AGSparqlDistinct.java

package com.franz.agbase.examples;

import com.franz.agbase.*;

public class AGSparqlDistinct {

    /**
     * Demonstrates some basics of using DISTINCT 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("foaf", "http://xmlns.com/foaf/0.1/");

        // Define blank nodes
        BlankNode x = (BlankNode)ts.createBNode("_:x");
        BlankNode y = (BlankNode)ts.createBNode("_:y");
        BlankNode z = (BlankNode)ts.createBNode("_:z");
        
        // Add some data to the store
        ts.addStatement(x,"!foaf:name",ts.createLiteral("Alice"));
        ts.addStatement(x,"!foaf:mbox","<mailto:alice@example.com>");
        ts.addStatement(y,"!foaf:name",ts.createLiteral("Alice"));
        ts.addStatement(y,"!foaf:mbox","<mailto:asmith@example.com>");
        ts.addStatement(z,"!foaf:name",ts.createLiteral("Alice"));
        ts.addStatement(z,"!foaf:mbox","<mailto:alice.smith@example.com>");

        // Query first without using the DISTINCT solution modifier.
        // Note that duplicate solutions are preserved.
        String query =
        "PREFIX foaf:    <http://xmlns.com/foaf/0.1/> " +
        "SELECT ?name WHERE { ?x foaf:name ?name } ";
        
        // Query the store and show the results
        SPARQLQuery sq = new SPARQLQuery();
        sq.setTripleStore(ts);
        sq.setQuery(query);
        AGSparqlSelect.doSparqlSelect(sq);
        
        // Now query using DISTINCT
        query =
        "PREFIX foaf:    <http://xmlns.com/foaf/0.1/> " +
        "SELECT DISTINCT ?name WHERE { ?x foaf:name ?name } ";
            
        // 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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