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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