Translation of Heterogeneous Databases into RDF, and Application to the Construction of a SKOS Taxonomical Reference

Abstract

Abstract. While the data deluge accelerates, most of the data produced remains locked in deep Web databases. For the linked open data to benefit from the potential represented by this huge amount of data, it is crucial to come up with solutions to expose heterogeneous databases as linked data. The xR2RML mapping language is an endeavor towards this goal: it is designed to map various types of databases to RDF, by flexibly adapting to heterogeneous query languages and data models while remaining free from any specific language. It extends R2RML, the W3C recommendation for the mapping of relational databases to RDF, and relies on RML for the handling of various data formats. In this paper we present xR2RML, we analyse data models of several modern databases as well as the format in which query results are returned, and we show how xR2RML translates any result data element into RDF, relying on existing languages such as XPath and JSONPath when necessary. We illustrate some features of xR2RML such as the generation of RDF collections and containers, and the ability to deal with mixed data formats. We also describe a real-world use case in which we applied xR2RML to build a SKOS thesaurus aimed at supporting studies on History of Zoology, Archaeozoology and Conservation Biology.

Leveraging Web of Things W3C Recommendations for Knowledge Graphs Generation

“…We implemented our approach in two RML processors, the RMLMapper 18 and RMLStreamer 19 , to show that our approach can be applied to any implementation following the RML specification. The RMLMapper follows a mapping-driven approach by executing each Triples Map one by one to generate a single knowledge graph.…”

“…Such mapping languages describe how processors should access various heterogeneous data sources except for Web APIs and streams. RML leverages the Hydra vocabulary to provide access to Web APIs [7], SPARQL-Generate and xR2RML define each their own approach to accomplish this [15,19]. However, they can only perform HTTP GET requests without authentication to retrieve data from the Web.…”

“…Web APIs. While mapping languages have preliminary support for Web APIs [7,15,19], they do not consider defining authentication, or protocolspecific features such as custom HTTP headers or other HTTP methods besides HTTP GET. As mentioned in Section 3.1, we encountered this issue when accessing Web APIs in our ESSENCE use case.…”

Bridging the Semantic Web and NoSQL Worlds: Generic SPARQL Query Translation and Application to MongoDB

“…The xR2RML mapping language [25] intends to foster the translation of legacy data sources into RDF. It can describe the mapping of an extensible scope of databases to RDF, independently of any query language or data model.…”

“…In previous works we defined a generic mapping language, xR2RML [25], that enables the translation of a broad scope of data sources into RDF. The mapping instructs how to translate each data item from its original format into RDF triples, by adapting to the multiplicity of query languages and data models.…”