2.3. SPARQL query processing

RDF has become a de facto standard for publishing information and knowledge on the Web. Compared to other standards such as XML or JSON, RDF facilitates in particular the integration of information by linking RDF resources of separate data sets through owl:sameAs, rdf:type, and rdfs:subClassOf properties. The resulting Semantic Web of linked open data (LOD) sets is composed of billions of triples, and building systems for efficiently storing and querying the Semantic Web is a technological and scientific challenge reminiscent of other Big Data applications.

2.3.1. SPARQL with and without RDF/S entailment

The first challenge concerns the interaction between SPARQL’s graph pattern matching semantics and RDF’s data model semantics defined by the RDF/S entailment rules. There mainly exist two solutions to evaluating a query Q over a data set D and a set of entailment rules R. The first solution is to first saturate D by recursively applying all...