The RDF Triple In RDF, the fundamental way
The RDF Triple In RDF, the fundamental way to conceptualize a fact is through the RDF Triple. To convey a fact, three pieces of information are needed: a subject, a property, and a value. To express a fact, you need these three pieces of information. In the following example, the subject is chapter, the property is author, and the value is Andrew Watt. This chapter has the author Andrew Watt To express the same notion in a more generalized, abstract way, consider this: [The subject] has [a property] with this [value] The subject is the thing being described; in this case the subject is this chapter. In RDF jargon, the subject is a resource. The property is some characteristic of the resource. For example, it might be an attribute of the resource, or some relationship of the resource. In RDF jargon the property is called a predicate. The value corresponds to a value of the predicate. In RDF jargon the value is called the object. So, you can rewrite the preceding generalized form as [The resource] has a [predicate] with this [object]. For many newcomers to RDF the jargon does get in the way. If you find it easy to think that a subject has a property with a particular value, you might initially find it difficult to think in terms of a resource having a predicate with an object. Personally, I find it much more natural to think in terms of subject, property, and value. But whoever said that computing was natural? Now that you know the terms that RDF uses for the concepts that are part of the simple statement, This chapter has the author Andrew Watt how can you identify which chapter you are talking about? It s fine to use the term This chapter inside this chapter, but how can you refer in an unambiguous way to this chapter from other chapters inside this book or other books or other places that aren t books at all? To solve this problem, RDF uses URIs. Using URIs in RDF URIs are used to identify resources. So how can you use a URI to help identify which chapter you mean by the term this chapter ? What URI should be used? This book is published by Wrox Press. So, in constructing a URI, it seems a good choice to start with http://www.wrox.com. Of course Wrox publishes many books. So you need a way to identify the book. Using the last six digits of the ISBN, 579169, seems a reasonable approach. 113 RDF: The Resource Description Framework