Query Processing in a Mediator Based Framework for Linked Data Integration

Query Processing in a Mediator Based Framework for Linked Data Integration

Vânia M. P. Vidal (Federal University of Ceará, Brazil), José A. F. de Macêdo (Federal University of Ceará, Brazil), João C. Pinheiro (Federal University of Ceará, Brazil), Marco A. Casanova (Pontifícia Universidade Católica do Rio de Janeiro, Brazil) and Fábio Porto (Laboratório Nacional de Computação Científica, Brazil)
DOI: 10.4018/978-1-4666-2026-1.ch006
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Abstract

In this paper, the authors present a three-level mediator based framework for linked data integration. In the approach, the mediated schema is represented by a domain ontology, which provides a conceptual representation of the application. Each relevant data source is described by a source ontology, published on the Web according to the Linked Data principles. Each source ontology is rewritten as an application ontology, whose vocabulary is restricted to be a subset of the vocabulary of the domain ontology. The main contribution of the paper is an algorithm for reformulating a user query into sub-queries over the data sources. The reformulation algorithm exploits inter-ontology links to return more complete query results. The approach is illustrated by an example of a virtual store mediating access to online booksellers.
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2. A Framework For Linked Data Integration

In this section, we discuss the three-level architecture for linked data integration, which is depicted in Figure 1.

Figure 1.

Three-level architecture for linked data integration

The mediated schema is represented by a domain ontology (DO), which provides a conceptual representation of the domain (a globally shared vocabulary and a set of constraints). Each relevant data source is described by a source ontology, published on the Web according to the Linked Data principles, thereby becoming part of the Web of linked data. These source ontologies are depicted in the Web of Linked Data layer in Figure 1.

The local source schemas are accessed via wrappers, like those introduced in Berners-Lee et al. (2006) which export the local data into OWL. Each source ontology is rewritten as an application ontology (AO), whose vocabulary is restricted to be a subset of the vocabulary of the domain ontology. In Sacramento et al. (2010) we present a strategy to automatically generate such application ontologies, considering a set of local ontologies, a domain ontology and the result of the matching between each local ontology and the domain ontology. We adopt OWL Lite (Bechhofer et al., 2004) as the ontology language to represent the domain ontology, the source ontologies and the application ontologies.

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