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Pontifical Catholic University of Rio de Janeiro

1. YENIER TORRES IZQUIERDO. [en] KEYWORD SEARCH OVER FEDERATED RDF GRAPHS BY EXPLORING THEIR SCHEMAS.

Degree: 2017, Pontifical Catholic University of Rio de Janeiro

[pt] O Resource Description Framework (RDF) foi adotado como uma recomendação do W3C em 1999 e hoje é um padrão para troca de dados na Web. De fato, uma grande quantidade de dados foi convertida em RDF, muitas vezes em vários conjuntos de dados fisicamente distribuídos ao longo de diferentes localizações. A linguagem de consulta SPARQL (sigla do inglês de SPARQL Protocol and RDF Query Language) foi oficialmente introduzido em 2008 para recuperar dados RDF e fornecer endpoints para consultar fontes distribuídas. Uma maneira alternativa de acessar conjuntos de dados RDF é usar consultas baseadas em palavras-chave, uma área que tem sido extensivamente pesquisada, com foco recente no conteúdo da Web. Esta dissertação descreve uma estratégia para compilar consultas baseadas em palavras-chave em consultas SPARQL federadas sobre conjuntos de dados RDF distribuídos, assumindo que cada conjunto de dados RDF tem um esquema e que a federação tem um esquema mediado. O processo de compilação da consulta SPARQL federada é explicado em detalhe, incluindo como computar o conjunto de joins externos entre as subconsultas locais geradas, como combinar, com a ajuda de cláusulas UNION, os resultados de consultas locais que não têm joins entre elas, e como construir a cláusula TARGET, de acordo com a composição da cláusula WHERE. Finalmente, a dissertação cobre experimentos com dados do mundo real para validar a implementação.

[en] The Resource Description Framework (RDF) was adopted as a W3C recommendation in 1999 and today is a standard for exchanging data in the Web. Indeed, a large amount of data has been converted to RDF, often as multiple datasets physically distributed over different locations. The SPARQL Protocol and RDF Query Language (SPARQL) was officially introduced in 2008 to retrieve RDF datasets and provide endpoints to query distributed sources. An alternative way to access RDF datasets is to use keyword-based queries, an area that has been extensively researched, with a recent focus on Web content. This dissertation describes a strategy to compile keyword-based queries into federated SPARQL queries over distributed RDF datasets, under the assumption that each RDF dataset has a schema and that the federation has a mediated schema. The compilation process of the federated SPARQL query is explained in detail, including how to compute a set of external joins between the local subqueries, how to combine, with the help of the UNION clauses, the results of local queries which have no external joins between them, and how to construct the TARGET clause, according to the structure of the WHERE clause. Finally, the dissertation covers experiments with real-world data to validate the implementation.

Advisors/Committee Members: MARCO ANTONIO CASANOVA, MARCO ANTONIO CASANOVA.

Subjects/Keywords: [pt] ESQUEMA MEDIADO; [en] MEDIATED SCHEMA; [pt] RDF; [en] RDF; [pt] BUSCA POR PALAVRAS-CHAVE; [en] KEYWORD SEARCH; [pt] DADOS CONECTADOS; [en] LINKED DATA; [pt] SPARQL; [en] SPARQL; [pt] CONSULTAS FEDERADAS; [en] FEDERATED QUERY

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APA (6th Edition):

IZQUIERDO, Y. T. (2017). [en] KEYWORD SEARCH OVER FEDERATED RDF GRAPHS BY EXPLORING THEIR SCHEMAS. (Thesis). Pontifical Catholic University of Rio de Janeiro. Retrieved from http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=30739

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

IZQUIERDO, YENIER TORRES. “[en] KEYWORD SEARCH OVER FEDERATED RDF GRAPHS BY EXPLORING THEIR SCHEMAS.” 2017. Thesis, Pontifical Catholic University of Rio de Janeiro. Accessed August 23, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=30739.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

IZQUIERDO, YENIER TORRES. “[en] KEYWORD SEARCH OVER FEDERATED RDF GRAPHS BY EXPLORING THEIR SCHEMAS.” 2017. Web. 23 Aug 2017.

Vancouver:

IZQUIERDO YT. [en] KEYWORD SEARCH OVER FEDERATED RDF GRAPHS BY EXPLORING THEIR SCHEMAS. [Internet] [Thesis]. Pontifical Catholic University of Rio de Janeiro; 2017. [cited 2017 Aug 23]. Available from: http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=30739.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

IZQUIERDO YT. [en] KEYWORD SEARCH OVER FEDERATED RDF GRAPHS BY EXPLORING THEIR SCHEMAS. [Thesis]. Pontifical Catholic University of Rio de Janeiro; 2017. Available from: http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=30739

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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