Expressive capabilities description languages and query rewriting algorithms

Vassalos, Vasilis; Papakonstantinou, Yannis

doi:10.1016/s0743-1066(99)00026-6

Cited by 35 publications

(40 citation statements)

References 19 publications

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“…Since our focus is on practical algorithms, we propose a PTIME algorithm for id-based support that is sound for any XPath query, and becomes complete under fairly permissive restrictions on the query, without further restricting the language of the views. Our results are in stark contrast with previous results in the relational setting [9,16], where already the simple language of conjunctive queries leads to EXPTIME completeness of expressivity and support [6], but on the other hand is closed under intersection, which poses no additional problem.…”

Section: Introductioncontrasting

confidence: 99%

“…Expressibility and support were studied in the past for relational queries and sets of relational views specified by Datalog programs [9,16,6]. The work on relational views [6] shares with our paper the idea of grouping the views in a finite number of equivalence classes w.r.t their behavior in a rewriting algorithm.…”

Section: Related Workmentioning

confidence: 90%

“…relational setting [9,16,6], but has not been addressed for sources that publish XML data (as is the case for most current Web Services). Since our focus is on practical algorithms, we consider sources that make XML data available through sets of views belonging to an XPath fragment for which the basic building blocks of rewriting algorithms, namely containment and equivalence, are tractable [11].…”

Section: Introductionmentioning

confidence: 99%

“…Expressibility and support. As in the literature on sources exporting sets of legal relational queries [16,6], we consider two settings for query answering. The first one is when the client query has to be fully answered by asking one legal query over the source, with no post-processing of its result.…”

Section: Introductionmentioning

confidence: 99%

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Efficient rewriting of XPath queries using Query Set Specifications

et al. 2009

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We study the problem of querying XML data sources that accept only a limited set of queries, such as sources accessible by Web services which can implement very large (potentially infinite) families of XPath queries. To compactly specify such families of queries we adopt the Query Set Specifications [14], a formalism close to context-free grammars.We say that query Q is expressible by the specification P if it is equivalent to some expansion of P. Q is supported by P if it has an equivalent rewriting using some finite set of P's expansions. We study the complexity of expressibility and support and identify large classes of XPath queries for which there are efficient (PTIME) algorithms. Our study considers both the case in which the XML nodes in the results of the queries lose their original identity and the one in which the source exposes persistent node ids.

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Section: Introductioncontrasting

confidence: 99%

Section: Related Workmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Efficient rewriting of XPath queries using Query Set Specifications

et al. 2009

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“…In the dependency-free setting, [23] improves the upper bound for support of [15] to non-deterministic exponential time in the combined query and program size. However for practical purposes this still yields implementations that run in doubly-exponential time.…”

Section: Related Workmentioning

confidence: 99%

Querying Data Sources that Export Infinite Sets of Views

2010

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We study the problem of querying data sources that accept only a limited set of queries, such as sources accessible by Web services which can implement very large (potentially infinite) families of queries. We revisit a classical setting in which the application queries are conjunctive queries and the source accepts families of conjunctive queries specified as the expansions of a (potentially recursive) Datalog program.We say that query Q is expressible by the program P if it is equivalent to some expansion of P. Q is supported by P if it has an equivalent rewriting using some finite set of P's expansions. We present the first study of expressibility and support for sources that satisfy integrity constraints, which is generally the case in practice.

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Expression of Z39.50 Supported Search Capabilities by Applying Formal Descriptions

Sfakakis

Kapidakis

2005

Research and Advanced Technology for Digital Libraries

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Expressive capabilities description languages and query rewriting algorithms

Cited by 35 publications

References 19 publications

Efficient rewriting of XPath queries using Query Set Specifications

Efficient rewriting of XPath queries using Query Set Specifications

Querying Data Sources that Export Infinite Sets of Views

Expression of Z39.50 Supported Search Capabilities by Applying Formal Descriptions

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