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/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
+
+}