全序时态模式中时态函数依赖的覆盖问题研究

Study on covering problem of temporal functional dependencies intotally-ordered temporal scheme

与传统的关系数据库中的函数依赖一样,时态数据库中全序时态模块模式下的时态函数依赖也存在着冗余问题,因而有效地消除冗余的时态函数依赖是全序时态函数依赖集化简的基础。在全序时态模式下提出全序无冗余覆盖、全序规范覆盖和全序最小覆盖等概念,同时给出了全序无冗余覆盖、全序规范覆盖集和全序最小覆盖集的算法及相关定理,并给出了其正确性证明,对其时间复杂度进行了分析。

As in the traditional relational database, there also exists redundant problem of functional dependencies in temporal database with totally-ordered temporal scheme. Effective elimination of redundant temporal functional dependencies （TFDs） is the foundation of simplification of totally-ordered TFDs set. This paper put forwards the concepts of totally-ordered no-redundant covering, totally-ordered canonical covering, totally-ordered minimal covering and so on, and also presented the relevant theorems and algorithms for them. Also gave the proof for the algorithms＇ correction, termination and the time complexity analysis.