Authors:
Franck Michel
;
Catherine Faron-Zucker
and
Johan Montagnat
Affiliation:
University Nice Sophia Antipolis - CNRS, France
Keyword(s):
Linked Data, Query rewriting, SPARQL, RDF, NoSQL, xR2RML.
Abstract:
Fostering the development of SPARQL interfaces to heterogeneous databases is a key to efficiently expose
legacy data as RDF on the Web. To deal with the variety of modern database formats and query languages,
this paper describes a two-step approach to translate a SPARQL query into an equivalent target database query.
First, given an xR2RML mapping describing how native database entities can be mapped to RDF, a SPARQL
query is translated into a pivot abstract query language independent of the database. In a second step, the pivot
query is translated into the target database query language, considering the specific database capabilities. The
paper focuses on the first step of the query translation, from SPARQL to a pivot query that takes into account
join constraints and SPARQL filters, and embeds conditions entailed by matching SPARQL graph patterns
with relevant mappings. It discusses the query optimisations that can be implemented at this level, and briefly
describes an application
to the case of MongoDB, a NoSQL document store.
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