diff --git a/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/utils/UtilConstants.java b/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/utils/UtilConstants.java
index 032493c..d56a2ed 100644
--- a/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/utils/UtilConstants.java
+++ b/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/utils/UtilConstants.java
@@ -647,6 +647,11 @@
     public static final String PUBLIC = "public";
 
     /**
+     * Static attribute for abstract modifier.
+     */
+    public static final String ABSTRACT = "abstract";
+
+    /**
      * Static attribute for protected modifier.
      */
     public static final String PROTECTED = "protected";
@@ -1196,6 +1201,18 @@
             + "leaf/leaf-list for given leafref";
 
     /**
+     * Static attribute for base linker error information.
+     */
+    public static final String BASE_LINKER_ERROR = "YANG file error: Unable to find base "
+            + "identity for given base";
+
+    /**
+     * Static attribute for identityref linker error information.
+     */
+    public static final String IDENTITYREF_LINKER_ERROR = "YANG file error: Unable to find base "
+            + "identity for given base";
+
+    /**
      * Static attribute for reference.
      */
     public static final String REFERENCE = "Reference";