looking for addresses where the <code>Address</code> node does <em>not</em> contain a <code>Number</code> tag.</strong></p>
  
  <p>I tried patterns like </p>
  
  <pre class="lang-none prettyprint-override"><code>&lt;Address&gt;(?!Number)&lt;/Address&gt;
  </code></pre>
  
  <p>or </p>
  
  <pre class="lang-none prettyprint-override"><code>&lt;Address&gt;.*?(?!Number).*?&lt;/Address&gt;
  </code></pre>
  
  <p>But I can't quite figure it out :-(</p>
  
  <p>Any ideas?</p>