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Efficient Set-correlation Operator Inside Databases

Journal of Computer Science & Technology 2016年第4期31卷 683-701页

作者： Fei Gao Shao-Xu Song Lei Chen Jian-Min Wang Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing 100084 China school of Software Tsinghua University Beijing 100084 China Department of Computer Science and Engineering Hong Kong University of Science and Technology Hong Kong China

Large scale of short text records are now prevalent, such as news highlights, scientific paper citations, and posted messages in a discussion forum, and are often stored as set records in hidden-Web databases. Many interesting information retrieval tasks are correspondingly raised on the correlation query over these short text records, such as finding hot topics over news highlights and searching related scientific papers on a certain topic. However, current relational database management systems （RDBMS） do not directly provide support on set correlation query. Thus, in this paper, we address both the effectiveness and the efficiency issues of set correlation query over set records in databases. First, we present a framework of set correlation query inside databases. To the best of our knowledge, only the Pearson＇s correlation can be implemented to construct token correlations by using RDBMS facilities. Thereby, we propose a novel correlation coefficient to extend Pearson＇s correlation, and provide a pure-SQL implementation inside databases. We further propose optimal strategies to set up correlation filtering threshold, which can greatly reduce the query time. Our theoretical analysis proves that with a proper setting of filtering threshold, we can improve the query efficiency with a little effectiveness loss. Finally, we conduct extensive experiments to show the effectiveness and the efficiency of proposed correlation query and optimization strategies.

关键词： set record correlation query correlation measure

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Pseudo-Randomness of Certain Sequences of k Symbols with Length pq

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Journal of Computer Science & Technology 2011年第2期26卷 276-282页

作者：陈智雄杜小妮吴晨煌 Department of Mathematics Putian University State Key Lab.of ISN Xidian University College of Mathematics and Information Science Northwest Normal University

The theory of finite pseudo-random binary sequences was built by C. Mauduit and A. Sarkozy and later extended to sequences of k symbols （or k-ary sequences）. Certain constructions of pseudo-random sequences of k symbols were presented over finite fields in the literature. In this paper, two families of sequences of k symbols are constructed by using the integers modulo pq for distinct odd primes p and q. The upper bounds on the well-distribution measure and the correlation measure of the families sequences are presented in terms of certain character sums over modulo pq residue class rings. And low bounds on the linear complexity profile are also estimated.

关键词： stream ciphers pseudo-random sequences well-distribution measure correlation measure discrete logarithm modulo pq residue class rings character sums

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