title: XPATH expression that Matches on the attribute value "true"
body: <p>I have some XML like this:</p>
  
  <pre><code>&lt;engine-set&gt;
    &lt;engine host-ref="blah1.com"&gt;
    &lt;property name="foo" value="true"/&gt;
    &lt;property name="bar" value="true"/&gt;
   &lt;/engine&gt;
   &lt;engine host-ref="blah2.com"&gt;
    &lt;property name="foo" value="true"/&gt;
    &lt;property name="bar" value="false"/&gt;
   &lt;/engine&gt;
  &lt;/engine-set&gt;
  </code></pre>
  
  <p>I want to match on all engine elements that have a child node property with a name equal to "bar" and and value equal to "true". I'm finding the fact that "true" appears in my XML is causing my condition to always evaluate to true in an XPath expression. Is there a way around? I'm using Python and lxml.</p>
  
  <p><strong>EDIT:</strong></p>
  
  <p>My xpath expression is (that isn't working) is:
      //engine[(property/@name='bar' and property/@value="true")]</p>
  
  <p>Thanks, </p>