Learning SPARQL

Chapter 4. Copying, Creating, and Converting Data (and Finding Bad Data)

Chapter 3 described many ways to pull triples out of a dataset and to display values from those triples. In this chapter, we’ll learn how you can do a lot more than just display those values. We’ll learn about:

• Query Forms: SELECT, DESCRIBE, ASK, and CONSTRUCT: Pulling triples out of a dataset with a graph pattern is pretty much the same throughout SPARQL, and you already know several ways to do that. Besides SELECT, there are three more keywords that you can use to indicate what you want to do with those extracted triples.

• Copying Data: Sometimes you just want to pull some triples out of one collection to store in a different one. Maybe you’re aggregating data about a particular topic from several sources, or maybe you just want to store data locally so that your applications can work with that data more quickly and reliably.

• Creating New Data: After executing the kind of graph pattern logic that we learned about in the previous chapter, you sometimes have new facts that you can store. Creating new data from existing data is one of the most exciting aspects of SPARQL and the semantic web.

• Converting Data: If your application expects data to fit a certain model, and you have data that almost but not quite fits that model, converting it to triples that fit properly can be easy. If the target model is an established standard, this gives you new opportunities for integrating your data with other data and applications. ...