外部闭包及其在关系数据库中的应用

EXTERNAL CLOSURE AND ITS APPLICATION IN RELATIONAL DATABASE

本文引入了广义ＦＤ路和外部闭包的概念，将它们应用于函数依赖集的无冗余覆盖计算，有效地减少了计算的闭包个数．并在此基础上提出了一个新的３ＮＦ合成算法，将常用的３ＮＦ合成算法中的２次无冗余覆盖计算合并为１次，显著地减少了计算闭包总个数．

In this paper,the authors start with the introduction of generalized FD path and external closure.With the application of them,they show that the number of closures are reduced when calculating the nonredundant cover of a given functional dependency set.Then a new 3NF synthesis algorithm is presented.In this algorithm,the calculation of nonredundant cover in 3NF synthesis is reduced from two passes to one.So the total number of closures that to be calculated are significantly reduced.