Chapter 2. RDF: the data model for Linked Data
This chapter covers
- An introduction to the Resource Description Framework
- RDF as a data model for Linked Data
- RDF formats relevant to Linked Data
- Linked Data vocabularies
Linked Data couldn’t exist without a consistent underlying data model. That data model is the Resource Description Framework (RDF). Some people have negative opinions about RDF because they consider it to be overly complicated. Those opinions were generally formed in the early days of RDF and relate to its first, and rather complicated, serialization format based on XML. We hope to show you that RDF is quite simple and introduce you to the variety of different serialization formats that make modern RDF easy to use.
We briefly introduced RDF in chapter 1 and mentioned that a single RDF statement describes two things and a relationship between them. Multiple RDF statements can connect to form graphs (not just hierarchies) of information. The only thing that might make RDF seem complicated is that most things and the relationships use URIs to name them.[1] RDF statements may be hard to read in the raw because URIs can be long. Fortunately, many RDF serialization formats have ways to write abbreviations for long URIs.
1 RDF 1.1 changed URIs to IRIs (Internationalized Resource Identifiers) in 2013. For our purposes, we generally mean the same thing when we say URI or IRI; the differences are subtle. When in doubt, remember that modern RDF and hence Linked Data use IRIs.