RDF is about making machine-processable statements. To make these kinds of statements suitable for processing by machines, two things are needed: - a system of machine-processable identifiers for identifying a subject, predicate, or object in a statement without any possibility of confusion with a similar-looking identifier that might be used by someone else on the Web. - a machine-processable language for representing these statements and exchanging them between machines.

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The Web provides a more general form of identifier for these purposes, called the Uniform Resource Identifier (URI). URLs are a particular kind of URI.