YMS broker and Notification handler

Change-Id: Ic3659b2c2ad26ea2db1f03725b4883f19db2cc41
diff --git a/apps/yms/api/src/main/java/org/onosproject/yms/ysr/YangModuleIdentifier.java b/apps/yms/api/src/main/java/org/onosproject/yms/ysr/YangModuleIdentifier.java
new file mode 100644
index 0000000..6b02720
--- /dev/null
+++ b/apps/yms/api/src/main/java/org/onosproject/yms/ysr/YangModuleIdentifier.java
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2016-present 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.yms.ysr;
+
+/**
+ * Abstraction of an entity which provides YANG module identifiers.
+ * Reference RFC 7895
+ * YANG library provides information about all the YANG modules
+ * used by a network management server
+ */
+public interface YangModuleIdentifier {
+    /**
+     * retrieves the name of the YANG module.
+     *
+     * @return the name of the YANG module
+     */
+    String getModuleName();
+
+    /**
+     * Retrieves revision of the YANG module.
+     *
+     * Reference RFC 7895
+     * Each YANG module and submodule within the library has a
+     * revision.  This is derived from the most recent revision statement
+     * within the module or submodule.  If no such revision statement
+     * exists, the module's or submodule's revision is the zero-length
+     * string.
+     *
+     * @return revision of the YANG module
+     */
+    String getRevision();
+}