Programming the Semantic Web

Chapter 5. Sources of Semantic Data

You now have some tools for storing, querying, and manipulating semantic data. However, none of this is much fun if you don’t have any data to put into your triplestore. One of the longest-running criticisms of the semantic web was that no one was publishing data using the standards, so they weren’t very useful. Although this certainly held true for a while, these days many more applications, particularly in the social web application realm, are beginning to publish data using semantic web standards.

In this chapter, we will demonstrate how you can obtain and use semantic data from various sources. In doing so, we will also introduce standard vocabularies for describing social networks, music, and movies.

At the end of this chapter, we’ll explore Freebase, a semantically enabled social database that provides strong identifiers for millions of entities and vocabularies for hundreds of subject matter domains.

Friend of a Friend (FOAF)

In the previous chapter we introduced FOAF files as an example of how to show the structure of RDF. The FOAF namespace is used to represent information about people, such as their names, birthdays, pictures, blogs, and especially the other people that they know. Thus FOAF files are particularly good for representing data that appears on social networks, and several social networks allow you to access data about their users as FOAF files.

For example, here’s a file from hi5, one of the largest social networks worldwide, ...