Assume there is an 1:N relationship between entity A and B,A is the parent and B is child. The two entities are: A={AID,F1}B={BID,F2} At the physical design level, these two entities are convert into: A={AID,Fl}B={BID,F2,AIDA={AID,F1}B={BID,F2}A={AID,F1,BID}B={BID,F2}A={AID,F1,BID}B={BID,F2,AID}