On the desirability of omega-acyclic database schemes.
Nguyễn Văn Định · Journal of Computer Science and Cybernetics · 2012
In this paper we study a subclass of acyclic database schemes, the wacyclic database schemes and someclosely related problems.We first prove that with this class given here, the notion of acyclic hypergraphs used by graph theorists is equivalent to the notion, in the sense relevant to database theories.In the last of the paper, new characterizations for the class of the w-acyclic database schemes are also given.T6m tll.t.Trong bai bao nay, chung t6i nghien CUll m9t 16-p con cila cac hroc do CO' sO-dir lieu, d6 111, 16-p cac hro'cdo CSDL wphi chu irinh, Chung t6i da chtrng minh diro'c ding vo i lap nay thl khai niern phi chu trinh.cua cac sieu do thj diro'c djnh nghia trong 1:9' th uyet do thi va trong 1:9' th uyet CSDL 111, tucng diro'ng.Phat trie'n cac ket qua cda 1:9' thuydt do thj, chung t6i da du'a ra nhirng d~c trtrng m&icho 16-p cac hro'c do nay.