设计关系数据库模式的优化综合算法

AN IMPROVED SYNTHESIS ALGORITHM OF DESIGNING RELATIONAL DATABASE SCHEME

本文叙述了一个设计关系数据库模式的优化综合算法。它根据给定的一关系数据库的一组函数依赖,并基于求子集闭包理论、函数依赖的哈密顿环(Hamil-tonian Cycle)及关系数据库理论,产生一个属于“基本关键字范式”-EKNF(Ele-mentary Key Normal Form)的关系数据库模式。所产生的EKNF较大限度地删除了多余属性,消除函数依赖的冗余度,而获得一组好的RL—minimum FD。并且算法的时间复杂度是多项式的,从而此算法具有很重要的实用价值。

An improved algorithm of designing relational database scheme is described in this paper. From a given set of FD's (Functional Dependencies) this algorithm can find a relational database scheme in EKNF(Elementary Key Normal Form)based on theory of subset closures, relational database and FD' s Hamiltonian cycles. This algorithm eliminates not only extraneous attributes and other redundancies, but also superfluities from a given set of functional dependencies. Following this algorithm, a better LR - minimum FD is obtained, and the time complexity of the algorithm is polynomial. So, this algorithm is more practical and efficient in designing a relational database scheme.