5Ashrafi M z,Taniar D,Smith K.A new approach of elimina-ting redundant association roles [A].Proceedings of the 15 International Conference on Database and Expert Systems Applications[C].200d: 465 -474.
6Ferrara A,Liberatore P,Schaeff M.The complexity of action re- dundancy[A].Proceedings of the 9 Conference on Ad-vances in Ar- tifical Intelligence L.2005:1-12.