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/event/AbstractListenerManager.java b/net/api/src/main/java/org/onlab/onos/event/AbstractListenerManager.java
index 7d4836f..d063b59 100644
--- a/net/api/src/main/java/org/onlab/onos/event/AbstractListenerManager.java
+++ b/net/api/src/main/java/org/onlab/onos/event/AbstractListenerManager.java
@@ -51,8 +51,13 @@
         }
     }
 
-    @Override
-    public void reportProblem(E event, Throwable error) {
+    /**
+     * Reports a problem encountered while processing an event.
+     *
+     * @param event event being processed
+     * @param error error encountered while processing
+     */
+    protected void reportProblem(E event, Throwable error) {
         log.warn("Exception encountered while processing event " + event, error);
     }
 
diff --git a/net/api/src/main/java/org/onlab/onos/event/AbstractEventSinkBroker.java b/net/api/src/main/java/org/onlab/onos/event/DefaultEventSinkBroker.java
similarity index 91%
rename from net/api/src/main/java/org/onlab/onos/event/AbstractEventSinkBroker.java
rename to net/api/src/main/java/org/onlab/onos/event/DefaultEventSinkBroker.java
index 4ca3c3c..c791544 100644
--- a/net/api/src/main/java/org/onlab/onos/event/AbstractEventSinkBroker.java
+++ b/net/api/src/main/java/org/onlab/onos/event/DefaultEventSinkBroker.java
@@ -12,7 +12,7 @@
 /**
  * Base implementation of event sink broker.
  */
-public class AbstractEventSinkBroker implements EventSinkBroker {
+public class DefaultEventSinkBroker implements EventSinkBroker {
 
     private final Map<Class<? extends Event>, EventSink<? extends Event>> sinks =
             new ConcurrentHashMap<>();
@@ -36,6 +36,7 @@
     @Override
     @SuppressWarnings("unchecked")
     public <E extends Event> EventSink<E> getSink(Class<E> eventClass) {
+        // TODO: add implicit registration of descendant classes
         return (EventSink<E>) sinks.get(eventClass);
     }
 
diff --git a/net/api/src/main/java/org/onlab/onos/event/EventSink.java b/net/api/src/main/java/org/onlab/onos/event/EventSink.java
index f46458c..45ad408 100644
--- a/net/api/src/main/java/org/onlab/onos/event/EventSink.java
+++ b/net/api/src/main/java/org/onlab/onos/event/EventSink.java
@@ -12,12 +12,4 @@
      */
     void process(E event);
 
-    /**
-     * Reports a problem encountered while processing an event.
-     *
-     * @param event event being processed
-     * @param error error encountered while processing
-     */
-    void reportProblem(E event, Throwable error);
-
 }
diff --git a/net/api/src/main/java/org/onlab/onos/net/Device.java b/net/api/src/main/java/org/onlab/onos/net/Device.java
index 700654f..9e6018e 100644
--- a/net/api/src/main/java/org/onlab/onos/net/Device.java
+++ b/net/api/src/main/java/org/onlab/onos/net/Device.java
@@ -1,11 +1,9 @@
 package org.onlab.onos.net;
 
-import org.onlab.onos.net.provider.Provided;
-
 /**
  * Representation of a network infrastructure device.
  */
-public interface Device extends Provided {
+public interface Device extends Element {
 
     /**
      * Coarse classification of the type of the infrastructure device.
diff --git a/net/api/src/main/java/org/onlab/onos/net/DeviceId.java b/net/api/src/main/java/org/onlab/onos/net/DeviceId.java
index 45528a4..124fa96 100644
--- a/net/api/src/main/java/org/onlab/onos/net/DeviceId.java
+++ b/net/api/src/main/java/org/onlab/onos/net/DeviceId.java
@@ -1,49 +1,19 @@
 package org.onlab.onos.net;
 
 import java.net.URI;
-import java.util.Objects;
-
-import static com.google.common.base.Objects.toStringHelper;
 
 /**
  * Immutable representation of a device identity.
  */
-public class DeviceId {
-
-    private final URI uri;
-
-    public DeviceId(URI uri) {
-        this.uri = uri;
-    }
+public class DeviceId extends ElementId {
 
     /**
-     * Returns the backing URI.
+     * Creates a device id using the supplied URI.
      *
-     * @return backing device URI
+     * @param uri backing device URI
      */
-    public URI uri() {
-        return uri;
-    }
-
-    @Override
-    public int hashCode() {
-        return Objects.hash(uri);
-    }
-
-    @Override
-    public boolean equals(Object obj) {
-        if (this == obj) {
-            return true;
-        }
-        if (obj == null || getClass() != obj.getClass()) {
-            return false;
-        }
-        final DeviceId other = (DeviceId) obj;
-        return Objects.equals(this.uri, other.uri);
-    }
-    @Override
-    public String toString() {
-        return toStringHelper(this).add("uri", uri).toString();
+    public DeviceId(URI uri) {
+        super(uri);
     }
 
 }
diff --git a/net/api/src/main/java/org/onlab/onos/net/Element.java b/net/api/src/main/java/org/onlab/onos/net/Element.java
new file mode 100644
index 0000000..c11d103
--- /dev/null
+++ b/net/api/src/main/java/org/onlab/onos/net/Element.java
@@ -0,0 +1,17 @@
+package org.onlab.onos.net;
+
+import org.onlab.onos.net.provider.Provided;
+
+/**
+ * Base abstraction of a network element, i.e. an infrastructure device or an end-station host.
+ */
+public interface Element extends Provided {
+
+    /**
+     * Returns the network element identifier.
+     *
+     * @return element identifier
+     */
+    ElementId id();
+
+}
diff --git a/net/api/src/main/java/org/onlab/onos/net/ElementId.java b/net/api/src/main/java/org/onlab/onos/net/ElementId.java
new file mode 100644
index 0000000..e0f3add
--- /dev/null
+++ b/net/api/src/main/java/org/onlab/onos/net/ElementId.java
@@ -0,0 +1,55 @@
+package org.onlab.onos.net;
+
+import java.net.URI;
+import java.util.Objects;
+
+import static com.google.common.base.Objects.toStringHelper;
+
+/**
+ * Immutable representation of a network element identity.
+ */
+public class ElementId {
+
+    private final URI uri;
+
+    /**
+     * Creates an element identifier using the supplied URI.
+     *
+     * @param uri backing URI
+     */
+    public ElementId(URI uri) {
+        this.uri = uri;
+    }
+
+    /**
+     * Returns the backing URI.
+     *
+     * @return backing URI
+     */
+    public URI uri() {
+        return uri;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(uri);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        final ElementId other = (ElementId) obj;
+        return Objects.equals(this.uri, other.uri);
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this).add("uri", uri).toString();
+    }
+
+}
diff --git a/net/api/src/main/java/org/onlab/onos/net/Host.java b/net/api/src/main/java/org/onlab/onos/net/Host.java
index f8e2e31..17eaf22 100644
--- a/net/api/src/main/java/org/onlab/onos/net/Host.java
+++ b/net/api/src/main/java/org/onlab/onos/net/Host.java
@@ -1,14 +1,21 @@
 package org.onlab.onos.net;
 
-import org.onlab.onos.net.provider.Provided;
-
 /**
  * Abstraction of an end-station host on the network, essentially a NIC.
  */
-public interface Host extends Provided {
+public interface Host extends Element {
 
     // MAC, IP(s), optional VLAN ID
 
-    // Location (current, recent locations?
+
+    /**
+     * Returns the most recent host location where the host attaches to the
+     * network edge.
+     *
+     * @return host location
+     */
+    HostLocation location();
+
+    // list of recent locations?
 
 }
diff --git a/net/api/src/main/java/org/onlab/onos/net/HostLocation.java b/net/api/src/main/java/org/onlab/onos/net/HostLocation.java
new file mode 100644
index 0000000..5c124db
--- /dev/null
+++ b/net/api/src/main/java/org/onlab/onos/net/HostLocation.java
@@ -0,0 +1,17 @@
+package org.onlab.onos.net;
+
+/**
+ * Representation of a network edge location where an end-station host is
+ * connected.
+ */
+public interface HostLocation extends ConnectPoint {
+
+    /**
+     * Returns the timestamp when the location was established, given in
+     * milliseconds since start of epoch.
+     *
+     * @return timestamp in milliseconds since start of epoch
+     */
+    long timestamp();
+
+}
diff --git a/net/api/src/main/java/org/onlab/onos/net/Port.java b/net/api/src/main/java/org/onlab/onos/net/Port.java
new file mode 100644
index 0000000..3135b77
--- /dev/null
+++ b/net/api/src/main/java/org/onlab/onos/net/Port.java
@@ -0,0 +1,26 @@
+package org.onlab.onos.net;
+
+/**
+ * Abstraction of a network port.
+ */
+public interface Port {
+
+    // Notion of port state: enabled, disabled, blocked
+
+    /**
+     * Returns the port number.
+     *
+     * @return port number
+     */
+    PortNumber number();
+
+    /**
+     * Returns the identifier of the network element to which this port belongs.
+     *
+     * @return parent network element
+     */
+    Element parent();
+
+    // set of port attributes
+
+}
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);
+
 }