Formalisation and experiences of R2RML-based SPARQL to SQL query translation using morph

Abstract

R2RML is used to specify transformations of data avail able in relational databases into materialised or virtual RDF datasets. SPARQL queries evaluated against virtual datasets are translated into SQL queries according to the R2RML mappings, so that they can be evaluated over the underly ing relational database engines. In this paper we describe an extension of a well-known algorithm for SPARQL to SQL translation, originally formalised for RDBMS-backed triple stores, that takes into account R2RML mappings. We present the result of our implementation using queries from a synthetic benchmark and from three real use cases, and show that SPARQL queries can be in general evaluated as fast as the SQL queries that would have been generated by SQL experts if no R2RML mappings had been used.

Ewya: An Interoperable Fog Computing Infrastructure with RDF Stream Processing

“…Efficient SPARQL-to-SQL translation has been investigated by RodriguezMuro et al [14] and Priyatna et al [13]. The state-of-the-art reduces redundant self-joins and applies query containment and semantic query optimisation to translations.…”

Answering SPARQL Queries over Databases under OWL 2 QL Entailment Regime

“…A number of translations of SPARQL queries (under simple entailment) to SQL queries have already been suggested in the literature; see, e.g., [9,13,7,32,27]. However, none of them is suitable for our aims because they do not take into account the three-valued logic used in the OPTIONAL and BOUND constructs of the current SPARQL 1.1 (the semantics of OPTIONAL was not compositional in SPARQL 1.0).…”

“…A variant of such a transformation has been suggested in [27]. Here we develop the idea first presented in [28].…”

“…by means of an ontology which provides the user with a convenient query vocabulary, hides the structure of the data sources, and can enrich incomplete data with background knowledge. About a dozen OBDA systems have been implemented in both academia and industry; e.g., [27,30,24,4,23,15,12,8,20,22]. Most of them support conjunctive queries and the OWL 2 QL profile of OWL 2 as the ontology language (or its generalisations to existential datalog rules).…”

morph-LDP: An R2RML-Based Linked Data Platform Implementation

“…However, there are contexts in which organizations are interested in continuing with their existing relational databases instead of transforming data into an RDF format and managing it from a triple store. Hence, the work that has been done in the past at W3C on the definition of the R2RML language, as well as the implementations available that support such language (e.g., Ontop [1], morph-RDB [2], D2R [3]), may be useful as an alternative implementation for LDP, as shown in Figure 1.…”