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distributed query processing in flash-based sensor networks

中国高等学校学术文摘·计算机科学 2008年第3期2卷 248-256页

作者： Jianliang XU Xueyan TANG Wang-Chien LEE Department of Computer Science and Engineering Hong Kong Baptist UniversityHong KongChina School of Computer Engineering Nanyang Technological UniversitySingapore 639798Singapore Department of Computer Science and Engineering Pennsylvania State UniversityPhiladelphiaPA 16802USA

Wireless sensor networks are used in a large array of applications to capture,collect,and analyze physical environmental *** existing sensor systems instruct sensor nodes to report their measurements to central repositories outside the network,which is expensive in energy *** technological advances in flash memory have given rise to the development of storagecentric sensor networks,where sensor nodes are equipped with high-capacity flash memory storage such that sensor data can b.e stored and managed inside the network to reduce expensive *** novel architecture calls for new data management techniques to fully exploit distributed in-network data *** paper describes some of our research on distributed query processing in such flash-based sensor *** particular interests are the issues that arise in the design of storage management and indexing structures combining sensor system workload and read/write/erase characteristics of flash memory.

关键词： distributed query processing wireless sensor network flash storage indexing

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distributed query processing in the presence of blank nodes

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SEMANTIC WEB 2017年第6期8卷 1001-1021页

作者： Stolpe, Audun Halvorsen, Jonas Norwegian Def Res Estab FFI Postboks 25 N-2027 Kjeller Norway Univ Oslo Oslo Norway

This paper demonstrates that the presence of blank nodes in RDF data represents a problem for distributed processing of SPARQL queries. It is shown that the usual decomposition strategies from the literature will leak information - even when information derives from a single source. It is argued that this leakage, and the proper reparational measures, need to be accounted for in a formal semantics. To this end a set semantics for SPARQL is generalized with a parameter representing execution contexts. This makes it possible to keep tabs on the naming of blank nodes across execution contexts, which in turn makes it possible to articulate a decomposition strategy that is provably sound and complete wrt. any selection of RDF sources even when blank nodes are allowed. Alas, this strategy is not computationally tractable. However, there are ways of utilizing knowledge about the sources, if one has it, that will help considerably.

关键词： SPARQL federation distributed query processing logical foundation completeness decomposition scheme

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distributed query processing on the grid

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INTERNATIONAL JOURNAL OF HIGH PERFORMANCE COMPUTING APPLICATIONS 2003年第4期17卷 353-367页

作者： Smith, J Gounaris, A Watson, P Paton, NW Fernandes, AAA Sakellariou, R Newcastle Univ Dept Comp Sci EPSRC Project High Performance Query Proc Grid Newcastle Upon Tyne NE1 7RU Tyne & Wear England Univ Manchester Dept Comp Sci Manchester M13 9PL Lancs England

distributed query processing (DQP) has been widely used in data intensive applications where data of relevance to users are stored at multiple locations. This paper argues: (i) that DQP can be important in the Grid, as a means of providing high-level, declarative languages for integrating data access and analysis;and (ii) that the Grid provides resource management facilities that are useful to developers of DQP systems. As well as discussing and illustrating how DQP technologies can be deployed within the Grid, the paper describes Polar*, a prototype implementation of a DQP system running over Globus. Polar* can handle complex data by adopting the ODMG object model and its query language OQL, which supports the invocation of user-defined operations. The Globus components are accessed through the MPICH-G interface rather than in a lower level way. A case study from bioinformatics is used throughout the paper, to show the benefits of the approach.

关键词： grid computing distributed query processing parallel query processing user-defined operation globus MPI ODMG

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distributed query processing on the grid

Distributed query processing on the grid

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3rd International Workshop on Grid Computing

关键词： grid computing distributed query processing parallel query processing user-defined operation globus MPI ODMG

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Extension of the one-shot semijoin strategy to minimize data transmission cost in distributed query processing

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INFORMATION SCIENCES 1999年第1-4期114卷 1-21页

作者： Najjar, F Slimani, Y Fac Sci Tunis Dept Informat Tunis 1060 Tunisia

The optimization of general queries in a distributed database management system is an important and challenging research issue. The problem is to find an optimal evaluation strategy for a given general query. In this paper, we propose an approach based on a combination of join and parallel semijoin operations to minimize the amount of data transmission in distributed query processing. First, we describe an efficient distributed query processing strategy using only semijoins. This strategy selects an optimal set instead of a sequence of semijoins to be executed in parallel in three phases: a projection phase, a transmission phase and a reduction phase. Then, we apply a sequence of joins as reducers for query processing. Furthermore, we consider the problem of finding an optimal general sequence that fully reduces a general join query graph. We present a new method that combines parallel and sequential semijoins. We report on experiments that show that our approach based on parallel semijoins is not only efficient but also effective in reducing the total amount of data transmission required to process distributed queries. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： distributed query processing multi-join semijoin profitable semijoins parallel semijoin data filter operation

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COMBINING JOIN AND SEMI-JOIN OPERATIONS FOR distributed query-processing

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 1993年第3期5卷 534-542页

作者： CHEN, MS YU, PS IBM Thomas J. Watson Research Center Yorktown Heights NY USA

In this paper, we explore the approach to applying a combination of join and semi-join operations to minimize the amount of data transmission required for distributed query processing. Specifically, we identify and exploit two important concepts which occur with the use of join operations as reducers in query processing, namely, gainful semi-joins and pure join attributes. Some semi-joins, though not profitable themselves, may benefit the execution of subsequent join operations, and become profitable owing to the use of join operations as reducers. Such a semi-join is termed a gainful semi-join. In addition, join attributes which are not part of the output attributes are referred to as pure join attributes. We shall not only exploit the usefulness of gainful semi-joins, but also utilize the removability of pure join attributes to reduce the amount of data transmission required for query processing. Moreover, in light of the two concepts, heuristic searches are developed to determine a sequence of join and semi-join reducers for query processing. Our results show the importance of the approach to combining joins and semi-joins for distributed query processing.

关键词： distributed query processing GAINFUL SEMIJOINS PURE JOIN ATTRIBUTES A-ASTERISK-ALGORITHM

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distributed rrays: an algebra for generic distributed query processing

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distributed AND PARALLEL DATABASES 2021年第4期39卷 1009-1064页

作者： Gueting, Ralf Hartmut Behr, Thomas Nidzwetzki, Jan Kristof Fernuniv Fac Math & Comp Sci D-58084 Hagen Germany

We propose a simple model for distributed query processing based on the concept of a distributed array. Such an array has fields of some data type whose values can be stored on different machines. It offers operations to manipulate all fields in parallel within the distributed algebra. The arrays considered are one-dimensional and just serve to model a partitioned and distributed data set. distributed arrays rest on a given set of data types and operations called the basic algebra implemented by some piece of software called the basic engine. It provides a complete environment for query processing on a single machine. We assume this environment is extensible by types and operations. Operations on distributed arrays are implemented by one basic engine called the master which controls a set of basic engines called the workers. It maps operations on distributed arrays to the respective operations on their fields executed by workers. The distributed algebra is completely generic: any type or operation added in the extensible basic engine will be immediately available for distributed query processing. To demonstrate the use of the distributed algebra as a language for distributed query processing, we describe a fairly complex algorithm for distributed density-based similarity clustering. The algorithm is a novel contribution by itself. Its complete implementation is shown in terms of the distributed algebra and the basic algebra. As a basic engine the Secondo system is used, a rich environment for extensible query processing, providing useful tools such as main memory M-trees, graphs, or a DBScan implementation.

关键词： distributed database distributed query processing Density-based similarity clustering

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INTERLEAVING A JOIN SEQUENCE WITH SEMIJOINS IN distributed query-processing

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IEEE TRANSACTIONS ON PARALLEL AND distributed SYSTEMS 1992年第5期3卷 611-621页

作者： CHEN, MS YU, PS IBM Thomas J. Watson Research Center Yorktown Heights NY USA

In distributed query processing, the conventional approach to reduce the amount of data transmission is to first apply a sequence of semijoins as "reducers" and then ship the resultant relations to the final site to carry out the join operations. Recently, it has been shown that the approach of applying a combination of joins and semijoins as reducers can lead to substantially larger reduction on data transmission required. In this paper, we develop an efficient heuristic approach to determine an effective sequence of semijoin and join reducers. Semijoins whose execution will reduce the amount of data transmission required to perform a join sequence are termed beneficial semijoins for that join sequence. Note that beneficial semijoins include the conventional profitable semijoins and the gainful semijoins that are not profitable themselves but become beneficial due to the inclusion of join reducers. This type of dependency between semijoin and join reducers complicates the identification of beneficial semijoins and the ordering in the reducer sequence. We first obtain a sequence of join reducers and map it into a join sequence tree. In light of the join sequence tree, we derive important properties of beneficial semijoins. These properties are then applied to develop an efficient algorithm to determine the beneficial semijoins which can be inserted into the join sequence. Our results show that the approach of interleaving a join sequence with beneficial semijoins are not only efficient but also effective in reducing the total amount of data transmission required to process distributed queries.

关键词： BENEFICIAL SEMIJOINS distributed query processing GAINFUL SEMIJOINS JOIN SEQUENCE TREE REDUCIBLE SET

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Efficient distributed query processing

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IEEE TRANSACTIONS ON AUTOMATION SCIENCE AND ENGINEERING 2016年第3期13卷 1230-1246页

作者： Kolcun, Roman Boyle, David E. McCann, Julie A. Imperial Coll London Dept Elect & Elect Engn London SW7 2AZ England Imperial Coll London Dept Comp London SW7 2AZ England

A variety of wireless networks, including applications of Wireless Sensor Networks, Internet of Things, and Cyber-physical Systems, increasingly pervade our homes, retail, transportation systems, and manufacturing processes. Traditional approaches communicate data from all sensors to a central system, and users (humans or machines) query this central point for results, typically via the web. As the number of deployed sensors, and thus generated data streams, is increasing exponentially, this traditional approach may no longer be sustainable or desirable in some application contexts. Therefore, new approaches are required to allow users to directly interact with the network, for example, requesting data directly from sensor nodes. This is difficult, as it requires every node to be capable of point-to-point routing, in addition to identifying a subset of nodes that can fulfil a user's query. This paper presents DRAGON, a platform that allows any node in the network to identify all nodes that satisfy user queries, i.e., request data from nodes, and relay the result to the user. The DRAGON platform achieves this in a fully distributed way. No central orchestration is required, network overheads are low, and latency is improved over existing comparable methods. DRAGON is evaluated on networks of various topologies and different network densities. It is compared with the state-of-the-art algorithms based on summary trees, like Innet and SENS-Join. DRAGON is shown to outperform these approaches up to 88% in terms of network traffic required, also a proxy for energy efficiency, and 84% in terms of processing delay. Note to Practitioners-This work is motivated by the continuing deluge of constrained, wirelessly connected sensing and control devices. Networks of communicable sensors and actuators are finding increased applicability across a range of industries and application scenarios. They are often thought of as a subset of the '"nternet of Things." However, due to the inh

关键词： Autonomous and automated sensing and control systems cyber-physical systems distributed query processing distributed storage routing algorithm wireless sensor networks

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A GRAPH-THEORETICAL APPROACH TO DETERMINE A JOIN REDUCER SEQUENCE IN distributed query-processing

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 1994年第1期6卷 152-165页

作者： CHEN, MS YU, PS IBM Thomas J. Watson Research Center Yorktown Heights NY USA

Semijoin has traditionally been relied upon to reduce the cost of data transmission for distributed query processing. However, judiciously applying join operations as reducers can lead to further reduction in the amount of data transmission required. In view of this fact, we explore in this paper the approach of using join operations as reducers in distributed query processing. We shall first show that the problem of determining a sequence of join operations for a query can be transformed to that of finding a specific type of set of cuts to the corresponding query graph, where a cut to a graph is a partition of nodes in that graph. Then, in light of this concept, we shall prove that the problem of determining the optimal sequence of join operations for a given query graph is of exponential complexity, thus justifying the necessity of applying heuristic approaches to solve this problem. By mapping the problem of determining a sequence of join reducers into the one of finding a set of cuts, we develop (for tree and general query graphs, respectively) efficient heuristic algorithms to determine a join reducer sequence for distributed query processing. The algorithms developed are based on the concept of divide and conquer and are of polynomial time complexity. Simulation is performed to evaluate these algorithms.

关键词： distributed query processing JOIN REDUCERS, COMPLETE AND FEASIBLE CUTS DIVIDE AND CONQUER GRAPH PARTITION

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