title: How to render a component only if another component is not rendered?
body: <p>I have a page that the user can access via Android, iPhone, BlackBerry or via an unknown browser. I have 4 <code>rich:panel</code>s, one for each platform and the latter is a generic one.</p>
  
  <p>The code:</p>
  
  <pre><code>&lt;rich:panel id="dlAndroid" rendered="#{fn:containsIgnoreCase(request.getHeader('User-Agent'), 'Android')}"&gt;
      ...
  &lt;/rich:panel&gt;
  
  &lt;rich:panel id="dlIphone" rendered="#{fn:containsIgnoreCase(request.getHeader('User-Agent'), 'iPhone')}"&gt;
      ...
  &lt;/rich:panel&gt;
  
  &lt;rich:panel id="dlBlackberry" rendered="#{fn:containsIgnoreCase(request.getHeader('User-Agent'), 'BlackBerry')}"&gt;
      ...
  &lt;/rich:panel&gt;
  
  &lt;rich:panel id="dlGeneric" rendered="#{ ---&gt; WHAT TO WRITE HERE? &lt;--- }"&gt;
  </code></pre>
  
  <p>How can I render the last <code>rich:panel</code> only if none of the others has been rendered?</p>