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School of Computer Science and Technology, Huazhong University of Science and Technology, Wuhan, China moh [email protected], [email protected] 2 Faculty of Engineering and IT, University of Technology Sydney, Sydney, Australia [email protected] 3 Computer Science, IBB University, Ibb, Yemen [email protected] Computer Science, Najran University-Sharurah, Najran, Saudi Arabia

Abstract. For integrating relational databases (RDBs) into semantic web applications, the W3C RDB2RDF Working Group recommended two approaches, Direct Mapping (DM) and R2RML. The DM provides a set of mapping rules according to RDB schema, while the R2RML allows users to manually define mappings according to existing target ontology. The major problem to use R2RML is the effort for creating R2RML mapping documents manually. This may lead to appearance of many mistakes in the R2RML documents and requires domain experts. In this paper, we propose and implement an approach to generate an R2RML mapping documents automatically from RDB schema. The R2RML mapping reflects the behavior of the DM specification and allows any R2RML parser to generate a set of RDF triples from relational data. The input of generating approach is DBsInfo class that automatically generated from relational schema. An experimental prototype is developed and shows the effectiveness of our approach algorithms. Keywords: Relational Database to Resource Description Framework (RDB2RDF) · Direct Mapping · R2RML · Relational database · Resource Description Framework (RDF)

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Introduction

The continuous explosion of resource description framework (RDF) data opens door for new innovations in big data, social network analysis, and semantic web initiatives, which can be shared and reused through the application, enterprise and community boundaries. The semantic web [1] is one of the most important research fields that aim to construct a web of data based on the RDF [2] c Springer Science+Business Media Singapore 2016  W. Che et al. (Eds.): ICYCSEE 2016, Part I, CCIS 623, pp. 151–169, 2016. DOI: 10.1007/978-981-10-2053-7 15

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data model. It allows data to be shared and reused through applications, enterprise and community boundaries. Relational databases (RDBs) are the primary sources of web data, “deep web” [3]. The main reason is one of the studies [3] showed that internet accessible databases contained up to 500 times more data compared to the static web, and roughly 70 % of websites are backed by RDBs. The W3C RDB2RDF Working Group recently recommended a specification for languages to map RDB (data and schemas) to RDF and OWL, tentatively called Direct Mapping (DM) [4] and R2RML (Relational Database to RDF Mapping Language) [5]. However, the W3C Working Group does not recommend any implementation for DM and R2RML. The DM provides a set of automatic mapping rules to construct an ontology schema (RDF(S) and OWL) from RDB schema and convert relational data to RDF graphs according to that schema [6]. The ontology constructed reflects the structure and co