Cleaned up some of the host-related abstractions and filled in more of the host manager implementation.
diff --git a/core/api/src/main/java/org/onlab/onos/net/Host.java b/core/api/src/main/java/org/onlab/onos/net/Host.java
index 17eaf22..d66566d 100644
--- a/core/api/src/main/java/org/onlab/onos/net/Host.java
+++ b/core/api/src/main/java/org/onlab/onos/net/Host.java
@@ -1,12 +1,35 @@
 package org.onlab.onos.net;
 
+import org.onlab.packet.IPv4;
+import org.onlab.packet.MACAddress;
+
+import java.util.Set;
+
 /**
  * Abstraction of an end-station host on the network, essentially a NIC.
  */
 public interface Host extends Element {
 
-    // MAC, IP(s), optional VLAN ID
+    /**
+     * Host identification.
+     *
+     * @return host id
+     */
+    HostId id();
 
+    /**
+     * Returns the host MAC address.
+     *
+     * @return mac address
+     */
+    MACAddress mac();
+
+    /**
+     * Returns set of IP addresses currently bound to the host MAC address.
+     *
+     * @return set of IP addresses; empty if no IP address is bound
+     */
+    Set<IPv4> ipAddresses();
 
     /**
      * Returns the most recent host location where the host attaches to the
@@ -16,6 +39,6 @@
      */
     HostLocation location();
 
-    // list of recent locations?
+    // TODO: explore capturing list of recent locations to aid in mobility
 
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/HostId.java b/core/api/src/main/java/org/onlab/onos/net/HostId.java
index 3e274b3..1c1f2d7 100644
--- a/core/api/src/main/java/org/onlab/onos/net/HostId.java
+++ b/core/api/src/main/java/org/onlab/onos/net/HostId.java
@@ -1,5 +1,7 @@
 package org.onlab.onos.net;
 
+import org.onlab.packet.MACAddress;
+
 import java.net.URI;
 
 /**
@@ -16,6 +18,7 @@
      * Creates a device id using the supplied URI.
      *
      * @param uri device URI
+     * @return host identifier
      */
     public static HostId hostId(URI uri) {
         return new HostId(uri);
@@ -25,9 +28,23 @@
      * Creates a device id using the supplied URI string.
      *
      * @param string device URI string
+     * @return host identifier
      */
     public static HostId hostId(String string) {
         return hostId(URI.create(string));
     }
 
+    /**
+     * Creates a device id using the supplied MAC &amp; VLAN ID.
+     *
+     * @param mac    mac address
+     * @param vlanId vlan identifier
+     * @return host identifier
+     */
+    // FIXME: replace vlanId long with a rich data-type, e.g. VLanId or something like that
+    public static HostId hostId(MACAddress mac, long vlanId) {
+        // FIXME: use more efficient means of encoding
+        return hostId("nic" + ":" + mac + "/" + vlanId);
+    }
+
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/host/HostEvent.java b/core/api/src/main/java/org/onlab/onos/net/host/HostEvent.java
index b06e8b8..2adfb09 100644
--- a/core/api/src/main/java/org/onlab/onos/net/host/HostEvent.java
+++ b/core/api/src/main/java/org/onlab/onos/net/host/HostEvent.java
@@ -23,6 +23,11 @@
         HOST_REMOVED,
 
         /**
+         * Signifies that host data changed, e.g. IP address
+         */
+        HOST_UPDATED,
+
+        /**
          * Signifies that a host location has changed.
          */
         HOST_MOVED
diff --git a/core/api/src/main/java/org/onlab/onos/net/host/HostProviderService.java b/core/api/src/main/java/org/onlab/onos/net/host/HostProviderService.java
index 76c2aad..ed568e8 100644
--- a/core/api/src/main/java/org/onlab/onos/net/host/HostProviderService.java
+++ b/core/api/src/main/java/org/onlab/onos/net/host/HostProviderService.java
@@ -1,5 +1,6 @@
 package org.onlab.onos.net.host;
 
+import org.onlab.onos.net.HostId;
 import org.onlab.onos.net.provider.ProviderService;
 
 /**
@@ -11,15 +12,16 @@
      * Notifies the core when a host has been detected on a network along with
      * information that identifies the hoot location.
      *
+     * @param hostId          id of the host that been detected
      * @param hostDescription description of host and its location
      */
-    void hostDetected(HostDescription hostDescription);
+    void hostDetected(HostId hostId, HostDescription hostDescription);
 
     /**
      * Notifies the core when a host is no longer detected on a network.
      *
-     * @param hostDescription description of host
+     * @param hostId id of the host that vanished
      */
-    void hostVanished(HostDescription hostDescription);
+    void hostVanished(HostId hostId);
 
 }
diff --git a/core/api/src/main/java/org/onlab/onos/net/host/HostService.java b/core/api/src/main/java/org/onlab/onos/net/host/HostService.java
index ed94522..9ffa58a 100644
--- a/core/api/src/main/java/org/onlab/onos/net/host/HostService.java
+++ b/core/api/src/main/java/org/onlab/onos/net/host/HostService.java
@@ -2,8 +2,10 @@
 
 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 org.onlab.onos.net.HostId;
+import org.onlab.packet.IPv4;
+import org.onlab.packet.MACAddress;
 
 import java.util.Set;
 
@@ -13,6 +15,13 @@
 public interface HostService {
 
     /**
+     * Returns the number of end-station hosts known to the system.
+     *
+     * @return number of end-station hosts
+     */
+    public int getHostCount();
+
+    /**
      * Returns a collection of all end-station hosts.
      *
      * @return collection of hosts
@@ -25,12 +34,32 @@
      * @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
+    Host getHost(HostId 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 that belong to the specified VLAN.
+     *
+     * @param vlanId vlan identifier
+     * @return set of hosts in the given vlan id
+     */
+    // FIXME: change long to VLanId
+    Set<Host> getHostsByVlan(long vlanId);
+
+    /**
+     * Returns the set of hosts that have the specified MAC address.
+     *
+     * @param mac mac address
+     * @return set of hosts with the given mac
+     */
+    Set<Host> getHostsByMac(MACAddress mac);
+
+    /**
+     * Returns the set of hosts that have the specified IP address.
+     *
+     * @param ip ip address
+     * @return set of hosts with the given IP
+     */
+    Set<Host> getHostsByIp(IPv4 ip);
 
     /**
      * Returns the set of hosts whose most recent location is the specified
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceManager.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceManager.java
index 17d3aa0..c322b70 100644
--- a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceManager.java
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceManager.java
@@ -51,7 +51,7 @@
     private final AbstractListenerRegistry<DeviceEvent, DeviceListener>
             listenerRegistry = new AbstractListenerRegistry<>();
 
-        private final SimpleDeviceStore store = new SimpleDeviceStore();
+    private final SimpleDeviceStore store = new SimpleDeviceStore();
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected EventDeliveryService eventDispatcher;
@@ -110,21 +110,6 @@
     }
 
     @Override
-    public void addListener(DeviceListener listener) {
-        listenerRegistry.addListener(listener);
-    }
-
-    @Override
-    public void removeListener(DeviceListener listener) {
-        listenerRegistry.removeListener(listener);
-    }
-
-    @Override
-    protected DeviceProviderService createProviderService(DeviceProvider provider) {
-        return new InternalDeviceProviderService(provider);
-    }
-
-    @Override
     public void setRole(DeviceId deviceId, MastershipRole newRole) {
         checkNotNull(deviceId, DEVICE_ID_NULL);
         checkNotNull(newRole, ROLE_NULL);
@@ -149,6 +134,21 @@
         }
     }
 
+    @Override
+    public void addListener(DeviceListener listener) {
+        listenerRegistry.addListener(listener);
+    }
+
+    @Override
+    public void removeListener(DeviceListener listener) {
+        listenerRegistry.removeListener(listener);
+    }
+
+    @Override
+    protected DeviceProviderService createProviderService(DeviceProvider provider) {
+        return new InternalDeviceProviderService(provider);
+    }
+
     // Personalized device provider service issued to the supplied provider.
     private class InternalDeviceProviderService extends AbstractProviderService<DeviceProvider>
             implements DeviceProviderService {
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceStore.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceStore.java
index e219a63..6d16a61 100644
--- a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceStore.java
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleDeviceStore.java
@@ -28,8 +28,7 @@
 import static org.onlab.onos.net.device.DeviceEvent.Type.*;
 
 /**
- * Manages inventory of infrastructure devices using trivial in-memory
- * implementation.
+
  */
 class SimpleDeviceStore {
 
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleHostManager.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleHostManager.java
index 17849b1..05557c5 100644
--- a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleHostManager.java
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleHostManager.java
@@ -8,16 +8,26 @@
 import org.apache.felix.scr.annotations.Service;
 import org.onlab.onos.event.AbstractListenerRegistry;
 import org.onlab.onos.event.EventDeliveryService;
+import org.onlab.onos.net.ConnectPoint;
+import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.Host;
+import org.onlab.onos.net.HostId;
 import org.onlab.onos.net.host.HostDescription;
 import org.onlab.onos.net.host.HostEvent;
 import org.onlab.onos.net.host.HostListener;
 import org.onlab.onos.net.host.HostProvider;
 import org.onlab.onos.net.host.HostProviderRegistry;
 import org.onlab.onos.net.host.HostProviderService;
+import org.onlab.onos.net.host.HostService;
 import org.onlab.onos.net.provider.AbstractProviderRegistry;
 import org.onlab.onos.net.provider.AbstractProviderService;
+import org.onlab.packet.IPv4;
+import org.onlab.packet.MACAddress;
 import org.slf4j.Logger;
 
+import java.util.Set;
+
+import static com.google.common.base.Preconditions.checkNotNull;
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
@@ -27,13 +37,16 @@
 @Service
 public class SimpleHostManager
         extends AbstractProviderRegistry<HostProvider, HostProviderService>
-        implements HostProviderRegistry {
+        implements HostService, HostProviderRegistry {
 
+    public static final String HOST_ID_NULL = "Host ID cannot be null";
     private final Logger log = getLogger(getClass());
 
     private final AbstractListenerRegistry<HostEvent, HostListener>
             listenerRegistry = new AbstractListenerRegistry<>();
 
+    private final SimpleHostStore store = new SimpleHostStore();
+
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     private EventDeliveryService eventDispatcher;
 
@@ -55,8 +68,64 @@
         return new InternalHostProviderService(provider);
     }
 
+    @Override
+    public int getHostCount() {
+        return store.getHostCount();
+    }
+
+    @Override
+    public Iterable<Host> getHosts() {
+        return store.getHosts();
+    }
+
+    @Override
+    public Host getHost(HostId hostId) {
+        checkNotNull(hostId, HOST_ID_NULL);
+        return store.getHost(hostId);
+    }
+
+    @Override
+    public Set<Host> getHostsByVlan(long vlanId) {
+        return store.getHosts(vlanId);
+    }
+
+    @Override
+    public Set<Host> getHostsByMac(MACAddress mac) {
+        checkNotNull(mac, "MAC address cannot be null");
+        return store.getHosts(mac);
+    }
+
+    @Override
+    public Set<Host> getHostsByIp(IPv4 ip) {
+        checkNotNull(ip, "IP address cannot be null");
+        return store.getHosts(ip);
+    }
+
+    @Override
+    public Set<Host> getConnectedHosts(ConnectPoint connectPoint) {
+        checkNotNull(connectPoint, "Connection point cannot be null");
+        return store.getConnectedHosts(connectPoint);
+    }
+
+    @Override
+    public Set<Host> getConnectedHosts(DeviceId deviceId) {
+        checkNotNull(deviceId, "Device ID cannot be null");
+        return store.getConnectedHosts(deviceId);
+    }
+
+    @Override
+    public void addListener(HostListener listener) {
+        listenerRegistry.addListener(listener);
+    }
+
+    @Override
+    public void removeListener(HostListener listener) {
+        listenerRegistry.removeListener(listener);
+    }
+
     // Personalized host provider service issued to the supplied provider.
-    private class InternalHostProviderService extends AbstractProviderService<HostProvider>
+    private class InternalHostProviderService
+            extends AbstractProviderService<HostProvider>
             implements HostProviderService {
 
         InternalHostProviderService(HostProvider provider) {
@@ -64,13 +133,34 @@
         }
 
         @Override
-        public void hostDetected(HostDescription hostDescription) {
-            log.info("Host {} detected", hostDescription);
+        public void hostDetected(HostId hostId, HostDescription hostDescription) {
+            checkNotNull(hostId, HOST_ID_NULL);
+            checkValidity();
+            HostEvent event = store.createOrUpdateHost(provider().id(), hostId,
+                                                       hostDescription);
+            if (event != null) {
+                log.info("Host {} detected", hostId);
+                post(event);
+            }
         }
 
         @Override
-        public void hostVanished(HostDescription hostDescription) {
-            log.info("Host {} vanished", hostDescription);
+        public void hostVanished(HostId hostId) {
+            checkNotNull(hostId, HOST_ID_NULL);
+            checkValidity();
+            HostEvent event = store.removeHost(hostId);
+            if (event != null) {
+                log.info("Host {} vanished", hostId);
+                post(event);
+            }
         }
     }
+
+    // Posts the specified event to the local event dispatcher.
+    private void post(HostEvent event) {
+        if (event != null && eventDispatcher != null) {
+            eventDispatcher.post(event);
+        }
+    }
+
 }
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleHostStore.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleHostStore.java
new file mode 100644
index 0000000..127aad1
--- /dev/null
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleHostStore.java
@@ -0,0 +1,127 @@
+package org.onlab.onos.net.trivial.impl;
+
+import org.onlab.onos.net.ConnectPoint;
+import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.Host;
+import org.onlab.onos.net.HostId;
+import org.onlab.onos.net.host.HostDescription;
+import org.onlab.onos.net.host.HostEvent;
+import org.onlab.onos.net.provider.ProviderId;
+import org.onlab.packet.IPv4;
+import org.onlab.packet.MACAddress;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Manages inventory of end-station hosts using trivial in-memory
+ * implementation.
+ */
+public class SimpleHostStore {
+
+    private final Map<HostId, Host> hosts = new ConcurrentHashMap<>();
+
+    /**
+     * Creates a new host or updates the existing one based on the specified
+     * description.
+     *
+     * @param providerId      provider identification
+     * @param hostId          host identification
+     * @param hostDescription host description data
+     * @return appropriate event or null if no change resulted
+     */
+    HostEvent createOrUpdateHost(ProviderId providerId, HostId hostId,
+                                 HostDescription hostDescription) {
+        return null;
+    }
+
+    /**
+     * Removes the specified host from the inventory.
+     *
+     * @param hostId host identification
+     * @return remove even or null if host was not found
+     */
+    HostEvent removeHost(HostId hostId) {
+        return null;
+    }
+
+    /**
+     * Returns the number of hosts in the store.
+     *
+     * @return host count
+     */
+    int getHostCount() {
+        return hosts.size();
+    }
+
+    /**
+     * Returns a collection of all hosts in the store.
+     *
+     * @return iterable collection of all hosts
+     */
+    Iterable<Host> getHosts() {
+        return null;
+    }
+
+    /**
+     * Returns the host with the specified identifer.
+     *
+     * @param hostId host identification
+     * @return host or null if not found
+     */
+    Host getHost(HostId hostId) {
+        return null;
+    }
+
+    /**
+     * Returns the set of all hosts within the specified VLAN.
+     *
+     * @param vlanId vlan id
+     * @return set of hosts in the vlan
+     */
+    Set<Host> getHosts(long vlanId) {
+        return null;
+    }
+
+    /**
+     * Returns the set of hosts with the specified MAC address.
+     *
+     * @param mac mac address
+     * @return set of hosts with the given mac
+     */
+    Set<Host> getHosts(MACAddress mac) {
+        return null;
+    }
+
+    /**
+     * Returns the set of hosts with the specified IP address.
+     *
+     * @param ip ip address
+     * @return set of hosts with the given IP
+     */
+    Set<Host> getHosts(IPv4 ip) {
+        return null;
+    }
+
+    /**
+     * Returns the set of hosts whose location falls on the given connection point.
+     *
+     * @param connectPoint connection point
+     * @return set of hosts
+     */
+    Set<Host> getConnectedHosts(ConnectPoint connectPoint) {
+        return null;
+    }
+
+    /**
+     * Returns the set of hosts whose location falls on the given device.
+     *
+     * @param deviceId infrastructure device identifier
+     * @return set of hosts
+     */
+    public Set<Host> getConnectedHosts(DeviceId deviceId) {
+        return null;
+    }
+
+}
diff --git a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleLinkManager.java b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleLinkManager.java
index 88d0663..d900c5b 100644
--- a/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleLinkManager.java
+++ b/core/trivial/src/main/java/org/onlab/onos/net/trivial/impl/SimpleLinkManager.java
@@ -66,11 +66,6 @@
     }
 
     @Override
-    protected LinkProviderService createProviderService(LinkProvider provider) {
-        return new InternalLinkProviderService(provider);
-    }
-
-    @Override
     public int getLinkCount() {
         return store.getLinkCount();
     }
@@ -145,6 +140,11 @@
         listenerRegistry.removeListener(listener);
     }
 
+    @Override
+    protected LinkProviderService createProviderService(LinkProvider provider) {
+        return new InternalLinkProviderService(provider);
+    }
+
     // Personalized link provider service issued to the supplied provider.
     private class InternalLinkProviderService extends AbstractProviderService<LinkProvider>
     implements LinkProviderService {