FD无内部冲突时的Pek且无α环模式分解  

Model Decomposition of Pek Without α-Cycle When Functional Dependency Without Inside Conflict

作　　者：赵龄强[1] 郝忠孝[1,2] 顾照鹏[1] 

机构地区：[1]哈尔滨理工大学计算机科学与技术学院 [2]哈尔滨工业大学计算机科学与技术学院,哈尔滨150001

出　　处：《计算机工程》2008年第3期81-82,90,共3页Computer Engineering

基　　金：黑龙江省自然科学基金资助项目(F00-06)

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。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 fight 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,

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 

分 类 号：TP311.13[自动化与计算机技术—计算机软件与理论]