Adding model abstractions to help flesh-out the concepts.
diff --git a/net/api/src/main/java/org/onlab/onos/net/host/HostService.java b/net/api/src/main/java/org/onlab/onos/net/host/HostService.java
new file mode 100644
index 0000000..ed94522
--- /dev/null
+++ b/net/api/src/main/java/org/onlab/onos/net/host/HostService.java
@@ -0,0 +1,67 @@
+package org.onlab.onos.net.host;
+
+import org.onlab.onos.net.ConnectPoint;
+import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.ElementId;
+import org.onlab.onos.net.Host;
+
+import java.util.Set;
+
+/**
+ * Service for interacting with the inventory of end-station hosts.
+ */
+public interface HostService {
+
+ /**
+ * Returns a collection of all end-station hosts.
+ *
+ * @return collection of hosts
+ */
+ Iterable<Host> getHosts();
+
+ /**
+ * Returns the host with the specified identifier.
+ *
+ * @param hostId host identifier
+ * @return host or null if one with the given identifier is not known
+ */
+ Host getHost(ElementId hostId); // TODO: change to HostId
+
+ // TODO: determine which ones make sense or which we care to support
+ // Set<Host> getHostsByVlan(VlanId vlan);
+ // Set<Host> getHostsByMac(MacAddress mac);
+ // Set<Host> getHostsByIp(IpAddress ip);
+
+ /**
+ * Returns the set of hosts whose most recent location is the specified
+ * connection point.
+ *
+ * @param connectPoint connection point
+ * @return set of hosts connected to the connection point
+ */
+ Set<Host> getConnectedHosts(ConnectPoint connectPoint);
+
+ /**
+ * Returns the set of hosts whose most recent location is the specified
+ * infrastructure device.
+ *
+ * @param deviceId device identifier
+ * @return set of hosts connected to the device
+ */
+ Set<Host> getConnectedHosts(DeviceId deviceId);
+
+ /**
+ * Adds the specified host listener.
+ *
+ * @param listener host listener
+ */
+ void addListener(HostListener listener);
+
+ /**
+ * Removes the specified host listener.
+ *
+ * @param listener host listener
+ */
+ void removeListener(HostListener listener);
+
+}