[ONOS-5695] notification defect fix

Change-Id: I5f2a7e857975244061e969dd248878b3f2ecda44
diff --git a/apps/yms/app/src/main/java/org/onosproject/yms/app/yob/YobConstants.java b/apps/yms/app/src/main/java/org/onosproject/yms/app/yob/YobConstants.java
index cf2638e..7c38e6c 100644
--- a/apps/yms/app/src/main/java/org/onosproject/yms/app/yob/YobConstants.java
+++ b/apps/yms/app/src/main/java/org/onosproject/yms/app/yob/YobConstants.java
@@ -40,6 +40,9 @@
     static final String JAVA_LANG = "java.lang";
     static final String LEAF_IDENTIFIER = "LeafIdentifier";
     static final String SELECT_LEAF = "selectLeaf";
+    static final String EVENT_SUBJECT = "EventSubject";
+    static final String EVENT = "Event";
+    static final String TYPE = "Type";
 
     //Error strings
     static final String E_NO_HANDLE_FOR_YDT = "No handler for YDT node";