Querying the Semantic Web—SPARQL

Abstract

RDF provides a simple way to represent distributed data. The triple is the simplest way to represent a named connection between two things. But a representation of data is useless without some means of accessing that data. The standard way to access RDF data uses a query language called SPARQL. SPARQL stands for SPARQL Protocol And RDF Query Language. The SPARQL query language works closely with the structure of RDF itself. SPARQL query patterns are represented in a variant of Turtle. The queried RDF graph can be created from one kind of data or merged from many; in either case, SPARQL is the way to query it. This chapter gives examples of the SPARQL query language. Most of the examples are based on version 1.0 of the standard. SPARQL is a query language and shares many features with other query languages like XQUERY and SQL. But it differs from each of these query languages in important ways. SPARQL queries can be used to fetch information (like SQL queries) or to transform a graph into a new form (like rules). Both forms use the same notion of graph pattern to specify the desired information.