Content Syndication with RSS

Resource Description Framework

This system of defining everything with URIs, and using this to describe the relationships between things, has been formalized in a system known as the Resource Description Framework (RDF). In this section, we’ll look at enough RDF to give us a head start on the rest of the book. For a much deeper insight into RDF, take a look at Shelley Powers’ Practical RDF (O’Reilly).

Because RDF is quite abstract — its ability to be written in different ways notwithstanding — in this chapter we are going to look at what the RDF developers call the “data model,” which we can call “the really simple version, in pictures.”

Resources, PropertyTypes, and Properties

As before, within the data model anything (an object, a person, a document, a concept, a section of a document, etc.) can have a URI. In RDF we call anything addressable with a URI a resource.

Some resources can be used as properties of other resources. For example, the concept of “Author” has a URI of its own (all concepts can), and other resources can have a property of “author”. Such resources are called PropertyTypes.

A property is the combination of a resource, a PropertyType, and a value. For example, “The Author of Content Syndication with RSS is Ben Hammersley.” The value can be a string (“Ben Hammersley” in the previous example), or it can be another resource—for example, “Ben Hammersley (resource) has a home page (PropertyType) at http://www.benhammersley.com (resource).”

Nodes and Arcs

RDF’s ...