具有多时间粒度的时态数据库初等关键字、简单范式分解问题研究

一个好的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．对于时态数据库也是如此．提出了时态初等函数依赖、时态初等关键字、时态简单关键字等概念，在此基础上利用具有多时间粒度的时态函数依赖（TFD）约束对时态数据库进行了规范化研究，提出了规范程度高于时态三范式低于时态Boyce—Code范式的时态初等关键字范式（TEKNF）及时态简单范式（TSNF），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，并对算法的可终止性、正确性进行了证明，对时间复杂度进行了分析．

Research on Decomposition Problem of Temporal Elementary Key Normal form and Temporal Simple Normal Form in Temporal Database with Multiple Time Granularities

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 simple key are introduced. On this basis, the normalization of temporal database is studied by using constraints of temporal functional dependency(TFD) with multiple time granularities; the concept of temporal elementary key normal form(TEKNF) and temporal simple normal form(TSNF) is introduced; the proof that the normalization degree of both normal form is between T3NF and TBCNF and the normalization degree of TEKNF is lower than that of TSNF is given. Decomposition algorithms that give lossless, dependency preserving, TEKNF decompositions and lossless, dependency preserving, TSNF decompositions and the proof for its termination and correction are also given.