This paper studies the semantics of SPARQL queries with optional matching features under entailment regimes. It argues that the normative semantics may lead to answers that are in conflict with the intuitive meaning of optional matching, where unbound variables naturally represent unknown information. It proposes an extension of the SPARQL algebra that addresses these issues and is compatible with any entailment regime satisfying the minimal requirements given in the normative specification.

URL: http://www.cs.ox.ac.uk/files/6665/SPARQL-ISWC.pdf
Keywords: Basic Graph Pattern (BGP), SPARQL, Entailment Regimes, Optional matching
Author: Grau, Bernardo Cuenca
Language: http://id.loc.gov/vocabulary/iso639-2/eng
Time required: P30M
Educational use: instruction
Educational audience: teacher-educationSpecialist
Interactivity type: expositive

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