package com.franz.ag.examples;
import com.franz.ag.*;
public class AGSparqlBlankNodeLabels {
/**
* Demonstrates some basics of blank node labels in SPARQL
*
* @param args unused
* @throws AllegroGraphException
*/
public static void main(String[] args) throws AllegroGraphException {
// Connect to server, which must already be running.
AllegroGraphConnection ags = new AllegroGraphConnection();
try {
ags.enable();
} catch (Exception e) {
throw new AllegroGraphException("Server connection problem", e);
}
// Create fresh triple-store for this example.
AllegroGraph ts = ags.renew("sparql", AGPaths.TRIPLE_STORES);
// Register the foaf namespace
ts.registerNamespace("foaf", "http://xmlns.com/foaf/0.1/");
// Define blank nodes
BlankNode a = (BlankNode)ts.createBNode("_:a");
BlankNode b = (BlankNode)ts.createBNode("_:b");
// Add some data to the store
ts.addStatement(a,"!foaf:name",ts.createLiteral("Alice"));
ts.addStatement(b,"!foaf:name",ts.createLiteral("Bob"));
// A query showing blank node labels
String query =
"PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
"SELECT ?x ?name " +
"WHERE { ?x foaf:name ?name }";
// Query the store and show the results
// Note that the labels on blank nodes can be different than
// those supplied above. There need not be any relation
// between a label _:a in the result set and a blank node
// in the data graph with the same label.
AGUtils.doSparqlSelect(ts, query);
// Close the triple store and disconnect from the server.
ts.closeTripleStore();
ags.disable();
}
}