偏序时态模式下规范覆盖问题

摘要

Existing effective design methods of temporal database with multiple time granularities are almost designed for total-ly-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-order non-redundant cover and partial-order canonical TFD set etc. Solved the membership problem of partial-order TFD. It also proposed the partial-order TFD set' s canonical cover algorithm. And gave the proof for its correction and the time complexity analysis. It sets the foundation for research of synthesis normal form decomposition in partial-order temporal scheme.%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.