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Adaptive load shedding for data stream using PI feedback controller

Journal of Computational Information Systems 2007年第5期3卷 1827-1832页

作者： Huang, Chongzheng Cai, Shaojiang Xie, Zhijun Zhang, Yuanyu Chen, Hong School of Information Renmin University of China Beijing 100872 China Key Laboratory of Data Engineering and Knowledge Engineering China School of Electronics and Information Engineering Xi'an Jiaotong University Xi'an 710000 China

Load shedding has been widely used in data stream management systems (DSMSs) to keep DSMSs running steadily. One key problem in load shedding is determining how much system load to shed. Existing works tend to adapt coarse algorithm (CA) to solve this problem. In this paper, we present an adaptive PI controller-based load shedding framework for data stream. The main contribution of this paper is our use of feedback control theory to design the load shedding scheme. In contrast to the existing approaches, we firstly apply system identification to establish a dynamic model to describe DSMS, which enables us analyze DSMS quantitatively. Then, based on the model, we use the Root Locus method to design the PI controller with proven performance guarantees. The adaptive framework has been implemented by modifying Borealis system. Theoretic analysis and experimental results demonstrate that our approach is robust even when system load changes frequently. Comparing to existing strategies, our approach also achieves significantly better performance.

关键词： Feedback control

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Minimizing XML Queries Using a Family of Constraints

Minimizing XML Queries Using a Family of Constraints

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International Conference on Fuzzy Systems and knowledge Discovery (FSKD)

作者： Xiping Liu Changxuan Wan School of Information Technology Jiangxi Key Laboratory of Data and Knowledge Engineering Jiangxi University of Finance and Economics Nanchang China

An effective way to optimize XML queries is to minimize XML queries. In this paper, we improve redundance elimination in XPath queries greatly by incorporating two novel kinds of constraints: parent constraint and sibling constraint, and by extending the tractable fragment to include descendant-or-self axis. The two novel kinds of constraints, together with child constraint and descendant constraint, form a family of constraints, which complicate the problem but offer possibilities for further minimization. Two techniques, tree augmentation and simulation augmentation, are employed to cope with constraints. We elaborate on the minimizing algorithms and running efficiencies both in the absence and in the presence of various kinds of constraints.

关键词： XML Polynomials Minimization methods Information technology Finance laboratories knowledge engineering Constraint optimization Fuzzy systems System testing

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The Rewriting Algorithm for Disjunctive Queries between Peer Ontologies

The Rewriting Algorithm for Disjunctive Queries between Peer...

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2007年第三届语义和知识网格国际会议(Third International Conference on Semantics,knowledge,and Grid)(SKG 2007)

作者： Biao Qin Shan Wang Dept. of Computer Science Renmin University of China Beijing 100872 China Key Laboratory of Data Engineering and Knowledge Engineering Ministry of EducationBeijing 100872 China

We study the problem of answering queries given a set of mappings between peer ontologies. In addition to the schema mapping between peer ontologies, there are axioms to give constraints to classes and properties. We propose a set of rules to build graphs for the axioms. Because the axioms have different properties, the generated graphs are classified into four sets. In each peer, its RDF/OWL query languages can support regular expressions. If it wants to be transitive along semantic paths in peer knowledge management systems, we must rewrite conjunctive and disjunctive queries between peers. Because conjunctive queries are well-understood, we focus on a novel algorithm to rewrite disjunctive queries along semantic paths based on the graphs. For all atoms of a disjunctive query, we consider its union as a set and find the maximum rewritings over peers through a graphical way. Finally we do extensive simulation experiments. The simulation results show our algorithm can generate more rewritings than the naive rewriting algorithm at each distance.

关键词： Ontologies Resource description framework OWL Terminology database languages Connectors knowledge management Extraterrestrial measurements Computer science laboratories

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Measuring Semantic Associaiton in Domain Ontology

Measuring Semantic Associaiton in Domain Ontology

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International Conference on Semantics, knowledge and Grid (SKG)

作者： Xuan Tian Haihua Li Xiaoyong Du School of Information Renmin University of China Beijing China Key Laboratory of Data Engineering and Knowledge Engineering MOESchool of Information Renmin University of China Beijing China

In domain ontology, semantic association (SA) is used to depict the correlation between two concepts. In this paper, we define semantic association degree (SAD) for measuring SA in the domain ontology. We first present a method to measure SAD of two direct related concepts by evaluating the semantic relationship between them, and then give another method to measure SAD of two indirect related concepts though SAD of two directed neighboring concepts. A set of comparison experiments show the benefit of our approaches.

关键词： Ontologies Psychology data mining Diseases Information retrieval laboratories data engineering knowledge engineering Text categorization History

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Finding Top-k Min-Cost Connected Trees in databases

Finding Top-k Min-Cost Connected Trees in Databases

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International Conference on data engineering

作者： Bolin Ding Jeffrey Xu Yu Shan Wang Lu Qin Xiao Zhang Xuemin Lin Chinese University of Hong Kong China Key Laboratory of Data Engineering and Knowledge Engineering MOE of China Renmin University of China China University of New South Wales Australia

ISBN: (纸本)1424408024

It is widely realized that the integration of database and information retrieval techniques will provide users with a wide range of high quality services. In this paper, we study processing an l-keyword query, p 1 , p 1 , ..., p l , against a relational database which can be modeled as a weighted graph, G(V, E). Here V is a set of nodes (tuples) and E is a set of edges representing foreign key references between tuples. Let V i ⊆ V be a set of nodes that contain the keyword p i . We study finding top-k minimum cost connected trees that contain at least one node in every subset V i , and denote our problem as GST-k When k = 1, it is known as a minimum cost group Steiner tree problem which is NP-complete. We observe that the number of keywords, l, is small, and propose a novel parameterized solution, with l as a parameter, to find the optimal GST-1, in time complexity O(3 l n + 2 l ((l + logn)n + m)), where n and m are the numbers of nodes and edges in graph G. Our solution can handle graphs with a large number of nodes. Our GST-1 solution can be easily extended to support GST-k, which outperforms the existing GST-k solutions over both weighted undirected/directed graphs. We conducted extensive experimental studies, and report our finding.

关键词： Tree graphs Relational databases Costs laboratories data engineering knowledge engineering Australia Information retrieval

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Milling of multi-relational association rules

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Ruan Jian Xue Bao/Journal of Software 2007年第11期18卷 2752-2765页

作者： He, Jun Liu, Hong-Yan Du, Xiao-Yong Department of Computer Science and Technology Renmin University of China Beijing 100872 China Department of Management Science and Engineering Tsinghua University Beijing 100084 China Key Laboratory of Data Engineering and Knowledge Engineering Beijing 100872 China

Association rule mining is one of the most important and basic technique in data mining, which has been studied extensively and has a wide range of applications. However, as traditional data mining algorithms usually only focus on analyzing data organized in single table, applying these algorithms in multi-relational data environment will result in many problems. This paper summarizes these problems, proposes a framework for the mining of multi-relational association rule, and gives a definition of the mining task. After classifying the existing work into two categories, it describes the main techniques used in several typical algorithms, and it also makes comparison and analysis among them. Finally, it points out some issues unsolved and some future further research work in this area.

关键词： data mining

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Preface

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计算机科学技术学报（英文版） 2007年第2期22卷插1-插2页

作者： Shan Wang Jian-Zhong Li Scholl of Information Key Lab Data Engineering and Knowledge EngineeringRenmin University of China Department of Computer Science and Technology Harbin Institute of Technology

Recent advances in database related applications propose many new challenges and have inspired database researchers and practitioners to further make their efforts on new database technologies.

关键词：

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database Research： Achievements and Challenges

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Journal of Computer Science & Technology 2006年第5期21卷 823-837页

作者：王珊杜小勇孟小峰陈红 School of Information Renmin University of China MOE Key Lab of Data Engineering and Knowledge Engineering Beijing 100872 P.R. China

database system is the infrastructure of the modern information system. The R＆D in the database system and its technologies is one of the important research topics in the field. The database R＆D in China took off later but it moves along by giant steps. This report presents the achievements Renmin University of China （RUC） has made in the past 25 years and at the same time addresses some of the research projects we, RUC, are currently working on. The National Natural Science Foundation of China supports and initiates most of our research projects and these successfully conducted projects have produced fruitful results.

关键词： database management system parallel database systems Chinese database systems self-managing databases P2P computing and databases data warehousing OLAP Web data management XML mobile data management semantic web contextual information retrieval

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2DCMA： An Effective Maintenance Algorithm of Materialized Views in Peer data Management Systems

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Journal of Computer Science & Technology 2006年第4期21卷 503-512页

作者：覃飙王珊杜小勇 School of Information Renmin University of China Beijing 100872 P.R. China Key Laboratory of Data Engineering and Knowledge Engineering Ministry of Education Beijing 100872 P.R. China

Update management is very important for data integration systems. So update management in peer data management systems （PDMSs） is a hot research area. This paper researches on view maintenance in PDMSs. First, the definition of view is extended and the peer view, local view and global view are proposed according to the requirements of applications. There are two main factors to influence materialized views in PDMSs. One is that schema mappings between peers are changed, and the other is that peers update their data. Based on the requirements, this paper proposes an algorithm called 2DCMA, which includes two sub-algorithms： data and definition consistency maintenance algorithm% to effectively maintain views. For data consistency maintenance, Mork＇s rules are extended for governing the use of updategrams and boosters. The new rule system can be used to optimize the execution plan. And are extended for the data consistency maintenance algorithm is based on the new rule system. Furthermore, an ECA rule is adopted for definition consistency maintenance. Finally, extensive simulation experiments are conducted in SPDMS. The simulation results show that the 2DCMA algorithm has better performance than that of Mork＇s when maintaining data consistency. And the 2DCMA algorithm has better performance than that of centralized view maintenance algorithm when maintaining definition consistency.

关键词： view maintenance peer data management system schema mapping ECA rule

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Maintaining materialized relations incrementally to improve performance of ontology query

Maintaining materialized relations incrementally to improve ...

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7th International Conference on Web-Age Information Management Workshops, WAIM 2006

作者： Li, Man Du, Xiaoyong Wang, Shan School of Information Renmin University of China China Key Laboratory of Data Engineering and Knowledge Engineering MOE 100872 Beijing China

ISBN: (纸本)0769527051

For ontology-based applications, the efficiency of ontology query is vital. Different from existing approaches, the paper improves performance of ontology query by materializing some derived relations. Experimental results show that the integrated performance of ontology query can be improved greatly by maintaining materialized relations and the materialized relations technique has good scalability. Here the challenge is how to maintain the materialized relations incrementally with the update of ontologies. Because transitive relations are in common use in ontology, the paper proposes a novel algorithm for maintaining transitive materialized relations incrementally based on a special weighted materialized relation transitive graph, which can solve the coexistence problem of multiple derived paths better and proves the correctness of the algorithm. © 2006 IEEE.

关键词： Ontology

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