The RDF data model
The Turtle language we used in Example 2-7 is a human-readable format for RDF data. Sometimes RDF is also written in an XML format, which does the same thing much more verbosely—see Example 2-8. Turtle/N3 is preferable as it is much easier on the eyes, and tools like Apache Jena  can automatically convert between different RDF formats if necessary.
RDF has a few quirks due to the fact that it is designed for internet-wide data exchange. The subject, predicate, and object of a triple are often URIs. For example, a predicate might be an URI such as