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ObjectGlobe: Ubiquitous query processing on the Internet

VLDB JOURNAL 2001年第1期10卷 48-71页

作者： Braumandl, R Keidl, M Kemper, A Kossmann, D Kreutz, A Seltzsam, S Stocker, K Univ Passau Lehrstuhl Informat D-94030 Passau Germany Tech Univ Munich Inst Informat D-81667 Munich Germany

We present the design of ObjectGlobe, a distributed and open query processor for Internet data sources. Today, data is published on the Internet via Web servers which have, if at all, very localized query processing capabilities. The goal of the ObjectGlobe project is to establish an open marketplace in which data and query processing capabilities can be distributed and used by any kind of Internet application. Furthermore, ObjectGlobe integrates cycle providers (i.e., machines) which carry out query processing operators. The overall picture is to make it possible to execute a query with-in principle-unrelated query operators, cycle providers, and data sources. Such an infrastructure can serve as enabling technology for scalable e-commerce applications, e.g., B2B and B2C market places. to be able to integrate data and data processing operations of a large number of participants. One of the main challenges in the design of such an open system is to ensure privacy and security. We discuss the ObjectGlobe security requirements, show how basic components such as the optimizer and runtime system need to be extended, and present the results of performance experiments that assess the additional cost for secure distributed query processing. Another challenge is quality of service management so that users can constrain the costs and running times of their queries.

关键词： distributed query processing query optimization open systems cycle-, function- and data provider security privacy quality of service

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Tuple source relational model: A source-aware data model for multidatabases

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DATA & KNOWLEDGE ENGINEERING 1999年第1期29卷 83-114页

作者： Lim, EP Chiang, RHL Cao, YY Nanyang Technol Univ Sch Accountancy & Business Informat Management Res Ctr Singapore 639798 Singapore Nanyang Technol Univ Sch Appl Sci Ctr Adv Informat Syst Singapore 639798 Singapore

In some integration projects, complete integration of database instances may not be necessary. It may also be too costly and impossible to do so due to poor local data quality and insufficient instance-level knowledge. In this research, we study how multidatabases with global schemas should be represented and manipulated when the data instances from the local databases do not require to be fully integrated. We propose the tuple source (TS) relational model to represent multidatabases under such an integration requirement. This model extends the classical relational model by augmenting every relation with a source attribute to identify the local database that the tuples come from. The source attribute can also be used to specify the right context to interpret global data instances. To manipulate TS relations, we have developed a set of tuple source relational algebraic operations and an extended SQL query language known as TS-SQL. With TS relational model, flexible multidatabase queries that involve instances from different local databases can be formulated easily. In this paper, we also reported our distributed query processing and optimization strategies and their implementation. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： database integration multidatabases relational data model distributed query processing

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Dynamic query operator scheduling for wide-area remote access

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distributed AND PARALLEL DATABASES 1998年第3期6卷 217-246页

作者： Amsaleg, L Franklin, MJ Tomasic, A Inst Natl Rech Informat & Automat IRISA F-35042 Rennes France Univ Maryland Dept Comp Sci College Pk MD 20742 USA INRIA Rocquencourt F-78153 Le Chesnay France

distributed databases operating over wide-area networks such as the Internet must deal with the unpredictable nature of the performance of communication. The response times of accessing remote sources can vary widely due to network congestion, link failure, and other problems. In such an unpredictable environment, the traditional iterator-based query execution model performs poorly. We have developed a class of methods, called query scrambling, for dealing explicitly with the problem of unpredictable response times. query scrambling dynamically modifies query execution plans on-the-fly in reaction to unexpected delays in data access. In this paper we focus on the dynamic scheduling of query operators in the context of query scrambling. We explore various choices for dynamic scheduling and examine, through a detailed simulation, the effects of these choices. Our experimental environment considers pipelined and non-pipelined join processing in a client with multiple remote data sources and delayed or possibly bursty arrivals of data. Our performance results show that scrambling rescheduling is effective in hiding the impact of delays on query response time for a number of different delay scenarios.

关键词： distributed query processing mediators iterator execution model performance analysis query scrambling dynamic query optimization

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Adaptive algorithms for join processing in distributed database systems

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distributed AND PARALLEL DATABASES 1997年第3期5卷 233-269页

作者： Scheuermann, P Chong, EI ORACLE CORP NEW ENGLAND R&D CTR NASHUA NH 03062 USA

distributed query processing algorithms usually perform data reduction by using a semijoin program, but the problem with these approaches is that they still require an explicit join of the reduced relations in the final phase. We introduce an efficient algorithm for join processing in distributed database systems that makes use of bipartite graphs in order to reduce data communication costs and local processing costs. The bipartite graphs represent the tuples that can be joined in two relations taking also into account the reduction state of the relations. This algorithm fully reduces the relations at each site. We then present an adaptive algorithm for response time optimization that takes into account the system configuration, i.e., the additional resources available and the data characteristics, in order to select the best strategy for response time minimization. We also report on the results of a set of experiments which show that our algorithms outperform a number of the recently proposed methods for total processing time and response time minimization.

关键词： distributed query processing join algorithms adaptive algorithms bipartite graphs

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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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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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Combinatorial optimization of distributed queries

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 1995年第6期7卷 915-927页

作者： Groselj, B Malluhi, QM UNIV SW LOUISIANA CTR ADV COMP STUDIESLAFAYETTELA 70504

In relational distributed databases a query cost consists of a local cost and a transmission cost. query optimization is a combinatorial optimization problem, As the query size grows, the optimization methods based on exhaustive search become too expensive, We propose the following strategy for solving large distributed query optimization problems in relational database systems: 1) represent each query-processing schedule by a labeled directed graph, 2) reduce the number of different schedules by pruning away invalid or high-cost solutions, and 3) find a suboptimal schedule by combinatorial optimization, We investigate several combinatorial optimization techniques: random search, single start, multistart, simulated annealing, and a combination of random search and local simulated annealing. The utility of combinatorial optimization is demonstrated in the problem of finding the (sub)optimal semijoin schedule that fully reduces all relations of a tree query, The combination of random search and local simulated annealing was superior to other tested methods.

关键词： combinatorial optimization distributed query processing multistart random search relational database semi-join simulated annealing single start tree query

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SECURITY CONSTRAINT processing IN A MULTILEVEL SECURE distributed DATABASE-MANAGEMENT SYSTEM

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 1995年第2期7卷 274-293页

作者： THURAISINGHAM, B FORD, W MITRE Corporation Bedford MA USA The MITRE Corporation McLean VA US Mitre Corp. Bedford MA USA

In a multilevel secure distributed database management system, users cleared at different security levels access and share a distributed database consisting of data at different sensitivity levels. An approach to assigning sensitivity levels, also called security levels, to data is one which utilizes constraints or classification rules. Security constraints provide an effective classification policy, They can be used to assign security levels to the data based on content, context, and time. In this paper we extend our previous work on security constraint processing in a centralized multilevel secure database management system by describing techniques for processing security constraints in a distributed environment during query, update, and database design operations.

关键词： MULTILEVEL SECURE distributed DATABASE MANAGEMENT SYSTEM SECURITY CONSTRAINTS INFERENCE PROBLEM SECURITY POLICY distributed query processing distributed UPDATE processing MULTILEVEL distributed DATABASE DESIGN

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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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DECLARE and SDS: Early efforts to commercialize deductive database technology

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The VLDB Journal 1994年第2期3卷 211-243页

作者： Kleßling, Werner Schmidt, Helmut Strauß, Werner Dünzinger, Gerhard Lehrstuhl für Informatik 2 Universität Augsburg Augsburg D-86135 Universitätsstraße 8 Germany Süddt.Finanzsoftware GmbH Mering D-86415 Reifersbrunner Str. 26 PECOM Unternehmensberatung GmbH München D-81547 Otkerstr. 7b Germany ABLAY Optimierung GmbH Gilching D-82205 Schmidgern 1 Germany

The Smart Data System (SDS) and its declarative query language, Declarative Reasoning, represent the first large-scale effort to commercialize deductive database technology. SDS offers the functionality of deductive reasoning in a distributed, heterogeneous database environment. In this article we discuss several interesting aspects of the query compilation and optimization process. The emphasis is on the query execution plan data structure and its transformations by the optimizing rule compiler. Through detailed case studies we demonstrate that efficient and very compact runtime code can be generated. We also discuss our experiences gained from a large pilot application (the MVV-expert) and report on several issues of practical interest in engineering such a complex system, including the migration from Lisp to C. We argue that heuristic knowledge and control should be made an integral part of deductive databases. © 1994 VLDB.

关键词： Declarative reasoning distributed query processing heuristic control multi-databases productization query optimizer

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