code: protected int getNextNode()
    {
      if (null != m_exprObj)
      {
        m_lastFetched = m_exprObj.nextNode();
      }
      else
        m_lastFetched = DTM.NULL;
  
      return m_lastFetched;
    }
docs: Get the next node via getNextXXX.  Bottlenecked for derived class override.
  @return The next node on the axis, or DTM.NULL.