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I build an ontology in protege tool which resulting good knowledge representation when seen in webOwl software. But when I listed all triplets using SPARQL query, i was finding huge number of blank nodes. Can any one say the reason. Is there any problem in model or blank nodes are common.

Umasrinivas
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    OWL != RDF and SPARQL is the query language for RDF. OWL class expressions/axioms are quite often represented by a set of RDF triples, thus, blank nodes will be used to model n-ary relations. See the [RDF mapping of OWL](https://www.w3.org/TR/owl2-mapping-to-rdf/) – UninformedUser Sep 05 '18 at 18:56
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    Also, blank nodes can represent anonymous individuals in Aboxes; and they can be used for reification in RDF/XML, e.g., when annotating axioms. So, yes - they can be very common. – Ignazio Sep 06 '18 at 01:00

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