# RDF blank node

> In RDF, it is sometimes handy to be able to talk about resources without bothering to use a global identifier. For example, we might want to state that the Mona Lisa painting has in its background an unidentified tree which we know to be a cypress tree. **A resource without a global identifier, such as the painting's cypress tree, can be represented in RDF by a blank node.** Blank nodes are like simple variables in algebra; they represent some thing without saying what their value is.[^1]

In [RDF](https://wiki.g15e.com/pages/Resource%20description%20framework.txt), it is sometimes handy to be able to talk about resources without bothering to use a global identifier. For example, we might want to state that the <Mona Lisa> painting has in its background an unidentified tree which we know to be a cypress tree. **A resource without a global identifier, such as the painting's cypress tree, can be represented in RDF by a blank node.** Blank nodes are like simple variables in algebra; they represent some thing without saying what their value is.[^1]

Blank nodes can appear in the subject and object position of a [triple](https://wiki.g15e.com/pages/RDF%20triples.txt). They can be used to denote resources without explicitly naming them with an [IRI](https://wiki.g15e.com/pages/Internationalized%20Resource%20Identifier.txt).[^1]

## Footnotes

[^1]: https://www.w3.org/TR/rdf12-primer/