一个多时间粒度下时态函数依赖的有限属性闭包算法

为了有效地进行时态数据库设计，支持多时间粒度的时态函数依赖(TFDs)被用于时态模式的规范化．时态模式规范化所要解决的一个关键问题是求解时态函数依赖的有限属性闭包问题．由于多时间粒度的使用，使得有限属性闭包问题变得非常复杂．实际上，TFDs与传统的函数依赖(FDs)之间存在着密切的联系．通过分析这些联系和封闭时态类型集的特性，利用传统FDs的相关算法提出一个有效的求解有限属性闭包的算法．通过分析和与相关算法的实验比较，该算法更加有效．

An Algorithm for Computing the Finite Closure of Attributes for Temporal Functional Dependencies with Multiple Time Granularities

In order to design temporal databases effectively, temporal functional dependencies (TFDs) supporting for multiple granularities of time are used to normalize temporal schemes. A crucial problem that needs to be solved for normalization of temporal databases is to compute the finite closure of attributes for TFDs. Usages of multiple granularities of time make it very complex to compute the finite closure of attributes. In fact, TFDs are proper extensions of traditional functional dependencies (FDs). Thus, there exist close relationships between TFDs and traditional FDs. By analyzing the relationships and properties of close sets of temporal types, an algorithm for computing effectively the finite closure of attributes is proposed by using the corresponding algorithm for traditional FDs. According to the analysis and the comparison with related algorithms, the algorithm proposed is more effective than the other ones.