The Semantic Web
IN THIS PART
23 RDF for Information Owners
24 The Semantic Web for Information Owners
RDF for Information Owners
IN THIS CHAPTER
• Basics of the Resource Description Framework
• The RDF Family of Specifications
• The RDF Data Model
• RDF Schema
Working with the Angle Brackets
The Resource Description Framework (RDF) gives information owners a way of expressing meaning on the Web that machines can understand (and humans will, ultimately, profit from). This chapter explains how RDF expresses machine-understandable meaning using its data model; the next chapter, on the Semantic Web, will show some of the good things that RDF makes happen. So, if you want the business case for RDF applications, skip ahead to Chapter 24, “The Semantic Web for Information Owners.” If mastery of RDF syntax and semantics is what you’re after, read on.
RDF is spelled out in a family of W3C specifications. Like many families, though, the RDF family members are not all quite at the same level of maturity, and not all of them agree with each other all the time. Therefore, to help you avoid the pitfall of spending a lot of time on parts of RDF that are either obsolete or immature, we’ll first go through the specifications, giving extra attention to open issues and resources that will keep your expertise current.
RDF’s data model gives RDF its power to express machine-understandable meaning, and that’s what we’ll look at next. Because the RDF data model is a graph, we’ll study just enough graph theory to deal with that formalism and get through the model. Then, we’ll go through the data model in detail, showing the RDF graph in both pictorial and XML syntax, all in ready-reference form. Then we’ll do the same thing for RDF schema, and you’ll see how RDF schema’s class hierarchy allows the meaning of RDF instances to be constrained and validated.
Finally, we’ll look at some angle bracket–type issues in handling RDF, such as how to embed RDF in Web pages, and so on.
Therefore, by the time you finish this chapter, your expertise will extend beyond the basics of RDF to
The RDF family of specifications
Issues with the specs and where to go to resolve them
The RDF data model (and a little graph theory)
What RDF schema validates and how it does so
XML and pictorial RDF syntax