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An efficient approach for continuous density queries

Frontiers of Computer Science 2012年第5期6卷 581-595页

作者： Jie WEN Xiaofeng MENG Xing HAO Jianliang XU School of Information Renmin University of ChinaBeijing 100872China Department of Computer Science Hong Kong Baptist UniversityHong KongChina

In location-based services, a density query re- turns the regions with high concentrations of moving objects （MOs）. The use of density queries can help users identify crowded regions so as to avoid congestion. Most of the exist- ing methods try very hard to improve the accuracy of query results, but ignore query efficiency. However, response time is also an important concern in query processing and may have an impact on user experience. In order to address this issue, we present a new definition of continuous density queries. Our approach for processing continuous density queries is based on the new notion of a safe interval, using which the states of both dense and sparse regions are dynamically main- tained. Two indexing structures are also used to index candi- date regions for accelerating query processing and improving the quality of results. The efficiency and accuracy of our approach are shown through an experimental comparison with snapshot density queries.

关键词： continuous density queries safe interval query efficiency

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Improved Self-Indexing Inverted Files for Full-Text Retrieval

Improved Self-Indexing Inverted Files for Full-Text Retrieva...

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第四届全国信息检索与内容安全学术会议

作者： Rongbo Zhu~1 Xiaozhu Liu~(2+) ~1 College of Compute Science,South-Central University for Nationalities,Wuhan 430074,China ~2 State Key Lab of Software Engineering,Wuhan University,Wuhan 430072,China

Self-index is a promising way to improve retrieval time-and-space efficiency by compression index *** on the self-indexing inverted files,an improved inverted file self-index called IFSI is proposed for full-text information *** includes two level indexes:the first level index which contains a subset of the documents that are likely to be returned as top results;and the second level index which includes the surplus *** can create a skipped index on each compressed posting list with very little or no storage overhead with efficient coding *** also supports efficient incremental updates with allocating free space efficiently at the tail of post lists based on statistics-based *** simulation results and comparison with other schemes prove that the proposed IFSI can not only greatly reduce decompress time by skipping over unnecessary portions of the list,but also simultaneously allow extremely fast query processing of both conjunctive Boolean queries and ranked queries.

关键词： Self-indexing Space efficiency query efficiency Full-text retrieval

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QBXS:一种基于查询的XML文档存储方法

QBXS:一种基于查询的XML文档存储方法

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第二十届全国数据库学术会议

作者：章悦高军王腾蛟杨冬青唐世渭北京大学计算机系数据库实验室

1.引言XML(eXtensible Markup Language)已经成为因特网上数据表示和数据交换的标准。随着XML数据的不断增加,如何有效地存储XML数据成为一个迫切需要解决的问题。目前,虽然已经提出了一

关键词： XML Storage query-based query efficiency

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