时态数据库理论研究

一个好的时态数据库逻辑设计目标是消除数据冗余以及插入、删除和更新异常。因此,我们对时态初等函数依赖,时态初等关键字,时态初等主属性,时态简单关键字,时态简单主属性进行了定义,并研究了时态初等关键字范式和时态简单范式的分解问题,给出了相关分解算法。最后,基于TFD和TMVD混合集提出了时态第四范式(T4NF),并给出了时态模式的T4NF的无损分解算法,对算法的可终止性、正确性进行了证明,对时间复杂度进行了分析。

Theoretical Study on Temporal Database

The purpose of a good database logical design is to eliminate data redundancy and insertion,deletion and update anomalies.Temporal database is the same case.In this paper,the notions of temporal elementary functional dependency,temporal elementary key,temporal elementary main attribute,temporal simple key and temporal simple main attribute are introduced. Decomposition algorithms that give lossless,dependency-preserving,TEKNF decompositions and lossless,dependency-preserving,TSNF decompositions and the proof for its termination and correction are given.Finally,Temporal forth normal form with respect to TFDs and TMVDs is given,Decomposition algorithm which is terminal and correct is presented that give lossless T4NF decompositions.