XML in a Nutshell, 3rd Edition

RDF

The Resource Description Framework (RDF, http://www.w3.org/RDF/ ) can be understood as an XML encoding for a particularly simple data model. An RDF document describes resources using triples. Each triple says that a resource has a property with a value. Resources are identified by URIs. Properties can be identified by URIs or by element-qualified names. The value can be a string of plain text, a chunk of XML, or another resource identified by a URI.

The root element of an RDF document is an RDF element. Each resource the RDF element describes is represented as a Description element whose about attribute contains a URI pointing to the resource described. Each child element of the Description element represents a property of the resource. The contents of that child element are the value of that property. All RDF elements like RDF and Description are placed in the http://www.w3.org/1999/02/22-rdf-syntax-ns# namespace. Property values generally come from other namespaces.

For example, suppose we want to say that the book XML in a Nutshell has the authors W. Scott Means and Elliotte Rusty Harold. In other words, we want to say that the resource identified by the URI urn:isbn:0596002920 has one author property with the value “W. Scott Means” and another author property with the value “Elliotte Rusty Harold.” Example 7-10 does this.

Example 7-10. A simple RDF document saying that W. Scott Means and Elliotte Rusty Harold are the authors of XML in a Nutshell

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> ...