AGSparqlUnions.java
package com.franz.agbase.examples;
import com.franz.agbase.*;
public class AGSparqlUnions {
/**
* Demonstrates some basics of using UNION 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 any namespaces
ts.registerNamespace("dc10", "http://purl.org/dc/elements/1.0/");
ts.registerNamespace("dc11", "http://purl.org/dc/elements/1.1/");
// Define blank nodes
BlankNode a = (BlankNode)ts.createBNode("_:a");
BlankNode b = (BlankNode)ts.createBNode("_:b");
BlankNode c = (BlankNode)ts.createBNode("_:c");
// Add some data to the store
ts.addStatement(a,"!dc10:title",ts.createLiteral("SPARQL Query Language Tutorial"));
ts.addStatement(a,"!dc10:creator",ts.createLiteral("Alice"));
ts.addStatement(b,"!dc11:title",ts.createLiteral("SPARQL Protocol Tutorial"));
ts.addStatement(b,"!dc11:creator",ts.createLiteral("Bob"));
ts.addStatement(c,"!dc10:title",ts.createLiteral("SPARQL"));
ts.addStatement(c,"!dc11:title",ts.createLiteral("SPARQL (Updated)"));
// This query finds titles of the books in the data, whether the title
// is recorded using Dublin Core properties from version 1.0 or version 1.1.
String query =
"PREFIX dc10: <http://purl.org/dc/elements/1.0/> " +
"PREFIX dc11: <http://purl.org/dc/elements/1.1/> " +
"SELECT ?title " +
"WHERE { { ?book dc10:title ?title } UNION { ?book dc11:title ?title } }";
// Query the store and show the results
SPARQLQuery sq = new SPARQLQuery();
sq.setTripleStore(ts);
sq.setQuery(query);
AGSparqlSelect.doSparqlSelect(sq);
// This query will only match a book if it has both a title and creator
// predicate from the same version of Dublin Core.
query =
"PREFIX dc10: <http://purl.org/dc/elements/1.0/> " +
"PREFIX dc11: <http://purl.org/dc/elements/1.1/> " +
"SELECT ?title ?author " +
"WHERE { { ?book dc10:title ?title . ?book dc10:creator ?author } " +
"UNION " +
"{ ?book dc11:title ?title . ?book dc11:creator ?author } " +
"}";
// Query the store and show the results
sq.setQuery(query);
AGSparqlSelect.doSparqlSelect(sq);
// Close the triple store and disconnect from the server.
ts.closeTripleStore();
ags.disable();
}
}
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