???????????8????????????
???2??????????????21?? (??????? ?)21??????????,?????8????
?,??????????,????????,????????????4?????????4?????,??????????????????????????,???????????????????“??????????????????????”??????????????????????????,??????????????????????????,????????????
??????,???????,?????????,?????????????????“????”???“1+N”???????????????,???????????????,??????,???????????????,??,????????????,??????????????????????,??,?????????????????????(?????)

??
???:????