This presentation covers the semantics of SPARQL queries with optional matching features under entailment regimes. It argues that normative semantics may lead to answers that are in conflict with the intuitive meaning of optional matching, where unbound variables naturally represent unknown information. The presenters propose 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. They argue that this solution comes at no cost for regimes with an entailment relation of reasonable complexity and that it preserves the known properties of optional matching that are commonly exploited for static analysis and optimization.

Keywords: Entailment regimes, Unbound variable, Normative semantics, Web Ontology Language (OWL), Strict semantics
Author: Kostylev, Egor
Date created: 2014-12-19 05:00:00.000
Time required: P15M

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