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LDQL: A query language for the Web of Linked Data
Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
University of Chile, Chile; Chilean Centre Semant Web Research, Chile.
2016 (English)In: Journal of Web Semantics, ISSN 1570-8268, E-ISSN 1873-7749, Vol. 41Article in journal (Refereed) Published
Abstract [en]

The Web of Linked Data is composed of tons of RDF documents interlinked to each other forming a huge repository of distributed semantic data. Effectively querying this distributed data source is an important open problem in the Semantic Web area. In this paper, we propose LDQL, a declarative language to query Linked Data on the Web. One of the novelties of LDQL is that it expresses separately (i) patterns that describe the expected query result, and (ii) Web navigation paths that select the data sources to be used for computing the result. We present a formal syntax and semantics, prove equivalence rules, and study the expressiveness of the language. In particular, we show that LDQL is strictly more expressive than all the query formalisms that have been proposed previously for Linked Data on the Web. We also study some computability issues regarding LDQL. We first prove that when considering the Web of Linked Data as a fully accessible graph, the evaluation problem for LDQL can be solved in polynomial time. Nevertheless, when the limited data access capabilities of Web clients are considered, the scenario changes drastically; there are LDQL queries for which a complete execution is not possible in practice. We formally study this issue and provide a sufficient syntactic condition to avoid this problem; queries satisfying this condition are ensured to have a procedure to be effectively evaluated over the Web of Linked Data. (C) 2016 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV , 2016. Vol. 41
Keyword [en]
Linked Data; Query language; Foundations; SPARQL; Queries
National Category
Computer Science
Identifiers
URN: urn:nbn:se:liu:diva-133742DOI: 10.1016/j.websem.2016.10.001ISI: 000389584600002OAI: oai:DiVA.org:liu-133742DiVA: diva2:1063119
Note

Funding Agencies|Millennium Nucleus Center for Semantic Web Research [NC120004]; Fondecyt [1140790]

Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2017-01-25

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The full text will be freely available from 2018-10-29 15:19
Available from 2018-10-29 15:19

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CiteExportLink to record
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