This example shows a SPARQL OPTIONAL query. It inserts triples that assert the following:

It then finds parent-child relationships, optionally including any grandchild (gkid) relationships.

import com.hp.hpl.jena.graph.*;
import com.hp.hpl.jena.query.*;
import oracle.rdf.kv.client.jena.*;

public class Example9
{
  
  public static void main(String[] args) throws Exception 
  {
    
String szStoreName  = args[0];
String szHostName   = args[1];
String szHostPort   = args[2];
String szModelName  = args[3];
    
// Create Oracle NoSQL connection 
OracleNoSqlConnection conn 
          = OracleNoSqlConnection.createInstance(szStoreName,
                                                 szHostName, 
                                                 szHostPort);
    
// Create model for named graph
OracleModelNoSql model 
              = OracleModelNoSql.createOracleModelNoSql(szModelName,
                                                        conn);
    
// Clear model    
model.removeAll();
    
// Get graph from model
OracleGraphNoSql graph = model.getGraph();
    
// Add triples    
graph.add(Triple.create(Node.createURI("u:John"), 
                        Node.createURI("u:parentOf"),
                        Node.createURI("u:Mary")));
    
graph.add(Triple.create(Node.createURI("u:John"), 
                        Node.createURI("u:parentOf"),
                        Node.createURI("u:Jack")));
    
graph.add(Triple.create(Node.createURI("u:Mary"), 
                        Node.createURI("u:parentOf"),
                        Node.createURI("u:Jill")));
    
String szQuery = " SELECT ?s ?o ?gkid "                     +
                 " WHERE { "                                +
                 "    ?s <u:parentOf> ?o  . "               +
                 "    OPTIONAL {?o <u:parentOf> ?gkid } "   + 
                 " } ";
    
    
System.out.println("Execute query " + szQuery);
    
Query query = QueryFactory.create(szQuery);
QueryExecution qexec = QueryExecutionFactory.create(query, model);
    
try {
      ResultSet results = qexec.execSelect();
      ResultSetFormatter.out(System.out, results, query);
    }
    
finally {
      qexec.close();
    }
    
model.close();
conn.dispose();    
  }
} 

The following are the commands to compile and run this example, as well as the expected output of the java command.

javac -classpath ./:./jena-core-2.7.4.jar:./jena-arq-2.9.4.jar: \
./sdordfnosqlclient.jar:./kvclient.jar:./xercesImpl-2.10.0.jar: \
./slf4j-api-1.6.4.jar:./slf4j-log4j12-1.6.4.jar:./log4j/1.2.16.jar: \
./jena-iri-0.9.4.jar:./xml-apis-1.4.01.jar Example9.java

javac -classpath ./:./jena-core-2.7.4.jar:./jena-arq-2.9.4.jar: \
./sdordfnosqlclient.jar:./kvclient.jar:./xercesImpl-2.10.0.jar: \
./slf4j-api-1.6.4.jar:./slf4j-log4j12-1.6.4.jar:./log4j/1.2.16.jar: \
./jena-iri-0.9.4.jar:./xml-apis-1.4.01.jar Example9 <store_name> \
<host_name> <host_port> <graph_name>
----------------------------------
| s        | o        | gkid     |
==================================
| <u:Mary> | <u:Jill> |          |
| <u:John> | <u:Jack> |          |
| <u:John> | <u:Mary> | <u:Jill> |
----------------------------------