【摘要】 基于Vague集理论,提出了一种扩展Vague关系数据模型.在此基础上,讨论了Vague关系数据库中的扩展聚集操作过程,定义了一组Vague值的扩展标量聚集操作符,即count,sum,avg,max和min.最后根据max和min操作的性质,对它们的性能进行了优化,并给出了相应的算法,将其时间复杂度从原来的O(nΠ)缩减至O(n2).更多还原

【Abstract】 Based on the theory of vague set,an extended vague relational data model is proposed.Then,the process of extended aggregate operation is discussed and a group of extended scalar aggregate operators for vague values are defined including count,sum,avg,max and min.According to the properties of max and min,the optimization algorithms for their preferences are developed to reduce their time complexity from O(n_Π) to O(n~2).更多还原