Map ontology requestEngine module

This article presents the requestEngine module used in the second map ontology tutorial.

Overview

The requestEngine module is responsible to:

• Generate SPARQL requests using the Jena SPARQL request creation framework
• Process object responses

Specify the module interfaces

The requestEngine module has the following module configuration:

      <application name="requestEngine">
         <deployment>
            <lib url="RequestEngine.jar" />
         </deployment>
         <modules>
            <module name="requestEngine">
               <implementation path="org.da.request.RequestEngine" >
                  <initEntryPoint method="init" />
                  <defaultReceiveEntryPoint method="subscribe" />
               </implementation>            
               <interfaces>
                  <requestSend service="owlObjectRequest" uri="http://dassault-aviation.com/jena" />  
               </interfaces>
            </module>
         </modules>               
      </application>

It will be notified from the http://dassault-aviation.com/jena:owlObjectRequest service.

Code the request UI

We will create a window to ask the requests:

Several queries will be handled:

• Alerts List: the query to return the list of alerts and their type
• Waypoint Distance: the query to return the distance of a Waypoint
• Closest ATT Waypoint: the query to return the name and the distance of the closest ATT Waypoint

The associated buttons will fire a listener interface which is implemented by the module:

      public interface RequestGUIListener {
         public void queryAlertsList();

         public void queryWaypointDistance(String waypointID);

         public void queryClosestATTWaypoint();
      }      

Code the request generation

The module implements the RequestGUIListener interface:

• The queryAlertsList() method generates the query to return the list of alerts and their type
• The queryWaypointDistance(String waypointID) method generates the query to return the distance of a Waypoint
• The queryClosestATTWaypoint() method generates the query to return the name and the distance of the closest ATT Waypoint

Creating the query for the alerts list

The hand-written-query would be^[1]

See alerts requests in the first tutorial

:

      SELECT ?number ?type
      WHERE { 
         ?alarm rdf:type inav:Alarm .
         ?alarm inav:AlarmNumber ?number .
         ?alarm inav:hasAlarmType ?type .
      }    

First we will create a request with the ontology schema:

      SparqlRequest request = new SparqlRequest("inav");      

Adding the variables in the query

As you can see there are two variables in the SELECT construct. We must add these variables in the query:

      request.addSelect("number");
      request.addSelect("type");  

We also have an additional alarm variable which is used but not included in the SELECT:

      request.addAdditionalVariable("alarm");

Implementing the query triple patterns

The alarm variable is of the Alarm type:

      request.addType("alarm", "Alarm");

The alarm variable has the number variable as the AlarmNumber property:

      request.addPropertyRef("alarm", "AlarmNumber", "number");

The alarm variable has the type variable as the hasAlarmType property:

      request.addPropertyRef("alarm", "hasAlarmType", "type");    

Finalizing and invoking the query

The full code is:

      public void queryAlertsList() {
         SparqlRequest request = new SparqlRequest("inav");
         request.addSelect("number");
         request.addSelect("type");
         request.addAdditionalVariable("alarm");
      
         request.addType("alarm", "Alarm");
         request.addPropertyRef("alarm", "AlarmNumber", "number");
         request.addPropertyRef("alarm", "hasAlarmType", "type");
      
         objectRequestService.setDataStringValue("reqSchema", "inav");
         objectRequestService.setDataStringValue("query", request.toString());
         objectRequestService.invoke();      
      }

Creating the query for the waypoint distance

The hand-written-query would be (here for the WPT6 waypoint):

      SELECT ?label ?distance
      WHERE {
         ?wpt rdf:type inav:Waypoint .
         ?wpt inav:Label ?label .
         ?wpt inav:Label "WPT6" .
         ?ac rdf:type inav:Aircraft .
         ?ac inav:Label "falcon" .
         ?wpt inav:hasExactGeometry ?auto_2 .
         ?auto_2 inav:asWKT ?auto_3 .
         ?ac inav:hasExactGeometry ?auto_4 .
         ?auto_4 inav:asWKT ?auto_5 .
         BIND (geof:distance(?auto_3, ?auto_5, <http://www.opengis.net/def/uom/OGC/1.0/nauticalMile>) as ?distance)
      }

First we will create a request with the ontology schema:

      SparqlRequest request = new SparqlRequest("inav");      

Adding the variables in the query

There are two variables again in the SELECT construct. We must add these variables in the query:

      request.addSelect("label");
      request.addSelect("distance");  

We also have two additional wpt and ac variables which represent respectively the Waypoint and the Aircraft:

      request.addAdditionalVariable("wpt");
      request.addAdditionalVariable("ac");

Implementing the query triple patterns

The wpt variable represents a Waypoint:

      request.addType("wpt", "Waypoint");

We use the Waypoint ID passed as an argument to the method to specify its label. As you can see, we use a PropertyRef for the wpt variable to link to the label variable, but we also use a PropertyValue for the same variable to link to our Waypoint ID argument.

      request.addPropertyRef("wpt", "Label", "label");
      request.addPropertyValue("wpt", "Label", waypointID);

We must do the same thing for the Aircraft:

      request.addType("ac", "Aircraft");
      request.addPropertyValue("ac", "Label", "falcon");      

Implementing the geometry query

One unique construct will allow us to generate the part of the query which will compute the distance between the Waypoint and the Aircraft:

      request.addDistance("wpt", "ac", "distance", ISparqlRequest.DISTANCE_NM, true);      

Finalizing and invoking the query

The full code is:

      public void queryWaypointDistance(String waypointID) {
         SparqlRequest request = new SparqlRequest("inav");
         request.addSelect("label");
         request.addSelect("distance");
         request.addAdditionalVariable("wpt");
         request.addAdditionalVariable("ac");
      
         request.addType("wpt", "Waypoint");
         request.addPropertyRef("wpt", "Label", "label");
         request.addPropertyValue("wpt", "Label", waypointID);
         request.addType("ac", "Aircraft");
         request.addPropertyValue("ac", "Label", "falcon");
      
         request.addDistance("wpt", "ac", "distance", ISparqlRequest.DISTANCE_NM, true);
      
         objectRequestService.setDataStringValue("reqSchema", "inav");
         objectRequestService.setDataStringValue("query", request.toString());
         objectRequestService.invoke();   
      } 

Creating the query for the closest ATT waypoint

The hand-written-query would be:

      SELECT ?label ?distance
      WHERE {
         ?wpt rdf:type inav:Waypoint .
         ?wpt inav:Label ?label .
         ?wpt inav:hasWaypointType <http://localhost/INAV#ATT> .
         ?ac rdf:type inav:Aircraft .          ?ac inav:Label "falcon" .          ?wpt inav:hasExactGeometry ?auto_2 .          ?auto_2 inav:asWKT ?auto_3 .          ?ac inav:hasExactGeometry ?auto_4 .          ?auto_4 inav:asWKT ?auto_5 .          BIND (geof:distance(?auto_3, ?auto_5, <http://www.opengis.net/def/uom/OGC/1.0/nauticalMile>) as ?distance)       }       ORDER BY ASC( ?distance )       LIMIT 1?   ac rdf:type inav:Aircraft .
         ?ac i

First we will create a request with the ontology schema:

      SparqlRequest request = new SparqlRequest("inav");      

Adding the variables in the query

There are two variables again in the SELECT construct. We must add these variables in the query:

      request.addSelect("label");
      request.addSelect("distance");  

We also have two additional wpt and ac variables which represent respectively the Waypoint and the Aircraft:

      request.addAdditionalVariable("wpt");
      request.addAdditionalVariable("ac");

Implementing the query triple patterns

The wpt variable represents a Waypoint:

      request.addType("wpt", "Waypoint");

We only look for ATT Waypoint, so we will look for Waypoints which have an ATT type:

      request.addPropertyIndividualRef("wpt", "hasWaypointType", "ATT");

We use a PropertyRef for the wpt variable to link to the label variable:

      request.addPropertyRef("wpt", "Label", "label");

We must do the same thing for the Aircraft:

      request.addType("ac", "Aircraft");
      request.addPropertyValue("ac", "Label", "falcon");      

Implementing the geometry query

One unique construct will allow us to generate the part of the query which will compute the distance between the Waypoint and the Aircraft:

      request.addDistance("wpt", "ac", "distance", ISparqlRequest.DISTANCE_NM, true);      

Limit to the closest result

We will sort the results by ascending distance, and get only the first one, to get the closest:

      request.setLimit(1);
      request.setOrderBy("distance", true);  

Finalizing and invoking the query

The full code is:

      public void queryClosestATTWaypoint() {
         SparqlRequest request = new SparqlRequest("inav");
         request.addSelect("label");
         request.addSelect("distance");
         request.addAdditionalVariable("wpt");
         request.addAdditionalVariable("ac");
      
         request.addType("wpt", "Waypoint");
         request.addPropertyIndividualRef("wpt", "hasWaypointType", "ATT");
         request.addPropertyRef("wpt", "Label", "label");
         request.addType("ac", "Aircraft");
         request.addPropertyValue("ac", "Label", "falcon");
      
         request.addDistance("wpt", "ac", "distance", ISparqlRequest.DISTANCE_NM, true);
      
         request.setLimit(1);
         request.setOrderBy("distance", true);
      
         objectRequestService.setDataStringValue("reqSchema", "inav");
         objectRequestService.setDataStringValue("query", request.toString());
         objectRequestService.invoke(); 
      } 

Code the query result notification

Now we will write the code dealing with the object query result:

      public void subscribe(ServiceInstance service) {
         NamespaceKey JENA_OBJECT_REQUEST = NamespaceKey.createKey("http://dassault-aviation.com/jena", "owlObjectRequest");
         NamespaceKey key = service.getKey();
         if (key.equals(JENA_OBJECT_REQUEST)) {
           QueryResults results = (QueryResults) service.getData("response").getValue();
           handleObjectResponse(results);
         }
      }      

We will handle the notification depending on the query we sent in the handleObjectResponse(QueryResults results) method.

Handle the alert list query

First we will print the number of alerts:

      System.out.println("Number of Alerts: " + results.countResults());

Each result correspond to an Alert with two values for the number and type variables:

      QueryResults results = (QueryResults) service.getData("response").getValue();
      Iterator<QueryResults.Result> it = results.getOrderedResultsList().iterator();
      while (it.hasNext()) {
         QueryResults.Result result = it.next();
         int number = result.getValue("number").getValueAsInt();
         String type = result.getValue("type").getValueAsString();
         System.out.println("Alarm " + number + ": " + type);
      }

Handle the waypoint distance query

Here we have only one result, for which we will print the values for the label and distance variables:

      QueryResults.Result result = results.getOrderedResultsList().iterator().next();
      String label = result.getValue("label").getValueAsString();
      double distance = result.getValue("distance").getValueAsDouble();
      System.out.println("Distance of Waypoint " + label + " at " + distance + " NM");         

Handle the closest ATT waypoint query

Here we have only one result, for which we will print the values for the label and distance variables:

      QueryResults.Result result = results.getOrderedResultsList().iterator().next();
      String label = result.getValue("label").getValueAsString();
      double distance = result.getValue("distance").getValueAsDouble();
      System.out.println("Closest ATT Waypoint is " + label + " at " + distance + " NM");