中文摘要：

由于当前已有的在非确定数据库上的Tbp-k查询普遍基于元组层面,使得应用受限.为了让查询结果更符合直觉,提出了两种新的非确定数据库上的基于x-元组层面的Top-k查询及其执行算法.这两种新的查询综合x-元组中各元组的评分和置信度,获得在返回结果中最具实际意义的位置.查询的执行算法经过优化,执行效率明显改善.

英文摘要：

Since the pre-existing Top-fc queries in uncertain databases almost are based on tuple level rather than x-tuple level restricts its application.The paper proposes two new instance-level Top-fc queries and executive algorithm in uncertain databases in order to get intuitive query results.These two new queries take both rank and confidence of each x-tuple＇s tuple,figuring out the most meaningful position in the returned results.After the optimization of the executive algorithm,its executive efficiency has been improved significantly.