BlankNodes

Blank Nodes

Also known as: "bNodes"

Nodes in an RDF graph that have no URI label.

Blank nodes describe a thing without naming it. I can describe a person "brown hair, interested in bicycle racing, lives in China" without naming them, and often that description is useful. I can even attempt to identify a particular person - "the guy who wrote the book 100 Years of Solitude" - so that we can try to be sure if we are talking about the same person.

Uniquely Identifying bNodes with nodeID

You can identify BlankNodes locally with a NodeId. that ID can be used to talk about the node inside your particular file/store of information, but you can't use it to ID the node externally.

This can be convenient because the NodeId can be a short, human readable, name. Whereas assigning a full URI involves some work.

Uniquely Identifying bNodes by InverseFunctionProperty

BlankNodes can be uniquely identified if they make use of a predicate (SubjectPredicateObject) that has the "InverseFunctionalProperty." That means that the predicate and the object are guaranteed to uniquely identify the subject (the blank node.)

See Also

• discussion in the RDF Concepts document
• Blank Nodes as Existential Variables in the RDF Semantics spec

Discussion

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