code: public void setRoot(int root)
    {
  
      super.setRoot(root);
  
    	m_exprObj = FilterExprIteratorSimple.executeFilterExpr(root, 
    	                  m_lpi.getXPathContext(), m_lpi.getPrefixResolver(), 
    	                  m_lpi.getIsTopLevel(), m_lpi.m_stackFrame, m_expr);
  
    }
docs: Set the root node of the TreeWalker.
  
  @param root non-null reference to the root, or starting point of
  the query.