Added unit tests for the event abstractions.
Added Element as the notion of common ancestry between Device and Host.
diff --git a/net/api/src/main/java/org/onlab/onos/net/device/DeviceService.java b/net/api/src/main/java/org/onlab/onos/net/device/DeviceService.java
index 4048fbb..ac2f4a4 100644
--- a/net/api/src/main/java/org/onlab/onos/net/device/DeviceService.java
+++ b/net/api/src/main/java/org/onlab/onos/net/device/DeviceService.java
@@ -3,6 +3,10 @@
 import org.onlab.onos.net.Device;
 import org.onlab.onos.net.DeviceId;
 import org.onlab.onos.net.MastershipRole;
+import org.onlab.onos.net.Port;
+import org.onlab.onos.net.PortNumber;
+
+import java.util.List;
 
 /**
  * Service for interacting with the inventory of infrastructure devices.
@@ -34,7 +38,21 @@
     Device getDevice(DeviceId deviceId);
 
 
-//    List<Port> getPorts(DeviceId deviceId);
+    /**
+     * Returns the list of ports associated with the device.
+     *
+     * @param deviceId device identifier
+     * @return list of ports
+     */
+    List<Port> getPorts(DeviceId deviceId);
+
+    /**
+     * Returns the port with the specified number and hosted by the given device.
+     * @param deviceId device identifier
+     * @param portNumber port number
+     * @return device port
+     */
+    Port getPort(DeviceId deviceId, PortNumber portNumber);
 
     /**
      * Adds the specified device listener.
@@ -49,4 +67,5 @@
      * @param listener device listener
      */
     void removeListener(DeviceListener listener);
+
 }