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...or a graph pattern GP, we use µ(GP) to denote the pattern obtained by 4 As in [13], disallowing GP1 and GP2 to share blank nodes is important to avoid unintended co-references. This was not needed in =-=[1,11]-=- where blank nodes were not considered.applying µ to all elements of GP in dom(µ). This convention is extended in the obvious way to filter expressions, and to all functions that are defined on varia...

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...are relevant for query answering is finite. This would not be the case if new entailments would be required whenever a given query contains a hitherto unused IRI. This distinguishes our approach from =-=[6]-=- where a partial closure algorithm is used to decide RDFS entailment for a set of axiomatic triples based on both the given graph and the query graph. 7 Implementations may support additional datatype...

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...anticweb.org/) and the TrOWL system (http://trowl.eu/) support the CQ subset of the OWL DS regime, whereas RacerPro (http://racer-systems.com/) has its proprietary query language for CQs, called nRQL =-=[3]-=-. We are not aware of a complete implementation of the DS entailment regime. As of today, the Pellet OWL 2 DL reasoner (http://clarkparsia.com/pellet) is the most advanced system. The subset of SPARQL...

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...ded, e.g., by using regular expressions to capture the transitivity of rdfs:subClassOf. To the best of our knowledge a pure query rewriting techniques has so far only be proposed for a subset of RDFS =-=[12]-=-. A combination with materialization, however, is also possible and successfully used, e.g., to realize RDFS entailment in Sesame [17]. Modified Query Evaluation The most direct approach for implement...

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...or a graph pattern GP, we use µ(GP) to denote the pattern obtained by 4 As in [13], disallowing GP1 and GP2 to share blank nodes is important to avoid unintended co-references. This was not needed in =-=[1,11]-=- where blank nodes were not considered.applying µ to all elements of GP in dom(µ). This convention is extended in the obvious way to filter expressions, and to all functions that are defined on varia...

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...tation of the DS entailment regime. As of today, the Pellet OWL 2 DL reasoner (http://clarkparsia.com/pellet) is the most advanced system. The subset of SPARQL that Pellet supports – called SPARQL-DL =-=[16]-=- – consists of queries that can be translated into a pre-defined set of query atoms in an abstract syntax; with the semantics defined per abstract query atom. Explicitly listing admissible queries has...

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... An RDF graph is a set of RDF triples of the form (subject, predicate, object) ∈ (I ∪ RDF-B) × I × RDF-T. We normally omit “RDF” in our terminology if no confusion is likely, and we use Turtle syntax =-=[2]-=- for all examples. The vocabulary Voc(G) of a graph G is the set of all terms that occur in G. Semantically, RDF graphs can be interpreted in a number of ways based on various W3C recommendations. The...

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...L semantics are known as entailment regimes. The subject of this paper is to introduce SPARQL entailment regimes for RDF and RDFS entailment [4], OWL Direct Semantics [8], and OWL RDF-Based Semantics =-=[15]-=-. The proposed extensions are part of the SPARQL 1.1 Entailment Regimes specification, which is currently being developed by the W3C SPARQL working group. 3 The goal of this paper is to provide a deta...

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...ttern are interpreted as nodes and edges of directed graphs, and the resulting query graph is matched to the data graph using variables as wild cards. Various W3C standards, including RDF [4] and OWL =-=[10]-=-, provide semantic interpretations for RDF graphs that allow additional RDF statements to be inferred from explicitly given assertions. It is desirable to utilize SPARQL as a query language in these c...

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...iting techniques has so far only be proposed for a subset of RDFS [12]. A combination with materialization, however, is also possible and successfully used, e.g., to realize RDFS entailment in Sesame =-=[17]-=-. Modified Query Evaluation The most direct approach for implementing our definitions is to modify existing SPARQL processors to evaluate BGPs differently. This can be accomplished, e.g., with the fre...

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...d by a given blank node or IRI in the input, corresponding to so-called distinguished variables in CQs. As of today, decidability of CQ entailment has only been established for a sublanguage of OWL 2 =-=[14]-=-. Restricted CQ answering still is the most common query service provided by OWL reasoners today. For example, KAON2 (http://kaon2.semanticweb.org/) and the TrOWL system (http://trowl.eu/) support the...

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...ttp://racer-systems.com/) has 9 See http://en.wikipedia.org/wiki/Triplestore for more information on the mentioned systems. its proprietary query language for CQs, called nRQL [2]. Similarly, OWLgres =-=[16]-=- and Quonto10 support the CQ fragment, but they implement the OWL QL profile, which restricts the expressivity of the input ontology to allow for a more efficient implementation based on standard data...