Results 1 - 10 of 19

Answering SPARQL Queries over Databases under OWL 2 QL Entailment Regime

by Roman Kontchakov, Martin Rezk, Mariano Rodríguez-muro, Guohui Xiao, Michael Zakharyaschev
"... Abstract. We present an extension of the ontology-based data access platform Ontop that supports answering SPARQL queries under the OWL 2 QL direct semantics entailment regime for data instances stored in relational databases. On the theoretical side, we show how any input SPARQL query, OWL 2 QL ont ..."
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Abstract. We present an extension of the ontology-based data access platform Ontop that supports answering SPARQL queries under the OWL 2 QL direct semantics entailment regime for data instances stored in relational databases. On the theoretical side, we show how any input SPARQL query, OWL 2 QL

Semantics of SPARQL under OWL 2 Entailment Regimes

by Egor V Kostylev , Bernardo Cuenca Grau
"... Abstract. We study the semantics of SPARQL queries with optional matching features under entailment regimes. We argue that the normative semantics may lead to answers that are in conflict with the intuitive meaning of optional matching, where unbound variables naturally represent unknown informatio ..."
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Abstract. We study the semantics of SPARQL queries with optional matching features under entailment regimes. We argue that the normative semantics may lead to answers that are in conflict with the intuitive meaning of optional matching, where unbound variables naturally represent unknown

SPARQL Query Answering over OWL Ontologies

by Ilianna Kollia, Birte Glimm, Ian Horrocks
"... Abstract. The SPARQL query language is currently being extended by W3C with so-called entailment regimes, which define how queries are evaluated under more expressive semantics than SPARQL’s standard simple entailment. We describe a sound and complete algorithm for the OWL Direct Semantics entailmen ..."
Abstract - Cited by 21 (5 self) - Add to MetaCart
Abstract. The SPARQL query language is currently being extended by W3C with so-called entailment regimes, which define how queries are evaluated under more expressive semantics than SPARQL’s standard simple entailment. We describe a sound and complete algorithm for the OWL Direct Semantics

Optimizing SPARQL Query Answering over OWL Ontologies

by Ilianna Kollia, Birte Glimm
"... The SPARQL query language is currently being extended by the World Wide Web Consortium (W3C) with so-called entailment regimes. An entailment regime defines how queries are evaluated under more expressive semantics than SPARQL’s standard simple entailment, which is based on subgraph matching. The qu ..."
Abstract - Cited by 13 (4 self) - Add to MetaCart
The SPARQL query language is currently being extended by the World Wide Web Consortium (W3C) with so-called entailment regimes. An entailment regime defines how queries are evaluated under more expressive semantics than SPARQL’s standard simple entailment, which is based on subgraph matching

Answering Queries over OWL Ontologies with SPARQL

by Ilianna Kollia, Birte Glimm, Ian Horrocks
"... The SPARQL query language is currently being extended by W3C with so-called entailment regimes, which define how queries are evaluated under more expressive semantics than SPARQL’s standard simple entailment. We describe a sound and complete algorithm for the OWL Direct Semantics entailment regime ..."
Abstract - Cited by 1 (0 self) - Add to MetaCart
The SPARQL query language is currently being extended by W3C with so-called entailment regimes, which define how queries are evaluated under more expressive semantics than SPARQL’s standard simple entailment. We describe a sound and complete algorithm for the OWL Direct Semantics entailment

Towards Reconciling SPARQL and Certain Answers

by Shqiponja Ahmetaj, Tu Vienna, Wolfgang Fischl, Tu Vienna, Reinhard Pichler, Tu Vienna, Mantas Šimkus, Tu Vienna, Sebastian Skritek, Tu Vienna
"... SPARQL entailment regimes are strongly influenced by the big body of works on ontology-based query answering, notably in the area of Description Logics (DLs). However, the semantics of query answer-ing under SPARQL entailment regimes is defined in a more naive and much less expressive way than the c ..."
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-called well-designed SPARQL). Moreover, we show that the complexity of the most fundamental query analysis tasks (such as query containment and equivalence testing) is not negatively affected by the presence of OWL 2 QL entailment under the proposed semantics.

Schema-Agnostic Query Rewriting in SPARQL 1.1

by Stefan Bischof, Markus Krötzsch, Axel Polleres, Sebastian Rudolph
"... Abstract. SPARQL 1.1 supports the use of ontologies to enrich query results with logical entailments, and OWL 2 provides a dedicated fragment OWL QL for this purpose. Typical implementations use the OWL QL schema to rewrite a conjunctive query into an equivalent set of queries, to be answered agains ..."
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Abstract. SPARQL 1.1 supports the use of ontologies to enrich query results with logical entailments, and OWL 2 provides a dedicated fragment OWL QL for this purpose. Typical implementations use the OWL QL schema to rewrite a conjunctive query into an equivalent set of queries, to be answered

IOS Press Ontop: Answering SPARQL Queries over Relational Databases

by Diego Calvanese A, Benjamin Cogrel A, Sarah Komla-ebri A, Roman Kontchakov B, Davide Lanti A, Martin Rezk A, Mariano Rodriguez-muro C, Guohui Xiao A
"... Abstract. In this paper we present Ontop, an open-source Ontology Based Data Access (OBDA) system that allows for querying relational data sources through a conceptual representation of the domain of interest, provided in terms of an ontology, to which the data sources are mapped. Key features of On ..."
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SPARQL queries, R2RML mappings, and OWL 2 QL and RDFS ontologies), and its support for all major relational databases.

OWL Query Answering based on Query Extension

by Birte Glimm, Yevgeny Kazakov, Ilianna Kollia, Giorgos Stamou
"... Abstract. The paper presents an approach for optimizing query answering algo-rithms that are based on approximate instance retrieval. We consider SPARQL instance queries over OWL ontologies and use the OWL 2 Direct Semantics en-tailment regime of SPARQL for their evaluation. Approximate query answer ..."
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Abstract. The paper presents an approach for optimizing query answering algo-rithms that are based on approximate instance retrieval. We consider SPARQL instance queries over OWL ontologies and use the OWL 2 Direct Semantics en-tailment regime of SPARQL for their evaluation. Approximate query

Quest: Efficient SPARQL-to-SQL for RDF and OWL

by Mariano Rodríguez-muro, Josef Hardi, Diego Calvanese
"... Based Data Access (OBDA), where the objective is to use shared vocabularies and ontologies as means to access data living in possibly disperse and heterogenous data sources (e.g., relational DBMS, XML databases, spreadsheets, etc.) Today this task often involves an ETL process in which the data is ( ..."
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of relational DBMS and SPARQL queries, there exist several systems that allow for this on-the-fly approach, e.g., the D2RQ engine, Triplify, Spyder, Virtuoso RDF views, etc. However, often these systems fall short either in support for semantics (entailment regimes) and/or in query answering performance, e
Results 1 - 10 of 19