时态类型集的封闭集

好的数据库逻辑设计目标是消除数据冗余以及插入和删除异常。对于时态数据库，可以利用具有多时间粒度的时态函数依赖（TFDs）约束对时态数据库进行规范化。要进行有效的数据库设计，需要解决有限属性闭包和成员籍等一些有关TFD的问题。为了方便计算机对时态类型的处理和找到有效的解决TFD的相关问题的算法，该文提出了封闭时态类型集的概念，并且给出了一个求给定TFD集的封闭集的算法。

Close Set of Set of Temporal Types

The purpose of good database logical design is to eliminate data redundancy and insertion and deletion anomalies. For temporal databases, it may be normalized by using constraints of temporal functional dependencies (TFDs) with multiple time granularities. For designin efficiently databases,it is necessary to solve some problems relevant to TFD, e.g. finite closure of attributes and membership problems. For thatemporal teypes can be expediently processed by computers and efficient algorithms what to solve problems relevant to TFD can be found, in this paper, the concept of close set of temporal types is introduced, and an algorithm what to seek a close set for given set of temporal types is given.