一个多时间粒度下时态模式的T3NF分解算法

对于时态数据库，时间维的引入使得如何有效地进行数据库设计以消除数据冗余和插入、删除异常显得尤为重要．可以通过支持多时间粒度的时态函数依赖（TFDs）约束对时态数模式进行规范化．但是多时间粒度的使用给数据库设计带来巨大的复杂性．一般来说，系统所能处理的和相当多的应用所涉及到的时态类型集满足全序关系．对于这种具有全序时态类型集的时态模式，通过分析TFD臬所具有的良好特性，给出了一个得到满足时态第三范式（T3NF）的无损分解的多项式时间的算法．

T3NF Decomposition Algorithm of Temporal Schemes with Multiple Granularities of Time

For temporal databases, because adoption of the temporal dimension, how to design effectively databases such that data redundancy and insertion, deletion anomalies can be eliminated is especially important. Therefore, temporal functional dependencies (TFDs) that support multiple time granularities may be used to normalize temporal schemes. But usages of multiple time granularities make it very complicated to design a database. Generally, the set of temporal types that can be processed by a system and involved in lots of applications, meet the totally ordered relation. For the temporal schemes with a totally ordered set of temporal types, by analyzing good properties of sets of TFDs, a polynomial algorithm that may obtain lossless decompositions satisfying the temporal third form (T3NF) is given.