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RDF Blank Nodes

It would be easy to extrapolate a lot of meaning about blank nodes but, bottom line, a blank node represents a resource that isn’t currently identified. As with the infamous null value from the relational data model, there could be two reasons why the identifying URI is absent: either the value will never exist (isn’t meaningful) or the value could exist but doesn’t at the moment (currently missing).

Most commonly, a blank node—known as a bnode, or occasionally anonymous node—is used when a resource URI isn’t meaningful. An example of this could be a representation of a specific individual (since most of us don’t think of humans with URIs).

In RDF/XML, a blank node is represented by an oval (it is a resource), with either no value in the oval or a computer-generated identifier. The RDF/XML Validator generates an identifier, which it uses within the blank node to distinguish it from other blank nodes within the graph. Most tools generate an identifier for blank nodes to differentiate them.


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