Blank node
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In RDF, a blank node (also called bnode) is a node in an RDF graph representing a resource for which a URI or literal is not given. The resource represented by a blank node is also called an anonymous resource. According to the RDF standard a blank node can only be used as subject or object of an RDF triple.
In RDF, a blank node (also called bnode) is a node in an RDF graph representing a resource for which a URI or literal is not given. The resource represented by a blank node is also called an anonymous resource. According to the RDF standard a blank node can only be used as subject or object of an RDF triple. ==Notation in serialization formats== Blank nodes can be denoted through blank node identifiers in the following formats, RDF/XML, RDFa, Turtle, N3 and N-Triples. The following example shows how it works in RDF/XML. The blank node identifiers are only limited in scope to a serialization of a particular RDF graph, i.e. the node _:b in the subsequent example does not represent the same node as a node named _:b in any other graph. Blank nodes can also be denoted through nested elements (in RDF/XML, RDFa, Turtle and N3). Here is the same triples with the above. Below is the same example in RDFa. Web Data Alice Carol Below is the same example in Turtle. PREFIX ex: ex:title "Web Data" ; ex:professor [ ex:fullName "Alice Carol" ; ex:homePage ] ; . ex:title "Web Data" ; ex:professor _:entity ; ex:students _:students ; ex:generatedBy _:activity1 . _:entity ex:fullName "Alice Carol" ; ex:homePage ; ex:hasAddress _:address . _:address a ex:Address ; ex:streetAddress "123 Main St." ; ex:postalCode "A1A1A1" ; ex:addressLocality "London" . _:students a rdf:Bag ; ex:hasMember _:s1 ; ex:hasMember _:s2 . _:activity1 a ex:Event; ex:creator _:entity ; ex:atTime "Tuesday 11 February, 06:51:00 CST" . _:activity2 a ex:Event, ex:Update ; ex:actionOver _:activity1 ; ex:creator _:entity2 ; ex:atTime "Monday 17 February, 08:12:00 CST" . 1 ===Entailment checking=== Regarding the entailment problem it is proved that (a) deciding simple or RDF/S entailment of RDF graphs is NP-Complete, and (b) deciding equivalence of simple RDF graphs is Isomorphism-Complete. ==See also== FOAF Open-world assumption ==References==
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