摘要： 通过分析FD集中F的最小归并依赖集特征，提出了初等归并依赖集和最小归并依赖集，定义了初等最小归并依赖集的弱左部冲突和弱右部冲突、Pek(保持FD集，无损连接且满足初等关键词范式)等概念。讨论了数据库模式分解为初等关键词范式的无α环判定问题，实验证明，在初等归并依赖集D有弱左部或弱右部冲突时，满足Pek的分解具有α环，该分解算法是有效的。
关键词:
无内部冲突,
弱左部冲突,
弱右部冲突,
初等关键字范式
Abstract: By analyzing the minimum merge dependency set characteristics of F in FD set, the elementary merge dependency set and minimum merge dependency set are presented. Notions of weak left side conflict, weak right side conflict under elementary merge dependency set of F and Pek(join-lossless, FD and Elementary Key Normal Form(EKNF)) are introduced. The scheme decomposition is discussed and the result concludes that when the elementary merge dependency set of F has weak left side conflicts or weak right side conflict, the decomposition meeting Pek has α-cyclic. Experimental results show that the decomposition algorithm is effective.
Key words:
without inside conflict,
weak left side conflict,
weak right side conflict,
Elementary Key Normal Form(EKNF)
中图分类号:
赵龄强;郝忠孝;顾照鹏. FD无内部冲突时的Pek且无α环模式分解[J]. 计算机工程, 2008, 34(3): 81-82,9.
ZHAO Ling-qiang; HAO Zhong-xiao; GU Zhao-peng. Model Decomposition of Pek Without α-Cycle When Functional Dependency Without Inside Conflict[J]. Computer Engineering, 2008, 34(3): 81-82,9.