title: Using XPath count()
body: <p>I have simple XML file like that:</p>
  
  <pre><code>&lt;screen&gt;
      &lt;object attribute="String"/&gt;
      &lt;object attribute="Relationship"&gt;
           &lt;vertices&gt;
               &lt;vertex point_index="1" x="18" y="30" /&gt;
               &lt;vertex point_index="2" x="91" y="30" /&gt;
               &lt;vertex point_index="3" x="91" y="60" /&gt;
               &lt;vertex point_index="4" x="18" y="60" /&gt;                   
           &lt;/vertices&gt;
      &lt;/object&gt;
  &lt;/screen&gt;
  </code></pre>
  
  <p>How to correctly use XPath(1.0) count() function to receive vertices count in object with specified type? I'm trying to use the following string, but online XPath test tool (http://www.xpathtester.com/test) returns error. </p>
  
  <pre><code>count(/screen/object[@attribute="Relationship"]/vertices/*)
  </code></pre>
  
  <p>What seems to be wrong?</p>