条件函数依赖的增量计算

条件函数依赖是对传统函数依赖的扩展,它通过引入条件模式,使其语义比函数依赖更精确、表达能力更强。然而,条件函数依赖的计算需要消耗较多的时间,为了提高条件函数依赖挖掘的效率,研究了条件函数依赖增量维护方法。针对数据集增加、删除、修改3种情况分别分析了条件函数依赖集变化规律,提出了条件函数依赖的增量计算算法,从而能够在数据库变化情况下,高效、动态地维护条件函数依赖。同时,在理论上对算法中关键步骤的正确性进行了论证,并通过实验验证了算法的有效性。

Incremental calculation of conditional functional dependencies

A conditional functional dependency (CFD) is an extension of the traditional functional dependency (FD). By introducing the conditional pattern, the CFD is more accurate and more expressive than FDs in semantics. However, it is time-consuming for computing CFDs. In order to improve the efficiency of CFDs, the incremental maintenance method for CFDs is studied. The changing rules on the conditions of three different situations (i.e., dataset insertion, deletion, update) are analyzed, and an incremental algorithm for calculating CFDs is proposed, so that we can efficiently and dynamically maintain CFDs while the database is changing. At the same time, the correctness of key steps of the algorithm is demonstrated, and the validness of the algorithm is verified through the experiments.