diff --git a/src/main/java/net/onrc/onos/core/intent/ShortestPathIntent.java b/src/main/java/net/onrc/onos/core/intent/ShortestPathIntent.java
index f62ec38..94f3f36 100644
--- a/src/main/java/net/onrc/onos/core/intent/ShortestPathIntent.java
+++ b/src/main/java/net/onrc/onos/core/intent/ShortestPathIntent.java
@@ -21,6 +21,17 @@
     protected ShortestPathIntent() {
     }
 
+    /**
+     * Constructor for ShortestPathIntent.
+     *
+     * @param id Intent ID
+     * @param srcSwitch Source Switch DPID
+     * @param srcPort Source Port
+     * @param srcMac Source Host MAC Address
+     * @param dstSwitch Destination Switch DPID
+     * @param dstPort Destination Port
+     * @param dstMac Destination Host MAC Address
+     */
     public ShortestPathIntent(String id,
                               long srcSwitch, long srcPort, long srcMac,
                               long dstSwitch, long dstPort, long dstMac) {
@@ -33,26 +44,56 @@
         dstMacAddress = dstMac;
     }
 
+    /**
+     * Gets the source Switch DPID.
+     *
+     * @return Source Switch DPID
+     */
     public long getSrcSwitchDpid() {
         return srcSwitchDpid;
     }
 
+    /**
+     * Gets the source Port.
+     *
+     * @return Source Port
+     */
     public long getSrcPortNumber() {
         return srcPortNumber;
     }
 
+    /**
+     * Gets the source Host MAC Address.
+     *
+     * @return Source Host MAC Address
+     */
     public long getSrcMac() {
         return srcMacAddress;
     }
 
+    /**
+     * Gets the destination Switch DPID.
+     *
+     * @return Destination Switch DPID
+     */
     public long getDstSwitchDpid() {
         return dstSwitchDpid;
     }
 
+    /**
+     * Gets the destination Port.
+     *
+     * @return Destination Port
+     */
     public long getDstPortNumber() {
         return dstPortNumber;
     }
 
+    /**
+     * Gets the destination Host MAC Address.
+     *
+     * @return Destination Host MAC Address
+     */
     public long getDstMac() {
         return dstMacAddress;
     }
diff --git a/src/main/java/net/onrc/onos/core/topology/Link.java b/src/main/java/net/onrc/onos/core/topology/Link.java
index 2acf7dc..8715b12 100644
--- a/src/main/java/net/onrc/onos/core/topology/Link.java
+++ b/src/main/java/net/onrc/onos/core/topology/Link.java
@@ -1,42 +1,41 @@
 package net.onrc.onos.core.topology;
 
+// TODO Everything returned by these interfaces must be either Unmodifiable view,
+// immutable object, or a copy of the original "SB" In-memory Topology.
 /**
- * Interface of Link Object exposed to the "NB" read-only Topology.
- * <p/>
- * Everything returned by these interfaces must be either Unmodifiable view,
- * immutable object, or a copy of the original "SB" In-memory Topology.
+ * Interface of Link object in Network Graph topology.
  */
 public interface Link {
     /**
-     * Get the source switch for the link.
+     * Gets the source switch for the link.
      *
      * @return the source switch for the link.
      */
     public Switch getSrcSwitch();
 
     /**
-     * Get the source port for the link.
+     * Gets the source port for the link.
      *
      * @return the source port for the link.
      */
     public Port getSrcPort();
 
     /**
-     * Get the destination switch for the link.
+     * Gets the destination switch for the link.
      *
      * @return the destination switch for the link.
      */
     public Switch getDstSwitch();
 
     /**
-     * Get the destination port for the link.
+     * Gets the destination port for the link.
      *
      * @return the destination port for the link.
      */
     public Port getDstPort();
 
     /**
-     * Get the last seen time for the link.
+     * Gets the last seen time for the link.
      * <p/>
      * TODO: Not implemented yet.
      * TODO: what is the time definition?
@@ -46,7 +45,7 @@
     public long getLastSeenTime();
 
     /**
-     * Get the link cost.
+     * Gets the link cost.
      * <p/>
      * TODO: What is the unit?
      *
@@ -55,7 +54,7 @@
     public int getCost();
 
     /**
-     * Get the link capacity.
+     * Gets the link capacity.
      * <p/>
      * TODO: What is the unit?
      *
diff --git a/src/main/java/net/onrc/onos/core/topology/Port.java b/src/main/java/net/onrc/onos/core/topology/Port.java
index 216d4b8..75aac52 100644
--- a/src/main/java/net/onrc/onos/core/topology/Port.java
+++ b/src/main/java/net/onrc/onos/core/topology/Port.java
@@ -1,26 +1,73 @@
 package net.onrc.onos.core.topology;
 
-
+// TODO Everything returned by these interfaces must be either Unmodifiable view,
+// immutable object, or a copy of the original "SB" In-memory Topology.
 /**
- * Interface of Port Object exposed to the "NB" read-only Topology.
- * <p/>
- * Everything returned by these interfaces must be either Unmodifiable view,
- * immutable object, or a copy of the original "SB" In-memory Topology.
+ * Interface of Port object in Network Graph topology.
  */
 public interface Port {
+
+    /**
+     * Gets the data path ID (dpid) of the switch, which this port is on.
+     *
+     * @return data path ID (dpid)
+     */
     public Long getDpid();
 
+    /**
+     * Gets the port number of this port.
+     *
+     * @return port number
+     */
     public Long getNumber();
 
+    /**
+     * Gets the hardware address of this port.
+     * <p/>
+     * TODO Not implemented yet.
+     * TODO Should return value type be Long?
+     *
+     * @return hardware address
+     */
     public Long getHardwareAddress();
 
+    /**
+     * Description of this port.
+     * <p/>
+     * TODO Not implemented yet.
+     *
+     * @return description of this port
+     */
     public String getDescription();
 
+    /**
+     * Gets the parent switch.
+     *
+     * @return {@link Switch} instance
+     */
     public Switch getSwitch();
 
+    /**
+     * Gets the outgoing link from this port.
+     *
+     * @return {@link Link} if there exist a outgoing link from this,
+     *         {@code null} otherwise.
+     */
     public Link getOutgoingLink();
 
+    /**
+     * Gets the incoming link to this port.
+     *
+     * @return {@link Link} if there exist a incoming link to this, {@code null}
+     *         otherwise.
+     */
     public Link getIncomingLink();
 
+    // XXX Iterable or Collection?
+    /**
+     * Gets all the devices attached to this port.
+     *
+     * @return {@link Device}s attached to this port
+     */
     public Iterable<Device> getDevices();
 }
diff --git a/src/main/java/net/onrc/onos/core/topology/Switch.java b/src/main/java/net/onrc/onos/core/topology/Switch.java
index 690cea8..5f635df 100644
--- a/src/main/java/net/onrc/onos/core/topology/Switch.java
+++ b/src/main/java/net/onrc/onos/core/topology/Switch.java
@@ -2,29 +2,75 @@
 
 import java.util.Collection;
 
+// TOOD Everything returned by these interfaces must be either Unmodifiable view,
+// immutable object, or a copy of the original "SB" In-memory Topology.
 /**
- * Interface of Switch Object exposed to the "NB" read-only Topology.
- * <p/>
- * Everything returned by these interfaces must be either Unmodifiable view,
- * immutable object, or a copy of the original "SB" In-memory Topology.
+ * Interface of Switch object in Network Graph topology.
  */
 public interface Switch {
+
+    /**
+     * Gets the data path ID (dpid) of this switch.
+     *
+     * @return data path ID (dpid)
+     */
     public Long getDpid();
 
+    /**
+     * Gets all the ports on this switch.
+     *
+     * @return Collection of {@link Port} on this switch.
+     */
     public Collection<Port> getPorts();
 
+    /**
+     * Gets a port on switch by port number.
+     *
+     * @param number port number
+     * @return {@link Port} with {@code number} on this switch, or {@code null}
+     *         if this switch did not have a port for specified port number
+     */
     public Port getPort(Long number);
 
     // Graph traversal API
-    // XXX What is the Definition of neighbor? Link exist in both direction or one-way is sufficient to be a neighbor, etc.
+
+    // XXX What is the Definition of neighbor? Link exist in both direction or
+    // one-way is sufficient to be a neighbor, etc.
+    /**
+     * Gets all the neighbor switches.
+     *
+     * @return neighbor switches
+     */
     public Iterable<Switch> getNeighbors();
 
+    /**
+     * Gets all the outgoing links.
+     *
+     * @return outgoing {@link Link}s from this switch.
+     */
     public Iterable<Link> getOutgoingLinks();
 
+    /**
+     * Gets all the incoming links.
+     *
+     * @return outgoing {@link Link}s from this switch.
+     */
     public Iterable<Link> getIncomingLinks();
 
+    /**
+     * Gets outgoing link to specified neighbor switch specified by dpid.
+     *
+     * @param dpid data path ID of neighbor switch.
+     * @return {@link Link} to neighbor switch {@code dpid} or {@code null} if
+     *         link does not exist.
+     */
     public Link getLinkToNeighbor(Long dpid);
 
     // XXX Iterable or Collection?
+    /**
+     * Gets all the devices attached to this switch.
+     *
+     * @return {@link Device}s attached to this switch
+     */
     public Collection<Device> getDevices();
 }