To solve the query processing correctness problem for semantic-based relational data integration,the semantics of SAPRQL（simple protocol and RDF query language） queries is defined.In the course of query rewriting,al...To solve the query processing correctness problem for semantic-based relational data integration,the semantics of SAPRQL（simple protocol and RDF query language） queries is defined.In the course of query rewriting,all relative tables are found and decomposed into minimal connectable units.Minimal connectable units are joined according to semantic queries to produce the semantically correct query plans.Algorithms for query rewriting and transforming are presented.Computational complexity of the algorithms is discussed.Under the worst case,the query decomposing algorithm can be finished in O（n2） time and the query rewriting algorithm requires O（nm） time.And the performance of the algorithms is verified by experiments,and experimental results show that when the length of query is less than 8,the query processing algorithms can provide satisfactory performance.展开更多
A defining characteristic of continuous queries over on-line data streams,possibly bounded by sliding windows,is the potentially infinite and time-evolving nature of their inputs and outputs.For different update patte...A defining characteristic of continuous queries over on-line data streams,possibly bounded by sliding windows,is the potentially infinite and time-evolving nature of their inputs and outputs.For different update patterns of continuous queries,suitable data structures bring great query processing efficiency.In this paper,we proposed a data structure suitable for weak nonmonotonic update pattern in which the lifetime of each tuple is known at generation time,but the length of lifetime is not necessarily the same.The new data structure combined the ladder queue with the feature of weak non-monotonic update pattern.The experiment results show that the new data structure performs much better than the traditional calendar queue in many cases.展开更多
As one of the commonly used queries in modern databases, skyline query has received extensive attention from database research community. The uncertainty of the data in wireless sensor networks makes the corresponding...As one of the commonly used queries in modern databases, skyline query has received extensive attention from database research community. The uncertainty of the data in wireless sensor networks makes the corresponding skyline uncertain and not unique. This paper investigates the Pr-Skyline problem, i.e., how to compute the skyline with the highest existence probability in a computational and energy-efficient way. We formulate the problem and prove that it is NP-Complete and cannot be approximated in a given expression. However, the proposed algorithm SKY-SEARCH with pruning techniques can guarantee the computational efficiency given relatively large input size, while the filter-based distributed optimization strategy significantly reduces the transmission cost and the required storage space of the sensor nodes. Extensive experiments verify the efficiency and scalability of SKY-SEARCH and the distributed optimizing strategy.展开更多
Recently, new techniques to efficiently manage current and past location information of moving objects have received significant interests in the area of moving object databases and location based service systems. In ...Recently, new techniques to efficiently manage current and past location information of moving objects have received significant interests in the area of moving object databases and location based service systems. In this paper, we exploit query processing schemes for location management systems, which consist of multiple data processing nodes to handle massive volume of moving objects such as cellular phone users. To show the usefulness of the proposed schemes, some experimental results showing performance factors regarding distributed query processing are explained. In our experiments, we use two kinds of data set: one is generated by the extended GSTD simulator and another is generated by the real time data generator which generates location sensing reports of various types of users having different movement patterns.展开更多
Modern search systems have become a fundamental tool for accessing the massive amount of information stored in different repositories.These systems use sophisticated techniques to efficiently process a high volume of ...Modern search systems have become a fundamental tool for accessing the massive amount of information stored in different repositories.These systems use sophisticated techniques to efficiently process a high volume of queries(thus optimizing energy consumption).One of these techniques is caching,which is implemented at different levels of a search architecture.In this work,we propose a novel caching strategy that speeds up dynamic pruning techniques(such as Maxscore)by exploiting the information of the lowest(Min)and highest(Max)document identifiers that appear as the result of a previously submitted query.We name this technique as Min/Max caching.The idea is to use Min/Max information for pruning the terms’posting lists in the query before executing the ranking algorithm in a document-at-a-time(DAAT)approach.The proposed technique uses low memory resources,returns safe results,and complements other levels of caching(if present).We also combine the approach with different access policies.Extensive experimentation on real-world data shows that the proposed method increases query processing speedup up to 1.23x and can also reduce high-percentile tail latency(up to 2.0x speedup),an essential requirement for operational scenarios.We evaluate different access and eviction cache policies based on different decision criteria.Our findings confirm that considering the cost of the cached items(cost-aware policies)allows more computation savings.展开更多
An extent join to compute path expressions containing parent-children andancestor-descendent operations and two path expression optimization rules, path-shortening andpath-complementing, are presented in this paper. P...An extent join to compute path expressions containing parent-children andancestor-descendent operations and two path expression optimization rules, path-shortening andpath-complementing, are presented in this paper. Path-shortening reduces the number of joins byshortening the path while path-complementing optimizes the path execution by using an equivalentcomplementary path expression to compute the original one. Experimental results show that thealgorithms proposed are more efficient than traditional algorithms.展开更多
Recent development of wireless communication technologies and the popularity of smart phones .are making location-based services （LBS） popular. However, requesting queries to LBS servers with users＇ exact locations...Recent development of wireless communication technologies and the popularity of smart phones .are making location-based services （LBS） popular. However, requesting queries to LBS servers with users＇ exact locations may threat the privacy of users. Therefore, there have been many researches on generating a cloaked query region for user privacy protection. Consequently, an efficient query processing algorithm for a query region is required. So, in this paper, we propose k-nearest neighbor query （k-NN） processing algorithms for a query region in road networks. To efficiently retrieve k-NN points of interest （POIs）, we make use of the Island index. We also propose a method that generates an adaptive Island index to improve the query processing performance and storage usage. Finally, we show by our performance analysis that our k-NN query processing algorithms outperform the existing k-Range Nearest Neighbor （kRNN） algorithm in terms of network expansion cost and query processing time.展开更多
In this paper, constrained K closest pairs query is introduced, wbich retrieves the K closest pairs satisfying the given spatial constraint from two datasets. For data sets indexed by R trees in spatial databases, thr...In this paper, constrained K closest pairs query is introduced, wbich retrieves the K closest pairs satisfying the given spatial constraint from two datasets. For data sets indexed by R trees in spatial databases, three algorithms are presented for answering this kind of query. Among of them, two-phase Range＋Join and Join＋Range algorithms adopt the strategy that changes the execution order of range and closest pairs queries, and constrained heap-based algorithm utilizes extended distance functions to prune search space and minimize the pruning distance. Experimental results show that constrained heap-base algorithm has better applicability and performance than two-phase algorithms.展开更多
Recently,in the area of big data,some popular applications such as web search engines and recommendation systems,face the problem to diversify results during query processing.In this sense,it is both significant and e...Recently,in the area of big data,some popular applications such as web search engines and recommendation systems,face the problem to diversify results during query processing.In this sense,it is both significant and essential to propose methods to deal with big data in order to increase the diversity of the result set.In this paper,we firstly define the diversity of a set and the ability of an element to improve the overall diversity.Based on these definitions,we propose a diversification framework which has good performance in terms of effectiveness and efficiency.Also,this framework has theoretical guarantee on probability of success.Secondly,we design implementation algorithms based on this framework for both numerical and string data.Thirdly,for numerical and string data respectively,we carry out extensive experiments on real data to verify the performance of our proposed framework,and also perform scalability experiments on synthetic data.展开更多
Area query processing is significant for various applications of wireless sensor networks since it can request information of particular areas in the monitored environment. Existing query processing techniques cannot ...Area query processing is significant for various applications of wireless sensor networks since it can request information of particular areas in the monitored environment. Existing query processing techniques cannot solve area queries. Intuitively, centralized processing on Base Station can accomplish area queries via collecting information from all sensor nodes. However, this method is not suitable for wireless sensor networks with limited energy since a large amount of energy is wasted for reporting useless data. This motivates us to propose an energy-efficient in-network area query processing scheme. In our scheme, the monitored area is partitioned into grids, and a unique gray code number is used to represent a Grid ID （GID）, which is also an effective way to describe an area. Furthermore, a reporting tree is constructed to process area merging and data aggregations. Based on the properties of GIDs, subareas can be merged easily and useless data can be discarded as early as possible to reduce energy consumption. For energy-efficiently answering continuous queries, we also design an incremental update method to continuously generate query results. In essence, all of these strategies are pivots to conserve energy consumption. With a thorough simulation study, it is shown that our scheme is effective and energy-efficient展开更多
Cloud computing is a very promising paradigm of service-oriented computing. One major benefit of cloud computing is its elasticity, i.e., the system＇s capacity to provide and remove resources automatically at runtime...Cloud computing is a very promising paradigm of service-oriented computing. One major benefit of cloud computing is its elasticity, i.e., the system＇s capacity to provide and remove resources automatically at runtime. For that, it is essential to design and implement an efficient and effective technique that takes full advantage of the system＇s potential flexibility. This paper presents a non-intrusive approach that monitors the performance of relational database management systems in a cloud infrastructure, and automatically makes decisions to maximize the efficiency of the provider＇s environment while still satisfying agreed upon ＂service level agreements＂ （SLAs）. Our experiments conducted on Amazon＇s cloud infrastructure, confirm that our technique is capable of automatically and dynamically adjusting the system＇s allocated resources observing the SLA.展开更多
In recent years there has been a significant interest in peer-to-peer （P2P） environments in the community of data management. However, almost all work, so far, is focused on exact query processing in current P2P dat...In recent years there has been a significant interest in peer-to-peer （P2P） environments in the community of data management. However, almost all work, so far, is focused on exact query processing in current P2P data systems. The autonomy of peers also is not considered enough. In addition, the system cost is very high because the information publishing method of shared data is based on each document instead of document set. In this paper, abstract indices （AbIx） are presented to implement content-based approximate queries in centralized, distributed and structured P2P data systems. It can be used to search as few peers as possible but get as many returns satisfying users＇ queries as possible on the guarantee of high autonomy of peers. Also, abstract indices have low system cost, can improve the query processing speed, and support very frequent updates and the set information publishing method. In order to verify the effectiveness of abstract indices, a simulator of 10,000 peers, over 3 million documents is made, and several metrics are proposed. The experimental results show that abstract indices work well in various P2P data systems.展开更多
Multiple time series （MTS）, which describes an object in multi-dimensions, is based on single time series and has been proved to be useful. In this paper, a new analytical method called α/β-Dominant-Skyline on MTS...Multiple time series （MTS）, which describes an object in multi-dimensions, is based on single time series and has been proved to be useful. In this paper, a new analytical method called α/β-Dominant-Skyline on MTS and a formal definition of the α/β-dominant skyline MTS are given. Also, three algorithms, called NL, BC and MFB, are proposed to address the α/β-dominant skyline queries over MTS. Finally experimental results on both synthetic and real data verify the correctness and effectiveness of the proposed method and algorithms.展开更多
Purpose-Resilient distributed processing technique(RDPT),in which mapper and reducer are simplified with the Spark contexts and support distributed parallel query processing.Design/methodology/approach-The proposed wo...Purpose-Resilient distributed processing technique(RDPT),in which mapper and reducer are simplified with the Spark contexts and support distributed parallel query processing.Design/methodology/approach-The proposed work is implemented with Pig Latin with Spark contexts to develop query processing in a distributed environment.Findings-Query processing in Hadoop influences the distributed processing with the MapReduce model.MapReduce caters to the works on different nodes with the implementation of complex mappers and reducers.Its results are valid for some extent size of the data.Originality/value-Pig supports the required parallel processing framework with the following constructs during the processing of queries:FOREACH;FLATTEN;COGROUP.展开更多
In order to reduce the disk access time, a database can be stored on several simultaneously accessi- ble disks. In this paper, we are concerned with the dynamic d-attribute database allocation problem for range querie...In order to reduce the disk access time, a database can be stored on several simultaneously accessi- ble disks. In this paper, we are concerned with the dynamic d-attribute database allocation problem for range queries. An allocation method, called coordinate modulo allocation method, is proposed to al- locate data in a d-attribute database among disks so that the maximum disk accessing concurrency can be achieved for range queries. Our analysis and experiments show that the method achieves the optimum or near-optimum parallelism for range queries. The paper offers the conditions under which the method is optimal. The worst case bounds of the performance of the method are also given. In addi- tion, the parallel algorithm of processing range queries is described at the end of the paper. The meth- od has been used in the statistic and scientific database management system which is being designed by us.展开更多
The idea of positional inverted index is exploited for indexing of graph database. The main idea is the use of hashing tables in order to prune a considerable portion of graph database that cannot contain the answer s...The idea of positional inverted index is exploited for indexing of graph database. The main idea is the use of hashing tables in order to prune a considerable portion of graph database that cannot contain the answer set. These tables are implemented using column-based techniques and are used to store graphs of database, frequent sub-graphs and the neighborhood of nodes. In order to exact checking of remaining graphs, the vertex invariant is used for isomorphism test which can be parallel implemented. The results of evaluation indicate that proposed method outperforms existing methods.展开更多
In hybrid wireless sensor networks,sensor mobility causes the query areas to change dynamically.Aiming at the problem of inefficiency in processing the data aggregation queries in dynamic query areas,this paper propos...In hybrid wireless sensor networks,sensor mobility causes the query areas to change dynamically.Aiming at the problem of inefficiency in processing the data aggregation queries in dynamic query areas,this paper proposes a processing approach for event-based location aware queries(ELAQ),which includes query dissemination algorithm,maximum distance projection proxy selection algorithm,in-network query propagation,and aggregation algorithm.ELAQs are triggered by the events and the query results are dependent on mobile sensors'location,which are the characteristics of ELAQ model.The results show that compared with the TinyDB query processing approach,ELAQ processing approach increases the accuracy of the query result and decreases the query response time.展开更多
基金Weaponry Equipment Pre-Research Foundation of PLA Equipment Ministry (No. 9140A06050409JB8102)Pre-Research Foundation of PLA University of Science and Technology (No. 2009JSJ11)
文摘To solve the query processing correctness problem for semantic-based relational data integration,the semantics of SAPRQL（simple protocol and RDF query language） queries is defined.In the course of query rewriting,all relative tables are found and decomposed into minimal connectable units.Minimal connectable units are joined according to semantic queries to produce the semantically correct query plans.Algorithms for query rewriting and transforming are presented.Computational complexity of the algorithms is discussed.Under the worst case,the query decomposing algorithm can be finished in O（n2） time and the query rewriting algorithm requires O（nm） time.And the performance of the algorithms is verified by experiments,and experimental results show that when the length of query is less than 8,the query processing algorithms can provide satisfactory performance.
基金Funded by the Natural Science Foundation of China (No. 60873030)National High Technology Research and Development Program of China (No. 2007AA01Z309)Defense Pre-Research Foundation of China (No. 9140A04010209JW0504 and No. 9140A15040208JW0501)
文摘A defining characteristic of continuous queries over on-line data streams,possibly bounded by sliding windows,is the potentially infinite and time-evolving nature of their inputs and outputs.For different update patterns of continuous queries,suitable data structures bring great query processing efficiency.In this paper,we proposed a data structure suitable for weak nonmonotonic update pattern in which the lifetime of each tuple is known at generation time,but the length of lifetime is not necessarily the same.The new data structure combined the ladder queue with the feature of weak non-monotonic update pattern.The experiment results show that the new data structure performs much better than the traditional calendar queue in many cases.
文摘As one of the commonly used queries in modern databases, skyline query has received extensive attention from database research community. The uncertainty of the data in wireless sensor networks makes the corresponding skyline uncertain and not unique. This paper investigates the Pr-Skyline problem, i.e., how to compute the skyline with the highest existence probability in a computational and energy-efficient way. We formulate the problem and prove that it is NP-Complete and cannot be approximated in a given expression. However, the proposed algorithm SKY-SEARCH with pruning techniques can guarantee the computational efficiency given relatively large input size, while the filter-based distributed optimization strategy significantly reduces the transmission cost and the required storage space of the sensor nodes. Extensive experiments verify the efficiency and scalability of SKY-SEARCH and the distributed optimizing strategy.
基金This work is supported by the Ministry of Inform ation & Comm unicationsKoreaunder theInformation Technology Research Center(ITRC) Support Program.
文摘Recently, new techniques to efficiently manage current and past location information of moving objects have received significant interests in the area of moving object databases and location based service systems. In this paper, we exploit query processing schemes for location management systems, which consist of multiple data processing nodes to handle massive volume of moving objects such as cellular phone users. To show the usefulness of the proposed schemes, some experimental results showing performance factors regarding distributed query processing are explained. In our experiments, we use two kinds of data set: one is generated by the extended GSTD simulator and another is generated by the real time data generator which generates location sensing reports of various types of users having different movement patterns.
基金funded by the Universidad Nacional de Luján(Argentina)Disp.CDCB:28421.
文摘Modern search systems have become a fundamental tool for accessing the massive amount of information stored in different repositories.These systems use sophisticated techniques to efficiently process a high volume of queries(thus optimizing energy consumption).One of these techniques is caching,which is implemented at different levels of a search architecture.In this work,we propose a novel caching strategy that speeds up dynamic pruning techniques(such as Maxscore)by exploiting the information of the lowest(Min)and highest(Max)document identifiers that appear as the result of a previously submitted query.We name this technique as Min/Max caching.The idea is to use Min/Max information for pruning the terms’posting lists in the query before executing the ranking algorithm in a document-at-a-time(DAAT)approach.The proposed technique uses low memory resources,returns safe results,and complements other levels of caching(if present).We also combine the approach with different access policies.Extensive experimentation on real-world data shows that the proposed method increases query processing speedup up to 1.23x and can also reduce high-percentile tail latency(up to 2.0x speedup),an essential requirement for operational scenarios.We evaluate different access and eviction cache policies based on different decision criteria.Our findings confirm that considering the cost of the cached items(cost-aware policies)allows more computation savings.
文摘An extent join to compute path expressions containing parent-children andancestor-descendent operations and two path expression optimization rules, path-shortening andpath-complementing, are presented in this paper. Path-shortening reduces the number of joins byshortening the path while path-complementing optimizes the path execution by using an equivalentcomplementary path expression to compute the original one. Experimental results show that thealgorithms proposed are more efficient than traditional algorithms.
基金supported by the Korea Institute of Science and Technology Information (KISTI)
文摘Recent development of wireless communication technologies and the popularity of smart phones .are making location-based services （LBS） popular. However, requesting queries to LBS servers with users＇ exact locations may threat the privacy of users. Therefore, there have been many researches on generating a cloaked query region for user privacy protection. Consequently, an efficient query processing algorithm for a query region is required. So, in this paper, we propose k-nearest neighbor query （k-NN） processing algorithms for a query region in road networks. To efficiently retrieve k-NN points of interest （POIs）, we make use of the Island index. We also propose a method that generates an adaptive Island index to improve the query processing performance and storage usage. Finally, we show by our performance analysis that our k-NN query processing algorithms outperform the existing k-Range Nearest Neighbor （kRNN） algorithm in terms of network expansion cost and query processing time.
基金Supported by National Natural Science Foundationof China (60073045)
文摘In this paper, constrained K closest pairs query is introduced, wbich retrieves the K closest pairs satisfying the given spatial constraint from two datasets. For data sets indexed by R trees in spatial databases, three algorithms are presented for answering this kind of query. Among of them, two-phase Range＋Join and Join＋Range algorithms adopt the strategy that changes the execution order of range and closest pairs queries, and constrained heap-based algorithm utilizes extended distance functions to prune search space and minimize the pruning distance. Experimental results show that constrained heap-base algorithm has better applicability and performance than two-phase algorithms.
基金This paper was partially supported by NSFC(Grant Nos.U1509216,U1866602,61602129)and Microsoft Research Asia.
文摘Recently,in the area of big data,some popular applications such as web search engines and recommendation systems,face the problem to diversify results during query processing.In this sense,it is both significant and essential to propose methods to deal with big data in order to increase the diversity of the result set.In this paper,we firstly define the diversity of a set and the ability of an element to improve the overall diversity.Based on these definitions,we propose a diversification framework which has good performance in terms of effectiveness and efficiency.Also,this framework has theoretical guarantee on probability of success.Secondly,we design implementation algorithms based on this framework for both numerical and string data.Thirdly,for numerical and string data respectively,we carry out extensive experiments on real data to verify the performance of our proposed framework,and also perform scalability experiments on synthetic data.
文摘Area query processing is significant for various applications of wireless sensor networks since it can request information of particular areas in the monitored environment. Existing query processing techniques cannot solve area queries. Intuitively, centralized processing on Base Station can accomplish area queries via collecting information from all sensor nodes. However, this method is not suitable for wireless sensor networks with limited energy since a large amount of energy is wasted for reporting useless data. This motivates us to propose an energy-efficient in-network area query processing scheme. In our scheme, the monitored area is partitioned into grids, and a unique gray code number is used to represent a Grid ID （GID）, which is also an effective way to describe an area. Furthermore, a reporting tree is constructed to process area merging and data aggregations. Based on the properties of GIDs, subareas can be merged easily and useless data can be discarded as early as possible to reduce energy consumption. For energy-efficiently answering continuous queries, we also design an incremental update method to continuously generate query results. In essence, all of these strategies are pivots to conserve energy consumption. With a thorough simulation study, it is shown that our scheme is effective and energy-efficient
文摘Cloud computing is a very promising paradigm of service-oriented computing. One major benefit of cloud computing is its elasticity, i.e., the system＇s capacity to provide and remove resources automatically at runtime. For that, it is essential to design and implement an efficient and effective technique that takes full advantage of the system＇s potential flexibility. This paper presents a non-intrusive approach that monitors the performance of relational database management systems in a cloud infrastructure, and automatically makes decisions to maximize the efficiency of the provider＇s environment while still satisfying agreed upon ＂service level agreements＂ （SLAs）. Our experiments conducted on Amazon＇s cloud infrastructure, confirm that our technique is capable of automatically and dynamically adjusting the system＇s allocated resources observing the SLA.
基金Supported by the National Natural Science Foundation of China under Grant No. 60473077 and the Program for New Century Excellent Talents in University.
文摘In recent years there has been a significant interest in peer-to-peer （P2P） environments in the community of data management. However, almost all work, so far, is focused on exact query processing in current P2P data systems. The autonomy of peers also is not considered enough. In addition, the system cost is very high because the information publishing method of shared data is based on each document instead of document set. In this paper, abstract indices （AbIx） are presented to implement content-based approximate queries in centralized, distributed and structured P2P data systems. It can be used to search as few peers as possible but get as many returns satisfying users＇ queries as possible on the guarantee of high autonomy of peers. Also, abstract indices have low system cost, can improve the query processing speed, and support very frequent updates and the set information publishing method. In order to verify the effectiveness of abstract indices, a simulator of 10,000 peers, over 3 million documents is made, and several metrics are proposed. The experimental results show that abstract indices work well in various P2P data systems.
基金supported by the National Natural Science Foundation of China under Grant No. 61170064the National High Technology Research and Development 863 Program of China under Grant No. 2013AA013204the Tsinghua National Laboratory for Information Science and Technology (TNLIST) Cross-Discipline Foundation
文摘Multiple time series （MTS）, which describes an object in multi-dimensions, is based on single time series and has been proved to be useful. In this paper, a new analytical method called α/β-Dominant-Skyline on MTS and a formal definition of the α/β-dominant skyline MTS are given. Also, three algorithms, called NL, BC and MFB, are proposed to address the α/β-dominant skyline queries over MTS. Finally experimental results on both synthetic and real data verify the correctness and effectiveness of the proposed method and algorithms.
文摘Purpose-Resilient distributed processing technique(RDPT),in which mapper and reducer are simplified with the Spark contexts and support distributed parallel query processing.Design/methodology/approach-The proposed work is implemented with Pig Latin with Spark contexts to develop query processing in a distributed environment.Findings-Query processing in Hadoop influences the distributed processing with the MapReduce model.MapReduce caters to the works on different nodes with the implementation of complex mappers and reducers.Its results are valid for some extent size of the data.Originality/value-Pig supports the required parallel processing framework with the following constructs during the processing of queries:FOREACH;FLATTEN;COGROUP.
文摘In order to reduce the disk access time, a database can be stored on several simultaneously accessi- ble disks. In this paper, we are concerned with the dynamic d-attribute database allocation problem for range queries. An allocation method, called coordinate modulo allocation method, is proposed to al- locate data in a d-attribute database among disks so that the maximum disk accessing concurrency can be achieved for range queries. Our analysis and experiments show that the method achieves the optimum or near-optimum parallelism for range queries. The paper offers the conditions under which the method is optimal. The worst case bounds of the performance of the method are also given. In addi- tion, the parallel algorithm of processing range queries is described at the end of the paper. The meth- od has been used in the statistic and scientific database management system which is being designed by us.
文摘The idea of positional inverted index is exploited for indexing of graph database. The main idea is the use of hashing tables in order to prune a considerable portion of graph database that cannot contain the answer set. These tables are implemented using column-based techniques and are used to store graphs of database, frequent sub-graphs and the neighborhood of nodes. In order to exact checking of remaining graphs, the vertex invariant is used for isomorphism test which can be parallel implemented. The results of evaluation indicate that proposed method outperforms existing methods.
基金Supported by the National Pre-research Foundation Project of China(513150402)
文摘In hybrid wireless sensor networks,sensor mobility causes the query areas to change dynamically.Aiming at the problem of inefficiency in processing the data aggregation queries in dynamic query areas,this paper proposes a processing approach for event-based location aware queries(ELAQ),which includes query dissemination algorithm,maximum distance projection proxy selection algorithm,in-network query propagation,and aggregation algorithm.ELAQs are triggered by the events and the query results are dependent on mobile sensors'location,which are the characteristics of ELAQ model.The results show that compared with the TinyDB query processing approach,ELAQ processing approach increases the accuracy of the query result and decreases the query response time.
