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AGSparqlUnions.java

package com.franz.ag.examples;



import com.franz.ag.*;



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

        AGUtils.doSparqlSelect(ts, query);

        

        // 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

        AGUtils.doSparqlSelect(ts, query);

            

        // Close the triple store and disconnect from the server.

        ts.closeTripleStore();

        ags.disable();

    }



}
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