diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupService.java b/core/api/src/main/java/org/onosproject/net/group/GroupService.java
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+++ b/core/api/src/main/java/org/onosproject/net/group/GroupService.java
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+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.net.group;
+
+import org.onosproject.core.ApplicationId;
+import org.onosproject.net.Device;
+import org.onosproject.net.DeviceId;
+
+/**
+ * Service for create/update/delete "group" in the devices.
+ * Flow entries can point to a "group" defined in the devices that enables
+ * to represent additional methods of forwarding like load-balancing or
+ * failover among different group of ports or multicast to all ports
+ * specified in a group.
+ * "group" can also be used for grouping common actions of different flows,
+ * so that in some scenarios only one group entry required to be modified
+ * for all the referencing flow entries instead of modifying all of them
+ *
+ * This implements semantics of a distributed authoritative group store
+ * where the master copy of the groups lies with the controller and
+ * the devices hold only the 'cached' copy.
+ */
+public interface GroupService {
+
+    /**
+     * Create a group in the specified device with the provided buckets.
+     * This API provides an option for application to associate a cookie
+     * while creating a group, so that applications can look-up the
+     * groups based on the cookies. These Groups will be retained by
+     * the core system and re-applied if any groups found missing in the
+     * device when it reconnects. This API would immediately return after
+     * submitting the request locally or to a remote Master controller
+     * instance. As a response to this API invocation, GROUP_ADDED or
+     * GROUP_ADD_FAILED notifications would be provided along with cookie
+     * depending on the result of the operation on the device in the
+     * data plane. The caller may also use "getGroup" API to get the
+     * Group object created as part of this request.
+     *
+     * @param groupDesc group creation parameters
+     *
+     */
+    void addGroup(GroupDescription groupDesc);
+
+    /**
+     * Return a group object associated to an application cookie.
+     *
+     * NOTE1: The presence of group object in the system does not
+     * guarantee that the "group" is actually created in device.
+     * GROUP_ADDED notification would confirm the creation of
+     * this group in data plane
+     *
+     * @param deviceId device identifier
+     * @param appCookie application cookie to be used for lookup
+     *
+     * @return group associated with the application cookie or
+     *               NULL if Group is not found for the provided cookie
+     */
+    Group getGroup(DeviceId deviceId, GroupKey appCookie);
+
+    /**
+     * Append buckets to existing group. The caller can optionally
+     * associate a new cookie during this updation. GROUP_UPDATED or
+     * GROUP_UPDATE_FAILED notifications would be provided along with
+     * cookie depending on the result of the operation on the device
+     *
+     * @param deviceId device identifier
+     * @param oldCookie cookie to be used to retrieve the existing group
+     * @param buckets immutable list of group bucket to be added
+     * @param newCookie immutable cookie to be used post update operation
+     * @param appId Application Id
+     */
+    void addBucketsToGroup(DeviceId deviceId,
+                           GroupKey oldCookie,
+                           GroupBuckets buckets,
+                           GroupKey newCookie,
+                           ApplicationId appId);
+
+    /**
+     * Remove buckets from existing group. The caller can optionally
+     * associate a new cookie during this updation. GROUP_UPDATED or
+     * GROUP_UPDATE_FAILED notifications would be provided along with
+     * cookie depending on the result of the operation on the device
+     *
+     * @param deviceId device identifier
+     * @param oldCookie cookie to be used to retrieve the existing group
+     * @param buckets immutable list of group bucket to be removed
+     * @param newCookie immutable cookie to be used post update operation
+     * @param appId Application Id
+     */
+    void removeBucketsFromGroup(Device deviceId,
+                                GroupKey oldCookie,
+                                GroupBuckets buckets,
+                                GroupKey newCookie,
+                                ApplicationId appId);
+
+    /**
+     * Delete a group associated to an application cookie.
+     * GROUP_DELETED or GROUP_DELETE_FAILED notifications would be
+     * provided along with cookie depending on the result of the
+     * operation on the device
+     *
+     * @param deviceId device identifier
+     * @param appCookie application cookie to be used for lookup
+     * @param appId Application Id
+     */
+    void removeGroup(Device deviceId, GroupKey appCookie, ApplicationId appId);
+
+    /**
+     * Retrieve all groups created by an application in the specified device
+     * as seen by current controller instance.
+     *
+     * @param deviceId device identifier
+     * @param appId application id
+     *
+     * @return collection of immutable group objects created by the application
+     */
+    Iterable<Group> getGroups(Device deviceId, ApplicationId appId);
+
+    /**
+     * Adds the specified group listener.
+     *
+     * @param listener group listener
+     */
+    void addListener(GroupListener listener);
+
+    /**
+     * Removes the specified group listener.
+     *
+     * @param listener group listener
+     */
+    void removeListener(GroupListener listener);
+}