偏序时态模式下规范覆盖问题*

目前有效的多时间粒度时态数据库设计方法多针对全序时态模式，当时态模式的时态类型集为偏序集时，由于涉及时态类型间的最大下界等操作而使其难以实现。针对偏序时态模式的规范覆盖问题进行研究，提出了偏序TFD（时态函数依赖）集有限闭包、偏序模式属性集有限闭包、偏序无冗余覆盖和偏序规范TFD集等概念，解决了偏序TFD成员籍问题；并给出了偏序TFD集的规范覆盖算法，对其正确性进行了证明，对算法的时间复杂度进行了分析。为偏序时态模式的综合范式分解问题研究奠定基础。

Research on canonical cover in partial order temporal scheme

Existing effective design methods of temporal database with multiple time granularities are almost designed for totally-ordered temporal scheme,it can hardly be used for partial-ordered temporal scheme because of complex operations such as greatest lower bound applied to temporal types.This paper investigated canonical cover of partial-order temporal scheme,gave the concepts of partial-order TFD(temporal functional dependency) set limited closure,partial-order scheme attribute set limited closure,partial-or...