RDF does this with a very simple model for describing the relationship between an object, called a node and some piece of information about it, called a property. The property is given context by a node subset called a PropertyType
An object is referenced by its location, described by its Uniform Resource Identifier (URI). URLs are one type of URIs and is described by its properties. So, the authorship of an article called "RDF Emerges in Metadata Explosion" in the online newspaper called The Foo York Times, written by Lance Foobar could be described like this:
As you can see from this simple example, the basic idea of RDF is that "resources (URIs)" have "properties (canonical values)" that consist of "propertyTypes (Author, Title, etc.)". These values are called triples.
If we add another property and PropertyType of the URI above so that it reads like this:
[http://www.fooyorktimes.com/RDF.html] --->Title--->"RDF Emerges in Metadata Explosion"
|--->Author-->"Lance Foobar"
Then this set of multiple triples is known as a "description." Descriptions can also be nodes, so that collections of properties for a URI can be referenced as a single thing that itself has properties. Descriptions, all of the properties that are used to describe them and the canonical value of the properties together are known as a Bag.
PropertyTypes are based on specific named elements that are defined in schemas and will require the Namespace specification that is also being worked on by the W3C. Namespaces are needed to avoid having two PropertyTypes with the same name, but different semantics.
As it stands now, RDF will be expressed in XML in something like the following:
What this is saying is the same thing as the diagrams above, but the RDF expression in XML also shows how the particular semantics for "Lance Foobor is the writer of http://www.fooyorktimes.com/RDF.html" knows what a writer is. In this case it is getting the RDF semantics from the linked schema called RDF and getting the semantics for Writer from the Foo York Times' page WhoWeAre.html.
This is confusing, I know, but most likely RDF will not be written or consumed by hand. It will be a way for applications to automatically parse XML data and also have some smarts about how to organize the structured content.
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