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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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