Leveraging mediator cost models with heterogeneous data sources

Naacke, Hubert; Gardarin, Georges; Tomasic, Anthony

doi:10.1109/icde.1998.655798

Cited by 43 publications

(31 citation statements)

References 16 publications

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“…Some systems require the data sources to explicitly export the statistics required for query optimization [NGT98,ROH99]. This is not applicable to our problem of building statistics for the hidden Web, because the hidden Web data sources are autonomous and provide no information beyond answers to user queries.…”

Section: On-line Xml Statistics For the Hidden Webmentioning

confidence: 99%

Building XML statistics for the hidden web

Aboulnaga¹,

Naughton²

2003

Proceedings of the Twelfth International Conference on Information and Knowledge Management - CIKM '03

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There is currently a lot of interest in developing Internet query processors that can pose elaborate queries on XML data on the Web. Such query processors can query data sources that have static XML files, but they should also be able to query "hidden Web" data sources that export an XML view of data stored in a database. To optimize queries that involve these hidden Web data sources, we need to have XML statistics that can be used to estimate the selectivity of queries posed to these sources. Since we can only access the data at a hidden Web data source by issuing queries, we need to develop on-line XML statistics that are built by observing queries to a hidden Web data source and their result sizes.In this paper, we assume that queries to a hidden Web data source are XPath selections from a virtual XML document that represents all the data at this source. We observe the user XPath queries to the data source and convert them to a more abstract and generalized form that we call annotated path expressions. We describe an on-line statistics structure that stores such annotated path expressions and information about their selectivity for use in estimating the selectivity of future XPath queries. We experimentally demonstrate the convergence and accuracy of our proposed on-line statistics using real and synthetic XML data sets.

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Section: On-line Xml Statistics For the Hidden Webmentioning

confidence: 99%

Building XML statistics for the hidden web

Aboulnaga¹,

Naughton²

2003

Proceedings of the Twelfth International Conference on Information and Knowledge Management - CIKM '03

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“…One major challenge is that some necessary local optimization information such as local cost models may not be available at the global level. Several techniques to derive cost models for an autonomous local database system (DBS) at the global level have been proposed in the literature, including a calibration method [12,16], a query sampling method [44,45,48], a cost vector database approach [1], a fuzzy approach [47], and a generic model approach [30,36].…”

Section: Introductionmentioning

confidence: 99%

Query optimization via contention space partitioning and cost error controlling for dynamic multidatabase systems

Zhu

Haridas

Hou

2008

Distrib Parallel Databases

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A multidatabase system (MDBS) integrates information from multiple autonomous local databases. Performing global query optimization to achieve efficient query processing in such a system is challenging due to local autonomy of the data sources. Dynamic factors in the environment make the problem even more difficult. In this paper, we present two techniques, i.e., contention space partitioning and cost error controlling, to perform global query optimization in a dynamic MDBS. Both techniques generate an execution plan with multiple versions for a query in a dynamic MDBS, utilizing the multistate cost models built for the dynamic environment via our previous multistate query sampling method. The first technique partitions the contention space of a dynamic multidatabase environment into a given number of subspaces and chooses a good query execution plan version for each subspace, while the second technique selects a set of execution plan versions by using a given error tolerance to control query execution costs. Experiments demonstrate that the proposed techniques are quite promising for performing global query optimization in a dynamic MDBS. Compared with related work on dynamic query optimization, our approach has an advantage of avoiding the high overhead for modifying or regenerating an execution plan for a query based on dynamic runtime information.

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“…The first approaches to query optimization were performed in the field of multidatabases [8], where cost estimation in relational databases uses statistics of the database to compute the cost of each operator in each plan. The authors propose a combination of a generic cost model with specific information of each wrapper.…”

Section: Figure 1: Electronic Bookshop Examplementioning

confidence: 99%

Efficiently Updating Cost Repository Values for Query Optimization on Web Data Sources in a Mediator/Wrapper Environment

Hidalgo¹,

Pan

Álvarez

et al. 2006

Next Generation Information Technologies and Systems

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Abstract. Optimizing accesses to sources in a mediator/wrapper environment is a critical need. Due to a variety of reasons, relational-based optimization techniques are of no use when having to handle HTTP-based web sources, so new approaches which take into account client/server communication costs must be devised. This paper describes a cost model that stores values from a complete set of web source-focused parameters obtained by the web wrappers, by using a novel updating technique that handles the values measured by the wrappers in previous query executions, and generates a new model instance in each new iteration with an efficient processing cost. This instance allows rapid value updates caused by changes of the server quality or bandwidth, so typical in this context. The results of these techniques are demonstrated both theoretically and by means of an implementation showing how performance improves in real-world web sources when compared to classical approaches.

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Leveraging mediator cost models with heterogeneous data sources

Cited by 43 publications

References 16 publications

Building XML statistics for the hidden web

Building XML statistics for the hidden web

Query optimization via contention space partitioning and cost error controlling for dynamic multidatabase systems

Efficiently Updating Cost Repository Values for Query Optimization on Web Data Sources in a Mediator/Wrapper Environment

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