code: public XObject execute(XPathContext xctxt, boolean destructiveOK) 
    	throws javax.xml.transform.TransformerException
    {
    	XNodeSet xns = (XNodeSet)super.execute(xctxt, destructiveOK);
    	DTMManager dtmMgr = xctxt.getDTMManager();
    	int context = xctxt.getContextNode();
    	if(dtmMgr.getDTM(xns.getRoot()).getDocument() != 
    	   dtmMgr.getDTM(context).getDocument())
    	{
    		Expression expr = (Expression)xns.getContainedIter();
    		xns = (XNodeSet)expr.asIterator(xctxt, context);
    	}
    	return xns;
    }
docs: Dereference the variable, and return the reference value.  Note that lazy
  evaluation will occur.  If a variable within scope is not found, a warning
  will be sent to the error listener, and an empty nodeset will be returned.
  
  
  @param xctxt The runtime execution context.
  
  @return The evaluated variable, or an empty nodeset if not found.
  
  @throws javax.xml.transform.TransformerException