diff --git a/src/main/java/org/onosproject/yangutils/parser/antlrgencode/GeneratedYangListener.java b/src/main/java/org/onosproject/yangutils/parser/antlrgencode/GeneratedYangListener.java
index 236a65b..107c2f1 100644
--- a/src/main/java/org/onosproject/yangutils/parser/antlrgencode/GeneratedYangListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/antlrgencode/GeneratedYangListener.java
@@ -27,7 +27,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * yangfile.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterYangfile(GeneratedYangParser.YangfileContext currentContext);
 
@@ -35,7 +35,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * yangfile.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitYangfile(GeneratedYangParser.YangfileContext currentContext);
 
@@ -43,7 +43,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * moduleStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterModuleStatement(GeneratedYangParser.ModuleStatementContext currentContext);
 
@@ -51,7 +51,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * moduleStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitModuleStatement(GeneratedYangParser.ModuleStatementContext currentContext);
 
@@ -59,7 +59,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * moduleBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterModuleBody(GeneratedYangParser.ModuleBodyContext currentContext);
 
@@ -67,7 +67,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * moduleBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitModuleBody(GeneratedYangParser.ModuleBodyContext currentContext);
 
@@ -75,7 +75,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * moduleHeaderStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterModuleHeaderStatement(GeneratedYangParser.ModuleHeaderStatementContext currentContext);
 
@@ -83,7 +83,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * moduleHeaderStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitModuleHeaderStatement(GeneratedYangParser.ModuleHeaderStatementContext currentContext);
 
@@ -91,7 +91,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * linkageStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterLinkageStatements(GeneratedYangParser.LinkageStatementsContext currentContext);
 
@@ -99,7 +99,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * linkageStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitLinkageStatements(GeneratedYangParser.LinkageStatementsContext currentContext);
 
@@ -107,7 +107,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * metaStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterMetaStatements(GeneratedYangParser.MetaStatementsContext currentContext);
 
@@ -115,7 +115,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * metaStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitMetaStatements(GeneratedYangParser.MetaStatementsContext currentContext);
 
@@ -123,7 +123,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * revisionStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRevisionStatements(GeneratedYangParser.RevisionStatementsContext currentContext);
 
@@ -131,7 +131,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * revisionStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRevisionStatements(GeneratedYangParser.RevisionStatementsContext currentContext);
 
@@ -139,7 +139,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * bodyStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterBodyStatements(GeneratedYangParser.BodyStatementsContext currentContext);
 
@@ -147,7 +147,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * bodyStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitBodyStatements(GeneratedYangParser.BodyStatementsContext currentContext);
 
@@ -155,7 +155,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * yangVersionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterYangVersionStatement(GeneratedYangParser.YangVersionStatementContext currentContext);
 
@@ -163,7 +163,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * yangVersionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitYangVersionStatement(GeneratedYangParser.YangVersionStatementContext currentContext);
 
@@ -171,7 +171,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * namespaceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterNamespaceStatement(GeneratedYangParser.NamespaceStatementContext currentContext);
 
@@ -179,7 +179,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * namespaceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitNamespaceStatement(GeneratedYangParser.NamespaceStatementContext currentContext);
 
@@ -187,7 +187,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * prefixStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterPrefixStatement(GeneratedYangParser.PrefixStatementContext currentContext);
 
@@ -195,7 +195,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * prefixStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitPrefixStatement(GeneratedYangParser.PrefixStatementContext currentContext);
 
@@ -203,7 +203,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * importStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterImportStatement(GeneratedYangParser.ImportStatementContext currentContext);
 
@@ -211,7 +211,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * importStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitImportStatement(GeneratedYangParser.ImportStatementContext currentContext);
 
@@ -219,7 +219,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * importStatementBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterImportStatementBody(GeneratedYangParser.ImportStatementBodyContext currentContext);
 
@@ -227,7 +227,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * importStatementBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitImportStatementBody(GeneratedYangParser.ImportStatementBodyContext currentContext);
 
@@ -235,7 +235,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * revisionDateStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRevisionDateStatement(GeneratedYangParser.RevisionDateStatementContext currentContext);
 
@@ -243,7 +243,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * revisionDateStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRevisionDateStatement(GeneratedYangParser.RevisionDateStatementContext currentContext);
 
@@ -251,7 +251,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * includeStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterIncludeStatement(GeneratedYangParser.IncludeStatementContext currentContext);
 
@@ -259,7 +259,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * includeStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitIncludeStatement(GeneratedYangParser.IncludeStatementContext currentContext);
 
@@ -267,7 +267,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * organizationStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterOrganizationStatement(GeneratedYangParser.OrganizationStatementContext currentContext);
 
@@ -275,7 +275,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * organizationStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitOrganizationStatement(GeneratedYangParser.OrganizationStatementContext currentContext);
 
@@ -283,7 +283,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * contactStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterContactStatement(GeneratedYangParser.ContactStatementContext currentContext);
 
@@ -291,7 +291,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * contactStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitContactStatement(GeneratedYangParser.ContactStatementContext currentContext);
 
@@ -299,7 +299,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * descriptionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterDescriptionStatement(GeneratedYangParser.DescriptionStatementContext currentContext);
 
@@ -307,7 +307,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * descriptionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitDescriptionStatement(GeneratedYangParser.DescriptionStatementContext currentContext);
 
@@ -315,7 +315,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * referenceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterReferenceStatement(GeneratedYangParser.ReferenceStatementContext currentContext);
 
@@ -323,7 +323,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * referenceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitReferenceStatement(GeneratedYangParser.ReferenceStatementContext currentContext);
 
@@ -331,7 +331,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * revisionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRevisionStatement(GeneratedYangParser.RevisionStatementContext currentContext);
 
@@ -339,7 +339,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * revisionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRevisionStatement(GeneratedYangParser.RevisionStatementContext currentContext);
 
@@ -347,7 +347,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * revisionStatementBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRevisionStatementBody(GeneratedYangParser.RevisionStatementBodyContext currentContext);
 
@@ -355,7 +355,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * revisionStatementBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRevisionStatementBody(GeneratedYangParser.RevisionStatementBodyContext currentContext);
 
@@ -363,7 +363,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * subModuleStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterSubModuleStatement(GeneratedYangParser.SubModuleStatementContext currentContext);
 
@@ -371,7 +371,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * subModuleStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitSubModuleStatement(GeneratedYangParser.SubModuleStatementContext currentContext);
 
@@ -379,7 +379,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * submoduleBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterSubmoduleBody(GeneratedYangParser.SubmoduleBodyContext currentContext);
 
@@ -387,7 +387,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * submoduleBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitSubmoduleBody(GeneratedYangParser.SubmoduleBodyContext currentContext);
 
@@ -395,7 +395,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * submoduleHeaderStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterSubmoduleHeaderStatement(GeneratedYangParser.SubmoduleHeaderStatementContext currentContext);
 
@@ -403,7 +403,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * submoduleHeaderStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitSubmoduleHeaderStatement(GeneratedYangParser.SubmoduleHeaderStatementContext currentContext);
 
@@ -411,7 +411,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * belongstoStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterBelongstoStatement(GeneratedYangParser.BelongstoStatementContext currentContext);
 
@@ -419,7 +419,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * belongstoStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitBelongstoStatement(GeneratedYangParser.BelongstoStatementContext currentContext);
 
@@ -427,7 +427,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * belongstoStatementBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterBelongstoStatementBody(GeneratedYangParser.BelongstoStatementBodyContext currentContext);
 
@@ -435,7 +435,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * belongstoStatementBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitBelongstoStatementBody(GeneratedYangParser.BelongstoStatementBodyContext currentContext);
 
@@ -443,7 +443,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * extensionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterExtensionStatement(GeneratedYangParser.ExtensionStatementContext currentContext);
 
@@ -451,7 +451,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * extensionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitExtensionStatement(GeneratedYangParser.ExtensionStatementContext currentContext);
 
@@ -459,7 +459,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * extensionBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterExtensionBody(GeneratedYangParser.ExtensionBodyContext currentContext);
 
@@ -467,7 +467,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * extensionBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitExtensionBody(GeneratedYangParser.ExtensionBodyContext currentContext);
 
@@ -475,7 +475,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * argumentStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterArgumentStatement(GeneratedYangParser.ArgumentStatementContext currentContext);
 
@@ -483,7 +483,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * argumentStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitArgumentStatement(GeneratedYangParser.ArgumentStatementContext currentContext);
 
@@ -491,7 +491,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * argumentBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterArgumentBody(GeneratedYangParser.ArgumentBodyContext currentContext);
 
@@ -499,7 +499,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * argumentBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitArgumentBody(GeneratedYangParser.ArgumentBodyContext currentContext);
 
@@ -507,7 +507,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * yinElementStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterYinElementStatement(GeneratedYangParser.YinElementStatementContext currentContext);
 
@@ -515,7 +515,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * yinElementStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitYinElementStatement(GeneratedYangParser.YinElementStatementContext currentContext);
 
@@ -523,7 +523,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * identityStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterIdentityStatement(GeneratedYangParser.IdentityStatementContext currentContext);
 
@@ -531,7 +531,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * identityStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitIdentityStatement(GeneratedYangParser.IdentityStatementContext currentContext);
 
@@ -539,7 +539,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * identityBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterIdentityBody(GeneratedYangParser.IdentityBodyContext currentContext);
 
@@ -547,7 +547,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * identityBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitIdentityBody(GeneratedYangParser.IdentityBodyContext currentContext);
 
@@ -555,7 +555,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * baseStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterBaseStatement(GeneratedYangParser.BaseStatementContext currentContext);
 
@@ -563,7 +563,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * baseStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitBaseStatement(GeneratedYangParser.BaseStatementContext currentContext);
 
@@ -571,7 +571,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * featureStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterFeatureStatement(GeneratedYangParser.FeatureStatementContext currentContext);
 
@@ -579,7 +579,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * featureStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitFeatureStatement(GeneratedYangParser.FeatureStatementContext currentContext);
 
@@ -587,7 +587,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * featureBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterFeatureBody(GeneratedYangParser.FeatureBodyContext currentContext);
 
@@ -595,7 +595,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * featureBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitFeatureBody(GeneratedYangParser.FeatureBodyContext currentContext);
 
@@ -603,7 +603,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * dataDefStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterDataDefStatement(GeneratedYangParser.DataDefStatementContext currentContext);
 
@@ -611,7 +611,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * dataDefStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitDataDefStatement(GeneratedYangParser.DataDefStatementContext currentContext);
 
@@ -619,7 +619,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * ifFeatureStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterIfFeatureStatement(GeneratedYangParser.IfFeatureStatementContext currentContext);
 
@@ -627,7 +627,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * ifFeatureStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitIfFeatureStatement(GeneratedYangParser.IfFeatureStatementContext currentContext);
 
@@ -635,7 +635,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * unitsStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterUnitsStatement(GeneratedYangParser.UnitsStatementContext currentContext);
 
@@ -643,7 +643,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * unitsStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitUnitsStatement(GeneratedYangParser.UnitsStatementContext currentContext);
 
@@ -651,7 +651,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * typedefStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterTypedefStatement(GeneratedYangParser.TypedefStatementContext currentContext);
 
@@ -659,7 +659,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * typedefStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitTypedefStatement(GeneratedYangParser.TypedefStatementContext currentContext);
 
@@ -667,7 +667,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * typeStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterTypeStatement(GeneratedYangParser.TypeStatementContext currentContext);
 
@@ -675,7 +675,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * typeStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitTypeStatement(GeneratedYangParser.TypeStatementContext currentContext);
 
@@ -683,7 +683,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * typeBodyStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterTypeBodyStatements(GeneratedYangParser.TypeBodyStatementsContext currentContext);
 
@@ -691,7 +691,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * typeBodyStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitTypeBodyStatements(GeneratedYangParser.TypeBodyStatementsContext currentContext);
 
@@ -699,7 +699,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * numericalRestrictions.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterNumericalRestrictions(GeneratedYangParser.NumericalRestrictionsContext currentContext);
 
@@ -707,7 +707,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * numericalRestrictions.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitNumericalRestrictions(GeneratedYangParser.NumericalRestrictionsContext currentContext);
 
@@ -715,7 +715,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * rangeStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRangeStatement(GeneratedYangParser.RangeStatementContext currentContext);
 
@@ -723,7 +723,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * rangeStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRangeStatement(GeneratedYangParser.RangeStatementContext currentContext);
 
@@ -731,7 +731,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * commonStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterCommonStatements(GeneratedYangParser.CommonStatementsContext currentContext);
 
@@ -739,7 +739,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * commonStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitCommonStatements(GeneratedYangParser.CommonStatementsContext currentContext);
 
@@ -747,7 +747,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * stringRestrictions.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterStringRestrictions(GeneratedYangParser.StringRestrictionsContext currentContext);
 
@@ -755,7 +755,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * stringRestrictions.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitStringRestrictions(GeneratedYangParser.StringRestrictionsContext currentContext);
 
@@ -763,7 +763,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * lengthStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterLengthStatement(GeneratedYangParser.LengthStatementContext currentContext);
 
@@ -771,7 +771,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * lengthStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitLengthStatement(GeneratedYangParser.LengthStatementContext currentContext);
 
@@ -779,7 +779,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * patternStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterPatternStatement(GeneratedYangParser.PatternStatementContext currentContext);
 
@@ -787,7 +787,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * patternStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitPatternStatement(GeneratedYangParser.PatternStatementContext currentContext);
 
@@ -795,7 +795,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * defaultStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterDefaultStatement(GeneratedYangParser.DefaultStatementContext currentContext);
 
@@ -803,7 +803,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * defaultStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitDefaultStatement(GeneratedYangParser.DefaultStatementContext currentContext);
 
@@ -811,7 +811,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * enumSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterEnumSpecification(GeneratedYangParser.EnumSpecificationContext currentContext);
 
@@ -819,7 +819,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * enumSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitEnumSpecification(GeneratedYangParser.EnumSpecificationContext currentContext);
 
@@ -827,7 +827,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * enumStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterEnumStatement(GeneratedYangParser.EnumStatementContext currentContext);
 
@@ -835,7 +835,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * enumStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitEnumStatement(GeneratedYangParser.EnumStatementContext currentContext);
 
@@ -843,7 +843,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * enumStatementBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterEnumStatementBody(GeneratedYangParser.EnumStatementBodyContext currentContext);
 
@@ -851,7 +851,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * enumStatementBody.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitEnumStatementBody(GeneratedYangParser.EnumStatementBodyContext currentContext);
 
@@ -859,7 +859,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * leafrefSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterLeafrefSpecification(GeneratedYangParser.LeafrefSpecificationContext currentContext);
 
@@ -867,7 +867,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * leafrefSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitLeafrefSpecification(GeneratedYangParser.LeafrefSpecificationContext currentContext);
 
@@ -875,7 +875,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * pathStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterPathStatement(GeneratedYangParser.PathStatementContext currentContext);
 
@@ -883,7 +883,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * pathStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitPathStatement(GeneratedYangParser.PathStatementContext currentContext);
 
@@ -891,7 +891,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * requireInstanceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRequireInstanceStatement(GeneratedYangParser.RequireInstanceStatementContext currentContext);
 
@@ -899,7 +899,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * requireInstanceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRequireInstanceStatement(GeneratedYangParser.RequireInstanceStatementContext currentContext);
 
@@ -907,7 +907,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * instanceIdentifierSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterInstanceIdentifierSpecification(
             GeneratedYangParser.InstanceIdentifierSpecificationContext currentContext);
@@ -916,7 +916,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * instanceIdentifierSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitInstanceIdentifierSpecification(GeneratedYangParser.InstanceIdentifierSpecificationContext currentContext);
 
@@ -924,7 +924,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * identityrefSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterIdentityrefSpecification(GeneratedYangParser.IdentityrefSpecificationContext currentContext);
 
@@ -932,7 +932,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * identityrefSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitIdentityrefSpecification(GeneratedYangParser.IdentityrefSpecificationContext currentContext);
 
@@ -940,7 +940,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * unionSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterUnionSpecification(GeneratedYangParser.UnionSpecificationContext currentContext);
 
@@ -948,7 +948,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * unionSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitUnionSpecification(GeneratedYangParser.UnionSpecificationContext currentContext);
 
@@ -956,7 +956,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * bitsSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterBitsSpecification(GeneratedYangParser.BitsSpecificationContext currentContext);
 
@@ -964,7 +964,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * bitsSpecification.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitBitsSpecification(GeneratedYangParser.BitsSpecificationContext currentContext);
 
@@ -972,7 +972,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * bitStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterBitStatement(GeneratedYangParser.BitStatementContext currentContext);
 
@@ -980,7 +980,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * bitStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitBitStatement(GeneratedYangParser.BitStatementContext currentContext);
 
@@ -988,7 +988,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * bitBodyStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterBitBodyStatement(GeneratedYangParser.BitBodyStatementContext currentContext);
 
@@ -996,7 +996,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * bitBodyStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitBitBodyStatement(GeneratedYangParser.BitBodyStatementContext currentContext);
 
@@ -1004,7 +1004,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * positionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterPositionStatement(GeneratedYangParser.PositionStatementContext currentContext);
 
@@ -1012,7 +1012,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * positionStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitPositionStatement(GeneratedYangParser.PositionStatementContext currentContext);
 
@@ -1020,7 +1020,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * statusStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterStatusStatement(GeneratedYangParser.StatusStatementContext currentContext);
 
@@ -1028,7 +1028,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * statusStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitStatusStatement(GeneratedYangParser.StatusStatementContext currentContext);
 
@@ -1036,7 +1036,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * configStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterConfigStatement(GeneratedYangParser.ConfigStatementContext currentContext);
 
@@ -1044,7 +1044,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * configStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitConfigStatement(GeneratedYangParser.ConfigStatementContext currentContext);
 
@@ -1052,7 +1052,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * mandatoryStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterMandatoryStatement(GeneratedYangParser.MandatoryStatementContext currentContext);
 
@@ -1060,7 +1060,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * mandatoryStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitMandatoryStatement(GeneratedYangParser.MandatoryStatementContext currentContext);
 
@@ -1068,7 +1068,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * presenceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterPresenceStatement(GeneratedYangParser.PresenceStatementContext currentContext);
 
@@ -1076,7 +1076,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * presenceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitPresenceStatement(GeneratedYangParser.PresenceStatementContext currentContext);
 
@@ -1084,7 +1084,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * orderedByStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterOrderedByStatement(GeneratedYangParser.OrderedByStatementContext currentContext);
 
@@ -1092,7 +1092,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * orderedByStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitOrderedByStatement(GeneratedYangParser.OrderedByStatementContext currentContext);
 
@@ -1100,7 +1100,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * mustStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterMustStatement(GeneratedYangParser.MustStatementContext currentContext);
 
@@ -1108,7 +1108,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * mustStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitMustStatement(GeneratedYangParser.MustStatementContext currentContext);
 
@@ -1116,7 +1116,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * errorMessageStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterErrorMessageStatement(GeneratedYangParser.ErrorMessageStatementContext currentContext);
 
@@ -1124,7 +1124,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * errorMessageStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitErrorMessageStatement(GeneratedYangParser.ErrorMessageStatementContext currentContext);
 
@@ -1132,7 +1132,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * errorAppTagStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterErrorAppTagStatement(GeneratedYangParser.ErrorAppTagStatementContext currentContext);
 
@@ -1140,7 +1140,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * errorAppTagStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitErrorAppTagStatement(GeneratedYangParser.ErrorAppTagStatementContext currentContext);
 
@@ -1148,7 +1148,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * minElementsStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterMinElementsStatement(GeneratedYangParser.MinElementsStatementContext currentContext);
 
@@ -1156,7 +1156,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * minElementsStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitMinElementsStatement(GeneratedYangParser.MinElementsStatementContext currentContext);
 
@@ -1164,7 +1164,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * maxElementsStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterMaxElementsStatement(GeneratedYangParser.MaxElementsStatementContext currentContext);
 
@@ -1172,7 +1172,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * maxElementsStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitMaxElementsStatement(GeneratedYangParser.MaxElementsStatementContext currentContext);
 
@@ -1180,7 +1180,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * maxValueArgument.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterMaxValueArgument(GeneratedYangParser.MaxValueArgumentContext currentContext);
 
@@ -1188,7 +1188,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * maxValueArgument.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitMaxValueArgument(GeneratedYangParser.MaxValueArgumentContext currentContext);
 
@@ -1196,7 +1196,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * valueStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterValueStatement(GeneratedYangParser.ValueStatementContext currentContext);
 
@@ -1204,7 +1204,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * valueStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitValueStatement(GeneratedYangParser.ValueStatementContext currentContext);
 
@@ -1212,7 +1212,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * groupingStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterGroupingStatement(GeneratedYangParser.GroupingStatementContext currentContext);
 
@@ -1220,7 +1220,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * groupingStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitGroupingStatement(GeneratedYangParser.GroupingStatementContext currentContext);
 
@@ -1228,7 +1228,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * containerStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterContainerStatement(GeneratedYangParser.ContainerStatementContext currentContext);
 
@@ -1236,7 +1236,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * containerStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitContainerStatement(GeneratedYangParser.ContainerStatementContext currentContext);
 
@@ -1244,7 +1244,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * leafStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterLeafStatement(GeneratedYangParser.LeafStatementContext currentContext);
 
@@ -1252,7 +1252,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * leafStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitLeafStatement(GeneratedYangParser.LeafStatementContext currentContext);
 
@@ -1260,7 +1260,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * leafListStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterLeafListStatement(GeneratedYangParser.LeafListStatementContext currentContext);
 
@@ -1268,7 +1268,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * leafListStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitLeafListStatement(GeneratedYangParser.LeafListStatementContext currentContext);
 
@@ -1276,7 +1276,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * listStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterListStatement(GeneratedYangParser.ListStatementContext currentContext);
 
@@ -1284,7 +1284,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * listStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitListStatement(GeneratedYangParser.ListStatementContext currentContext);
 
@@ -1292,7 +1292,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * keyStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterKeyStatement(GeneratedYangParser.KeyStatementContext currentContext);
 
@@ -1300,7 +1300,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * keyStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitKeyStatement(GeneratedYangParser.KeyStatementContext currentContext);
 
@@ -1308,7 +1308,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * uniqueStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterUniqueStatement(GeneratedYangParser.UniqueStatementContext currentContext);
 
@@ -1316,7 +1316,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * uniqueStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitUniqueStatement(GeneratedYangParser.UniqueStatementContext currentContext);
 
@@ -1324,7 +1324,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * choiceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterChoiceStatement(GeneratedYangParser.ChoiceStatementContext currentContext);
 
@@ -1332,7 +1332,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * choiceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitChoiceStatement(GeneratedYangParser.ChoiceStatementContext currentContext);
 
@@ -1340,7 +1340,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * shortCaseStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterShortCaseStatement(GeneratedYangParser.ShortCaseStatementContext currentContext);
 
@@ -1348,7 +1348,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * shortCaseStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitShortCaseStatement(GeneratedYangParser.ShortCaseStatementContext currentContext);
 
@@ -1356,7 +1356,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * caseStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterCaseStatement(GeneratedYangParser.CaseStatementContext currentContext);
 
@@ -1364,7 +1364,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * caseStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitCaseStatement(GeneratedYangParser.CaseStatementContext currentContext);
 
@@ -1372,7 +1372,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * usesStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterUsesStatement(GeneratedYangParser.UsesStatementContext currentContext);
 
@@ -1380,7 +1380,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * usesStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitUsesStatement(GeneratedYangParser.UsesStatementContext currentContext);
 
@@ -1388,7 +1388,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * refineStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRefineStatement(GeneratedYangParser.RefineStatementContext currentContext);
 
@@ -1396,7 +1396,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * refineStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRefineStatement(GeneratedYangParser.RefineStatementContext currentContext);
 
@@ -1404,7 +1404,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * refineContainerStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRefineContainerStatements(GeneratedYangParser.RefineContainerStatementsContext currentContext);
 
@@ -1412,7 +1412,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * refineContainerStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRefineContainerStatements(GeneratedYangParser.RefineContainerStatementsContext currentContext);
 
@@ -1420,7 +1420,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * refineLeafStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRefineLeafStatements(GeneratedYangParser.RefineLeafStatementsContext currentContext);
 
@@ -1428,7 +1428,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * refineLeafStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRefineLeafStatements(GeneratedYangParser.RefineLeafStatementsContext currentContext);
 
@@ -1436,7 +1436,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * refineLeafListStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRefineLeafListStatements(GeneratedYangParser.RefineLeafListStatementsContext currentContext);
 
@@ -1444,7 +1444,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * refineLeafListStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRefineLeafListStatements(GeneratedYangParser.RefineLeafListStatementsContext currentContext);
 
@@ -1452,7 +1452,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * refineListStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRefineListStatements(GeneratedYangParser.RefineListStatementsContext currentContext);
 
@@ -1460,7 +1460,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * refineListStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRefineListStatements(GeneratedYangParser.RefineListStatementsContext currentContext);
 
@@ -1468,7 +1468,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * refineChoiceStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRefineChoiceStatements(GeneratedYangParser.RefineChoiceStatementsContext currentContext);
 
@@ -1476,7 +1476,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * refineChoiceStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRefineChoiceStatements(GeneratedYangParser.RefineChoiceStatementsContext currentContext);
 
@@ -1484,7 +1484,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * refineCaseStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRefineCaseStatements(GeneratedYangParser.RefineCaseStatementsContext currentContext);
 
@@ -1492,7 +1492,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * refineCaseStatements.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRefineCaseStatements(GeneratedYangParser.RefineCaseStatementsContext currentContext);
 
@@ -1500,7 +1500,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * usesAugmentStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterUsesAugmentStatement(GeneratedYangParser.UsesAugmentStatementContext currentContext);
 
@@ -1508,7 +1508,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * usesAugmentStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitUsesAugmentStatement(GeneratedYangParser.UsesAugmentStatementContext currentContext);
 
@@ -1516,7 +1516,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * augmentStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterAugmentStatement(GeneratedYangParser.AugmentStatementContext currentContext);
 
@@ -1524,7 +1524,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * augmentStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitAugmentStatement(GeneratedYangParser.AugmentStatementContext currentContext);
 
@@ -1532,7 +1532,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * whenStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterWhenStatement(GeneratedYangParser.WhenStatementContext currentContext);
 
@@ -1540,7 +1540,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * whenStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitWhenStatement(GeneratedYangParser.WhenStatementContext currentContext);
 
@@ -1548,7 +1548,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * rpcStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterRpcStatement(GeneratedYangParser.RpcStatementContext currentContext);
 
@@ -1556,7 +1556,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * rpcStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitRpcStatement(GeneratedYangParser.RpcStatementContext currentContext);
 
@@ -1564,7 +1564,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * inputStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterInputStatement(GeneratedYangParser.InputStatementContext currentContext);
 
@@ -1572,7 +1572,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * inputStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitInputStatement(GeneratedYangParser.InputStatementContext currentContext);
 
@@ -1580,7 +1580,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * outputStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterOutputStatement(GeneratedYangParser.OutputStatementContext currentContext);
 
@@ -1588,7 +1588,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * outputStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitOutputStatement(GeneratedYangParser.OutputStatementContext currentContext);
 
@@ -1596,7 +1596,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * notificationStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterNotificationStatement(GeneratedYangParser.NotificationStatementContext currentContext);
 
@@ -1604,7 +1604,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * notificationStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitNotificationStatement(GeneratedYangParser.NotificationStatementContext currentContext);
 
@@ -1612,7 +1612,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * deviationStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterDeviationStatement(GeneratedYangParser.DeviationStatementContext currentContext);
 
@@ -1620,7 +1620,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * deviationStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitDeviationStatement(GeneratedYangParser.DeviationStatementContext currentContext);
 
@@ -1628,7 +1628,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * deviateNotSupportedStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterDeviateNotSupportedStatement(GeneratedYangParser.DeviateNotSupportedStatementContext currentContext);
 
@@ -1636,7 +1636,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * deviateNotSupportedStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitDeviateNotSupportedStatement(GeneratedYangParser.DeviateNotSupportedStatementContext currentContext);
 
@@ -1644,7 +1644,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * deviateAddStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterDeviateAddStatement(GeneratedYangParser.DeviateAddStatementContext currentContext);
 
@@ -1652,7 +1652,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * deviateAddStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitDeviateAddStatement(GeneratedYangParser.DeviateAddStatementContext currentContext);
 
@@ -1660,7 +1660,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * deviateDeleteStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterDeviateDeleteStatement(GeneratedYangParser.DeviateDeleteStatementContext currentContext);
 
@@ -1668,7 +1668,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * deviateDeleteStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitDeviateDeleteStatement(GeneratedYangParser.DeviateDeleteStatementContext currentContext);
 
@@ -1676,7 +1676,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * deviateReplaceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterDeviateReplaceStatement(GeneratedYangParser.DeviateReplaceStatementContext currentContext);
 
@@ -1684,7 +1684,7 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * deviateReplaceStatement.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitDeviateReplaceStatement(GeneratedYangParser.DeviateReplaceStatementContext currentContext);
 
@@ -1692,7 +1692,7 @@
      * Enter a parse tree produced by GeneratedYangParser for grammar rule
      * string.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void enterString(GeneratedYangParser.StringContext currentContext);
 
@@ -1700,7 +1700,40 @@
      * Exit a parse tree produced by GeneratedYangParser for grammar rule
      * string.
      *
-     * @param currentContext current context in the parsed tree.
+     * @param currentContext current context in the parsed tree
      */
     void exitString(GeneratedYangParser.StringContext currentContext);
+
+    /**
+     * Enter a parse tree produced by GeneratedYangParser for grammar rule
+     * identifier.
+     *
+     * @param currentContext current context in the parsed tree
+     */
+    void enterIdentifier(GeneratedYangParser.IdentifierContext currentContext);
+
+    /**
+     * Exit a parse tree produced by GeneratedYangParser for grammar rule
+     * identifier.
+     *
+     * @param currentContext current context in the parsed tree
+     */
+    void exitIdentifier(GeneratedYangParser.IdentifierContext currentContext);
+
+
+    /**
+     * Enter a parse tree produced by GeneratedYangParser for grammar rule
+     * dateArgumentString.
+     *
+     * @param currentContext current context in the parsed tree
+     */
+    void enterDateArgumentString(GeneratedYangParser.DateArgumentStringContext currentContext);
+
+    /**
+     * Exit a parse tree produced by GeneratedYangParser for grammar rule
+     * dateArgumentString.
+     *
+     * @param currentContext current context in the parsed tree
+     */
+    void exitDateArgumentString(GeneratedYangParser.DateArgumentStringContext currentContext);
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/TreeWalkListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/TreeWalkListener.java
index e615d13..7027dc0 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/TreeWalkListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/TreeWalkListener.java
@@ -1163,6 +1163,26 @@
     }
 
     @Override
+    public void enterIdentifier(GeneratedYangParser.IdentifierContext ctx) {
+        // TODO: implement the method.
+    }
+
+    @Override
+    public void exitIdentifier(GeneratedYangParser.IdentifierContext ctx) {
+        // TODO: implement the method.
+    }
+
+    @Override
+    public void enterDateArgumentString(GeneratedYangParser.DateArgumentStringContext ctx) {
+        // TODO: implement the method.
+    }
+
+    @Override
+    public void exitDateArgumentString(GeneratedYangParser.DateArgumentStringContext ctx) {
+        // TODO: implement the method.
+    }
+
+    @Override
     public void visitTerminal(TerminalNode terminalNode) {
         // TODO: implement the method.
     }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BelongsToListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BelongsToListener.java
index c938190..92b1ee9 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BelongsToListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BelongsToListener.java
@@ -22,6 +22,8 @@
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
@@ -50,7 +52,7 @@
  * submodule_header_statement : yang_version_stmt? belongs_to_stmt
  *                            | belongs_to_stmt yang_version_stmt?
  *                            ;
- * belongs_to_stmt : BELONGS_TO_KEYWORD IDENTIFIER LEFT_CURLY_BRACE belongs_to_stmt_body RIGHT_CURLY_BRACE;
+ * belongs_to_stmt : BELONGS_TO_KEYWORD identifier LEFT_CURLY_BRACE belongs_to_stmt_body RIGHT_CURLY_BRACE;
  * belongs_to_stmt_body : prefix_stmt;
  */
 
@@ -78,11 +80,13 @@
                                              GeneratedYangParser.BelongstoStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, BELONGS_TO_DATA, ctx.IDENTIFIER().getText(),
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, BELONGS_TO_DATA, ctx.identifier().getText(),
                              ENTRY);
 
+        String identifier = getValidIdentifier(ctx.identifier().getText(), BELONGS_TO_DATA, ctx);
+
         YangBelongsTo belongstoNode = new YangBelongsTo();
-        belongstoNode.setBelongsToModuleName(ctx.IDENTIFIER().getText());
+        belongstoNode.setBelongsToModuleName(identifier);
 
         // Push belongsto into the stack.
         listener.getParsedDataStack().push(belongstoNode);
@@ -99,7 +103,7 @@
                                             GeneratedYangParser.BelongstoStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, BELONGS_TO_DATA, ctx.IDENTIFIER().getText(),
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, BELONGS_TO_DATA, ctx.identifier().getText(),
                              EXIT);
 
         Parsable tmpBelongstoNode = listener.getParsedDataStack().peek();
@@ -108,7 +112,7 @@
 
             // Check for stack to be empty.
             checkStackIsNotEmpty(listener, MISSING_HOLDER, BELONGS_TO_DATA,
-                                 ctx.IDENTIFIER().getText(), EXIT);
+                                 ctx.identifier().getText(), EXIT);
 
             Parsable tmpNode = listener.getParsedDataStack().peek();
             switch (tmpNode.getYangConstructType()) {
@@ -119,12 +123,12 @@
             }
             default:
                 throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, BELONGS_TO_DATA,
-                                                                        ctx.IDENTIFIER().getText(),
+                                                                        ctx.identifier().getText(),
                                                                         EXIT));
             }
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, BELONGS_TO_DATA,
-                                                                    ctx.IDENTIFIER().getText(), EXIT));
+                                                                    ctx.identifier().getText(), EXIT));
         }
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BitListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BitListener.java
index b13b3b1..7f15f4e 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BitListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/BitListener.java
@@ -32,7 +32,7 @@
  *                        "}")
  *
  * ANTLR grammar rule
- * bitStatement : BIT_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE bitBodyStatement RIGHT_CURLY_BRACE);
+ * bitStatement : BIT_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE bitBodyStatement RIGHT_CURLY_BRACE);
  *
  * bitBodyStatement : positionStatement? statusStatement? descriptionStatement? referenceStatement?
  *               | positionStatement? statusStatement? referenceStatement? descriptionStatement?
@@ -65,10 +65,12 @@
 import org.onosproject.yangutils.datamodel.YangBits;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.parser.Parsable;
-import static org.onosproject.yangutils.utils.YangConstructType.BIT_DATA;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
+import static org.onosproject.yangutils.utils.YangConstructType.BIT_DATA;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructExtendedListenerErrorMessage;
@@ -102,10 +104,12 @@
                                         GeneratedYangParser.BitStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, BIT_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, BIT_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), BIT_DATA, ctx);
 
         YangBit bitNode = new YangBit();
-        bitNode.setBitName(ctx.IDENTIFIER().getText());
+        bitNode.setBitName(identifier);
         listener.getParsedDataStack().push(bitNode);
     }
 
@@ -120,14 +124,14 @@
                                        GeneratedYangParser.BitStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, BIT_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, BIT_DATA, ctx.identifier().getText(), EXIT);
 
         Parsable tmpBitNode = listener.getParsedDataStack().peek();
         if (tmpBitNode instanceof YangBit) {
             listener.getParsedDataStack().pop();
 
             // Check for stack to be non empty.
-            checkStackIsNotEmpty(listener, MISSING_HOLDER, BIT_DATA, ctx.IDENTIFIER().getText(), EXIT);
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, BIT_DATA, ctx.identifier().getText(), EXIT);
 
             Parsable tmpNode = listener.getParsedDataStack().peek();
             switch (tmpNode.getYangConstructType()) {
@@ -152,20 +156,20 @@
                         yangBits.addBitInfo((YangBit) tmpBitNode);
                     } catch (DataModelException e) {
                         ParserException parserException = new ParserException(constructExtendedListenerErrorMessage(
-                                INVALID_CONTENT, BIT_DATA, ctx.IDENTIFIER().getText(), EXIT, e.getMessage()));
-                        parserException.setLine(ctx.IDENTIFIER().getSymbol().getLine());
-                        parserException.setCharPosition(ctx.IDENTIFIER().getSymbol().getCharPositionInLine());
+                                INVALID_CONTENT, BIT_DATA, ctx.identifier().getText(), EXIT, e.getMessage()));
+                        parserException.setLine(ctx.getStart().getLine());
+                        parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
                         throw parserException;
                     }
                     break;
                 }
                 default:
                     throw new ParserException(
-                            constructListenerErrorMessage(INVALID_HOLDER, BIT_DATA, ctx.IDENTIFIER().getText(), EXIT));
+                            constructListenerErrorMessage(INVALID_HOLDER, BIT_DATA, ctx.identifier().getText(), EXIT));
             }
         } else {
             throw new ParserException(
-                    constructListenerErrorMessage(MISSING_CURRENT_HOLDER, BIT_DATA, ctx.IDENTIFIER().getText(), EXIT));
+                    constructListenerErrorMessage(MISSING_CURRENT_HOLDER, BIT_DATA, ctx.identifier().getText(), EXIT));
         }
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
index 1f23449..6cdf77b 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
@@ -25,6 +25,9 @@
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerCollisionDetector.detectCollidingChildUtil;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
@@ -34,7 +37,6 @@
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.UNHANDLED_PARSED_DATA;
-import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.validateCardinality;
 import static org.onosproject.yangutils.utils.YangConstructType.CONFIG_DATA;
@@ -66,7 +68,7 @@
  *                         "}")
  *
  * ANTLR grammar rule
- *  containerStatement : CONTAINER_KEYWORD IDENTIFIER
+ *  containerStatement : CONTAINER_KEYWORD identifier
  *                   (STMTEND | LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | mustStatement |
  *                   presenceStatement | configStatement | statusStatement | descriptionStatement |
  *                   referenceStatement | typedefStatement | groupingStatement
@@ -96,19 +98,20 @@
             GeneratedYangParser.ContainerStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, CONTAINER_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, CONTAINER_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), CONTAINER_DATA, ctx);
 
         // Validate sub statement cardinality.
         validateSubStatementsCardinality(ctx);
 
         // Check for identifier collision
-        int line = ctx.IDENTIFIER().getSymbol().getLine();
-        int charPositionInLine = ctx.IDENTIFIER().getSymbol().getCharPositionInLine();
-        String identifierName = ctx.IDENTIFIER().getText();
-        detectCollidingChildUtil(listener, line, charPositionInLine, identifierName, CONTAINER_DATA);
+        int line = ctx.getStart().getLine();
+        int charPositionInLine = ctx.getStart().getCharPositionInLine();
+        detectCollidingChildUtil(listener, line, charPositionInLine, identifier, CONTAINER_DATA);
 
         YangContainer container = new YangContainer();
-        container.setName(ctx.IDENTIFIER().getText());
+        container.setName(identifier);
 
         /*
          * If "config" is not specified, the default is the same as the parent
@@ -127,12 +130,12 @@
                 curNode.addChild(container);
             } catch (DataModelException e) {
                 throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
-                        CONTAINER_DATA, ctx.IDENTIFIER().getText(), ENTRY, e.getMessage()));
+                                CONTAINER_DATA, ctx.identifier().getText(), ENTRY, e.getMessage()));
             }
             listener.getParsedDataStack().push(container);
         } else {
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, CONTAINER_DATA,
-                    ctx.IDENTIFIER().getText(), ENTRY));
+                    ctx.identifier().getText(), ENTRY));
         }
     }
 
@@ -147,7 +150,7 @@
             GeneratedYangParser.ContainerStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, CONTAINER_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, CONTAINER_DATA, ctx.identifier().getText(), EXIT);
 
         if (listener.getParsedDataStack().peek() instanceof YangContainer) {
             YangContainer yangContainer = (YangContainer) listener.getParsedDataStack().peek();
@@ -155,12 +158,12 @@
                 yangContainer.validateDataOnExit();
             } catch (DataModelException e) {
                 throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
-                        CONTAINER_DATA, ctx.IDENTIFIER().getText(), EXIT, e.getMessage()));
+                        CONTAINER_DATA, ctx.identifier().getText(), EXIT, e.getMessage()));
             }
             listener.getParsedDataStack().pop();
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, CONTAINER_DATA,
-                    ctx.IDENTIFIER().getText(), EXIT));
+                            ctx.identifier().getText(), EXIT));
         }
     }
 
@@ -171,11 +174,11 @@
      */
     private static void validateSubStatementsCardinality(GeneratedYangParser.ContainerStatementContext ctx) {
 
-        validateCardinality(ctx.presenceStatement(), PRESENCE_DATA, CONTAINER_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.configStatement(), CONFIG_DATA, CONTAINER_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, CONTAINER_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, CONTAINER_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.statusStatement(), STATUS_DATA, CONTAINER_DATA, ctx.IDENTIFIER().getText());
+        validateCardinality(ctx.presenceStatement(), PRESENCE_DATA, CONTAINER_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.configStatement(), CONFIG_DATA, CONTAINER_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, CONTAINER_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, CONTAINER_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.statusStatement(), STATUS_DATA, CONTAINER_DATA, ctx.identifier().getText());
         // TODO when, grouping, typedef.
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java
index bd120ad..f34bd30 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java
@@ -23,6 +23,8 @@
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
@@ -49,7 +51,7 @@
  * ANTLR grammar rule
  * linkage_stmts : (import_stmt
  *               | include_stmt)*;
- * import_stmt : IMPORT_KEYWORD IDENTIFIER LEFT_CURLY_BRACE import_stmt_body
+ * import_stmt : IMPORT_KEYWORD identifier LEFT_CURLY_BRACE import_stmt_body
  *               RIGHT_CURLY_BRACE;
  * import_stmt_body : prefix_stmt revision_date_stmt?;
  */
@@ -76,10 +78,12 @@
     public static void processImportEntry(TreeWalkListener listener, GeneratedYangParser.ImportStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), IMPORT_DATA, ctx);
 
         YangImport importNode = new YangImport();
-        importNode.setModuleName(ctx.IDENTIFIER().getText());
+        importNode.setModuleName(identifier);
 
         // Push import node to the stack.
         listener.getParsedDataStack().push(importNode);
@@ -95,14 +99,14 @@
     public static void processImportExit(TreeWalkListener listener, GeneratedYangParser.ImportStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.identifier().getText(), EXIT);
 
         Parsable tmpImportNode = listener.getParsedDataStack().peek();
         if (tmpImportNode instanceof YangImport) {
             listener.getParsedDataStack().pop();
 
             // Check for stack to be non empty.
-            checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.IDENTIFIER().getText(),
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.identifier().getText(),
                                  EXIT);
 
             Parsable tmpNode = listener.getParsedDataStack().peek();
@@ -119,12 +123,12 @@
             }
             default:
                 throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, IMPORT_DATA,
-                                                                        ctx.IDENTIFIER().getText(),
+                                                                        ctx.identifier().getText(),
                                                                         EXIT));
             }
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, IMPORT_DATA,
-                                                                    ctx.IDENTIFIER().getText(), EXIT));
+                                                                    ctx.identifier().getText(), EXIT));
         }
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/IncludeListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/IncludeListener.java
index 6e28ada..b9325da 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/IncludeListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/IncludeListener.java
@@ -23,6 +23,8 @@
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
@@ -49,7 +51,7 @@
  * ANTLR grammar rule
  * linkage_stmts : (import_stmt
  *               | include_stmt)*;
- * include_stmt : INCLUDE_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE
+ * include_stmt : INCLUDE_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE
  *                revision_date_stmt? RIGHT_CURLY_BRACE);
  */
 
@@ -75,11 +77,13 @@
     public static void processIncludeEntry(TreeWalkListener listener, GeneratedYangParser.IncludeStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, INCLUDE_DATA, ctx.IDENTIFIER().getText(),
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, INCLUDE_DATA, ctx.identifier().getText(),
                              ENTRY);
 
+        String identifier = getValidIdentifier(ctx.identifier().getText(), INCLUDE_DATA, ctx);
+
         YangInclude includeNode = new YangInclude();
-        includeNode.setSubModuleName(ctx.IDENTIFIER().getText());
+        includeNode.setSubModuleName(identifier);
 
         listener.getParsedDataStack().push(includeNode);
     }
@@ -94,14 +98,14 @@
     public static void processIncludeExit(TreeWalkListener listener, GeneratedYangParser.IncludeStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, INCLUDE_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, INCLUDE_DATA, ctx.identifier().getText(), EXIT);
 
         Parsable tmpIncludeNode = listener.getParsedDataStack().peek();
         if (tmpIncludeNode instanceof YangInclude) {
             listener.getParsedDataStack().pop();
 
             // Check for stack to be non empty.
-            checkStackIsNotEmpty(listener, MISSING_HOLDER, INCLUDE_DATA, ctx.IDENTIFIER().getText(),
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, INCLUDE_DATA, ctx.identifier().getText(),
                                  EXIT);
 
             Parsable tmpNode = listener.getParsedDataStack().peek();
@@ -118,12 +122,12 @@
             }
             default:
                 throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, INCLUDE_DATA,
-                                                                        ctx.IDENTIFIER().getText(),
+                                                                        ctx.identifier().getText(),
                                                                         EXIT));
             }
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, INCLUDE_DATA,
-                                                                    ctx.IDENTIFIER().getText(), EXIT));
+                                                                    ctx.identifier().getText(), EXIT));
         }
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListener.java
index 896e8ec..0a867cc 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListener.java
@@ -22,6 +22,8 @@
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerCollisionDetector.detectCollidingChildUtil;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
@@ -64,7 +66,7 @@
  *                         "}"
  *
  * ANTLR grammar rule
- *  leafListStatement : LEAF_LIST_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement |
+ *  leafListStatement : LEAF_LIST_KEYWORD identifier LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement |
  *  typeStatement | unitsStatement | mustStatement | configStatement | minElementsStatement | maxElementsStatement |
  *  orderedByStatement | statusStatement | descriptionStatement | referenceStatement)* RIGHT_CURLY_BRACE;
  */
@@ -92,19 +94,20 @@
             GeneratedYangParser.LeafListStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_LIST_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_LIST_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), LEAF_LIST_DATA, ctx);
 
         // Validate sub statement cardinality.
         validateSubStatementsCardinality(ctx);
 
         // Check for identifier collision
-        int line = ctx.IDENTIFIER().getSymbol().getLine();
-        int charPositionInLine = ctx.IDENTIFIER().getSymbol().getCharPositionInLine();
-        String identifierName = ctx.IDENTIFIER().getText();
-        detectCollidingChildUtil(listener, line, charPositionInLine, identifierName, LEAF_LIST_DATA);
+        int line = ctx.getStart().getLine();
+        int charPositionInLine = ctx.getStart().getCharPositionInLine();
+        detectCollidingChildUtil(listener, line, charPositionInLine, identifier, LEAF_LIST_DATA);
 
         YangLeafList leafList = new YangLeafList();
-        leafList.setLeafName(ctx.IDENTIFIER().getText());
+        leafList.setLeafName(identifier);
 
         Parsable tmpData = listener.getParsedDataStack().peek();
         YangLeavesHolder leaves;
@@ -114,7 +117,7 @@
             leaves.addLeafList(leafList);
         } else {
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, LEAF_LIST_DATA,
-                    ctx.IDENTIFIER().getText(), ENTRY));
+                            ctx.identifier().getText(), ENTRY));
         }
         listener.getParsedDataStack().push(leafList);
     }
@@ -130,31 +133,31 @@
             GeneratedYangParser.LeafListStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_LIST_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_LIST_DATA, ctx.identifier().getText(), EXIT);
 
         if (listener.getParsedDataStack().peek() instanceof YangLeafList) {
             listener.getParsedDataStack().pop();
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, LEAF_LIST_DATA,
-                    ctx.IDENTIFIER().getText(), EXIT));
+                    ctx.identifier().getText(), EXIT));
         }
     }
 
     /**
      * Validates the cardinality of leaf-list sub-statements as per grammar.
      *
-     * @param ctx context object of the grammar rule.
+     * @param ctx context object of the grammar rule
      */
     private static void validateSubStatementsCardinality(GeneratedYangParser.LeafListStatementContext ctx) {
 
-        validateCardinalityEqualsOne(ctx.typeStatement(), TYPE_DATA, LEAF_LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.unitsStatement(), UNITS_DATA, LEAF_LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.configStatement(), CONFIG_DATA, LEAF_LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.maxElementsStatement(), MAX_ELEMENT_DATA, LEAF_LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.minElementsStatement(), MIN_ELEMENT_DATA, LEAF_LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, LEAF_LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, LEAF_LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.statusStatement(), STATUS_DATA, LEAF_LIST_DATA, ctx.IDENTIFIER().getText());
+        validateCardinalityEqualsOne(ctx.typeStatement(), TYPE_DATA, LEAF_LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.unitsStatement(), UNITS_DATA, LEAF_LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.configStatement(), CONFIG_DATA, LEAF_LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.maxElementsStatement(), MAX_ELEMENT_DATA, LEAF_LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.minElementsStatement(), MIN_ELEMENT_DATA, LEAF_LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, LEAF_LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, LEAF_LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.statusStatement(), STATUS_DATA, LEAF_LIST_DATA, ctx.identifier().getText());
         //TODO ordered by
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListener.java
index 226f621..4573764 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LeafListener.java
@@ -26,6 +26,8 @@
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerCollisionDetector.detectCollidingChildUtil;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
@@ -66,7 +68,7 @@
  *                         "}"
  *
  * ANTLR grammar rule
- *  leafStatement : LEAF_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | typeStatement |
+ *  leafStatement : LEAF_KEYWORD identifier LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | typeStatement |
  *  unitsStatement | mustStatement | defaultStatement | configStatement | mandatoryStatement | statusStatement  |
  *  descriptionStatement | referenceStatement)* RIGHT_CURLY_BRACE;
  */
@@ -94,19 +96,20 @@
             GeneratedYangParser.LeafStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), LEAF_DATA, ctx);
 
         // Validate sub statement cardinality.
         validateSubStatementsCardinality(ctx);
 
         // Check for identifier collision
-        int line = ctx.IDENTIFIER().getSymbol().getLine();
-        int charPositionInLine = ctx.IDENTIFIER().getSymbol().getCharPositionInLine();
-        String identifierName = ctx.IDENTIFIER().getText();
-        detectCollidingChildUtil(listener, line, charPositionInLine, identifierName, LEAF_DATA);
+        int line = ctx.getStart().getLine();
+        int charPositionInLine = ctx.getStart().getCharPositionInLine();
+        detectCollidingChildUtil(listener, line, charPositionInLine, identifier, LEAF_DATA);
 
         YangLeaf leaf = new YangLeaf();
-        leaf.setLeafName(ctx.IDENTIFIER().getText());
+        leaf.setLeafName(identifier);
 
         Parsable tmpData = listener.getParsedDataStack().peek();
         YangLeavesHolder leaves;
@@ -116,7 +119,7 @@
             leaves.addLeaf(leaf);
         } else {
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, LEAF_DATA,
-                    ctx.IDENTIFIER().getText(), ENTRY));
+                    ctx.identifier().getText(), ENTRY));
         }
 
         listener.getParsedDataStack().push(leaf);
@@ -126,37 +129,37 @@
      * It is called when parser exits from grammar rule (leaf), performs
      * validation and updates the data model tree.
      *
-     * @param listener listener's object.
-     * @param ctx context object of the grammar rule.
+     * @param listener listener's object
+     * @param ctx context object of the grammar rule
      */
     public static void processLeafExit(TreeWalkListener listener,
             GeneratedYangParser.LeafStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, LEAF_DATA, ctx.identifier().getText(), EXIT);
 
         if (listener.getParsedDataStack().peek() instanceof YangLeaf) {
             listener.getParsedDataStack().pop();
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, LEAF_DATA,
-                    ctx.IDENTIFIER().getText(), EXIT));
+                            ctx.identifier().getText(), EXIT));
         }
     }
 
     /**
      * Validates the cardinality of leaf sub-statements as per grammar.
      *
-     * @param ctx context object of the grammar rule.
+     * @param ctx context object of the grammar rule
      */
     private static void validateSubStatementsCardinality(GeneratedYangParser.LeafStatementContext ctx) {
 
-        validateCardinalityEqualsOne(ctx.typeStatement(), TYPE_DATA, LEAF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.unitsStatement(), UNITS_DATA, LEAF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.configStatement(), CONFIG_DATA, LEAF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.mandatoryStatement(), MANDATORY_DATA, LEAF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, LEAF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, LEAF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.statusStatement(), STATUS_DATA, LEAF_DATA, ctx.IDENTIFIER().getText());
+        validateCardinalityEqualsOne(ctx.typeStatement(), TYPE_DATA, LEAF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.unitsStatement(), UNITS_DATA, LEAF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.configStatement(), CONFIG_DATA, LEAF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.mandatoryStatement(), MANDATORY_DATA, LEAF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, LEAF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, LEAF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.statusStatement(), STATUS_DATA, LEAF_DATA, ctx.identifier().getText());
         //TODO when.
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
index d71186e..50f2fd5 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
@@ -27,6 +27,7 @@
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
 import org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation;
 
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerCollisionDetector.detectCollidingChildUtil;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
@@ -74,7 +75,7 @@
  *                         "}"
  *
  * ANTLR grammar rule
- *  listStatement : LIST_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | mustStatement |
+ *  listStatement : LIST_KEYWORD identifier LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | mustStatement |
  *  keyStatement | uniqueStatement | configStatement | minElementsStatement | maxElementsStatement |
  *  orderedByStatement | statusStatement | descriptionStatement | referenceStatement | typedefStatement |
  *  groupingStatement| dataDefStatement)* RIGHT_CURLY_BRACE;
@@ -104,19 +105,20 @@
 
         YangNode curNode;
 
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, LIST_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, LIST_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), LIST_DATA, ctx);
 
         // Validate sub statement cardinality.
         validateSubStatementsCardinality(ctx);
 
         // Check for identifier collision
-        int line = ctx.IDENTIFIER().getSymbol().getLine();
-        int charPositionInLine = ctx.IDENTIFIER().getSymbol().getCharPositionInLine();
-        String identifierName = ctx.IDENTIFIER().getText();
-        detectCollidingChildUtil(listener, line, charPositionInLine, identifierName, LIST_DATA);
+        int line = ctx.getStart().getLine();
+        int charPositionInLine = ctx.getStart().getCharPositionInLine();
+        detectCollidingChildUtil(listener, line, charPositionInLine, identifier, LIST_DATA);
 
         YangList yangList = new YangList();
-        yangList.setName(ctx.IDENTIFIER().getText());
+        yangList.setName(identifier);
 
         /*
          * If "config" is not specified, the default is the same as the parent
@@ -135,12 +137,12 @@
                 curNode.addChild(yangList);
             } catch (DataModelException e) {
                 throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
-                        LIST_DATA, ctx.IDENTIFIER().getText(), ENTRY, e.getMessage()));
+                        LIST_DATA, ctx.identifier().getText(), ENTRY, e.getMessage()));
             }
             listener.getParsedDataStack().push(yangList);
         } else {
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, LIST_DATA,
-                    ctx.IDENTIFIER().getText(), ENTRY));
+                            ctx.identifier().getText(), ENTRY));
         }
     }
 
@@ -154,7 +156,7 @@
     public static void processListExit(TreeWalkListener listener,
             GeneratedYangParser.ListStatementContext ctx) {
 
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, LIST_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, LIST_DATA, ctx.identifier().getText(), EXIT);
 
         if (listener.getParsedDataStack().peek() instanceof YangList) {
             YangList yangList = (YangList) listener.getParsedDataStack().peek();
@@ -162,12 +164,12 @@
                 yangList.validateDataOnExit();
             } catch (DataModelException e) {
                 throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
-                        LIST_DATA, ctx.IDENTIFIER().getText(), EXIT, e.getMessage()));
+                        LIST_DATA, ctx.identifier().getText(), EXIT, e.getMessage()));
             }
             listener.getParsedDataStack().pop();
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, LIST_DATA,
-                    ctx.IDENTIFIER().getText(), EXIT));
+                            ctx.identifier().getText(), EXIT));
         }
     }
 
@@ -178,14 +180,14 @@
      */
     private static void validateSubStatementsCardinality(GeneratedYangParser.ListStatementContext ctx) {
 
-        validateCardinality(ctx.keyStatement(), KEY_DATA, LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.configStatement(), CONFIG_DATA, LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.maxElementsStatement(), MAX_ELEMENT_DATA, LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.minElementsStatement(), MIN_ELEMENT_DATA, LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.statusStatement(), STATUS_DATA, LIST_DATA, ctx.IDENTIFIER().getText());
-        validateCardinalityNonNull(ctx.dataDefStatement(), DATA_DEF_DATA, LIST_DATA, ctx.IDENTIFIER().getText());
+        validateCardinality(ctx.keyStatement(), KEY_DATA, LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.configStatement(), CONFIG_DATA, LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.maxElementsStatement(), MAX_ELEMENT_DATA, LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.minElementsStatement(), MIN_ELEMENT_DATA, LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, LIST_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.statusStatement(), STATUS_DATA, LIST_DATA, ctx.identifier().getText());
+        validateCardinalityNonNull(ctx.dataDefStatement(), DATA_DEF_DATA, LIST_DATA, ctx.identifier().getText());
         //TODO when, typedef, grouping, unique
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListener.java
index f4f6ef5..bc8ee02 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListener.java
@@ -20,6 +20,8 @@
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
@@ -45,7 +47,7 @@
  *                       "}" optsep
  *
  * ANTLR grammar rule
- * module_stmt : MODULE_KEYWORD IDENTIFIER LEFT_CURLY_BRACE module_body* RIGHT_CURLY_BRACE;
+ * module_stmt : MODULE_KEYWORD identifier LEFT_CURLY_BRACE module_body* RIGHT_CURLY_BRACE;
  */
 
 /**
@@ -70,10 +72,12 @@
     public static void processModuleEntry(TreeWalkListener listener, GeneratedYangParser.ModuleStatementContext ctx) {
 
         // Check if stack is empty.
-        checkStackIsEmpty(listener, INVALID_HOLDER, MODULE_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsEmpty(listener, INVALID_HOLDER, MODULE_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), MODULE_DATA, ctx);
 
         YangModule yangModule = new YangModule();
-        yangModule.setName(ctx.IDENTIFIER().getText());
+        yangModule.setName(identifier);
 
         if (ctx.moduleBody(0).moduleHeaderStatement().yangVersionStatement() == null) {
             yangModule.setVersion((byte) 1);
@@ -92,11 +96,11 @@
     public static void processModuleExit(TreeWalkListener listener, GeneratedYangParser.ModuleStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, MODULE_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, MODULE_DATA, ctx.identifier().getText(), EXIT);
 
         if (!(listener.getParsedDataStack().peek() instanceof YangModule)) {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, MODULE_DATA,
-                                                                    ctx.IDENTIFIER().getText(), EXIT));
+                                                                    ctx.identifier().getText(), EXIT));
         }
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PositionListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PositionListener.java
index 43e600b..a4a094b 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PositionListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PositionListener.java
@@ -30,7 +30,7 @@
  * zero-integer-value  = 1*DIGIT
  *
  * ANTLR grammar rule
- * positionStatement : POSITION_KEYWORD INTEGER STMTEND;
+ * positionStatement : POSITION_KEYWORD string STMTEND;
  */
 
 import org.onosproject.yangutils.datamodel.YangBit;
@@ -44,6 +44,7 @@
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.removeQuotesAndHandleConcat;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.utils.YangConstructType.POSITION_DATA;
 
@@ -73,25 +74,27 @@
             GeneratedYangParser.PositionStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, POSITION_DATA, ctx.INTEGER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, POSITION_DATA, ctx.string().getText(), ENTRY);
+
+        String position = removeQuotesAndHandleConcat(ctx.string().getText());
 
         // Obtain the node of the stack.
         Parsable tmpNode = listener.getParsedDataStack().peek();
         switch (tmpNode.getYangConstructType()) {
             case BIT_DATA: {
                 YangBit bitNode = (YangBit) tmpNode;
-                if (!isBitPositionValid(listener, ctx)) {
+                if (!isBitPositionValid(listener, ctx, position)) {
                     ParserException parserException = new ParserException(errMsg);
-                    parserException.setLine(ctx.INTEGER().getSymbol().getLine());
-                    parserException.setCharPosition(ctx.INTEGER().getSymbol().getCharPositionInLine());
+                    parserException.setLine(ctx.getStart().getLine());
+                    parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
                     throw parserException;
                 }
-                bitNode.setPosition(Integer.valueOf(ctx.INTEGER().getText()));
+                bitNode.setPosition(Integer.valueOf(position));
                 break;
             }
             default:
                 throw new ParserException(
-                        constructListenerErrorMessage(INVALID_HOLDER, POSITION_DATA, ctx.INTEGER().getText(), ENTRY));
+                        constructListenerErrorMessage(INVALID_HOLDER, POSITION_DATA, ctx.string().getText(), ENTRY));
         }
     }
 
@@ -103,13 +106,13 @@
      * @return validation result
      */
     private static boolean isBitPositionValid(TreeWalkListener listener,
-            GeneratedYangParser.PositionStatementContext ctx) {
+            GeneratedYangParser.PositionStatementContext ctx, String position) {
         Parsable bitNode = listener.getParsedDataStack().pop();
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, POSITION_DATA, ctx.INTEGER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, POSITION_DATA, ctx.string().getText(), ENTRY);
 
-        if (Integer.valueOf(ctx.INTEGER().getText()) < 0) {
+        if (Integer.valueOf(position) < 0) {
             errMsg = "YANG file error: Negative value of position is invalid.";
             listener.getParsedDataStack().push(bitNode);
             return false;
@@ -120,7 +123,7 @@
             case BITS_DATA: {
                 YangBits yangBits = (YangBits) tmpNode;
                 for (YangBit curBit : yangBits.getBitSet()) {
-                    if (Integer.valueOf(ctx.INTEGER().getText()) == curBit.getPosition()) {
+                    if (Integer.valueOf(position) == curBit.getPosition()) {
                         errMsg = "YANG file error: Duplicate value of position is invalid.";
                         listener.getParsedDataStack().push(bitNode);
                         return false;
@@ -132,7 +135,7 @@
             default:
                 listener.getParsedDataStack().push(bitNode);
                 throw new ParserException(
-                        constructListenerErrorMessage(INVALID_HOLDER, POSITION_DATA, ctx.INTEGER().getText(), ENTRY));
+                        constructListenerErrorMessage(INVALID_HOLDER, POSITION_DATA, ctx.string().getText(), ENTRY));
         }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListener.java
index e59cda0..1fbe6dd 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListener.java
@@ -24,6 +24,7 @@
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
 
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.utils.YangConstructType.PREFIX_DATA;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
@@ -51,7 +52,7 @@
  *                         | prefix_stmt namespace_stmt yang_version_stmt?
  *                         | prefix_stmt yang_version_stmt? namespace_stmt
  *                         ;
- * prefix_stmt : PREFIX_KEYWORD IDENTIFIER STMTEND;
+ * prefix_stmt : PREFIX_KEYWORD identifier STMTEND;
  */
 
 /**
@@ -76,29 +77,31 @@
     public static void processPrefixEntry(TreeWalkListener listener, GeneratedYangParser.PrefixStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, PREFIX_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, PREFIX_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), PREFIX_DATA, ctx);
 
         // Obtain the node of the stack.
         Parsable tmpNode = listener.getParsedDataStack().peek();
         switch (tmpNode.getYangConstructType()) {
         case MODULE_DATA: {
             YangModule module = (YangModule) tmpNode;
-            module.setPrefix(ctx.IDENTIFIER().getText());
+            module.setPrefix(identifier);
             break;
         }
         case IMPORT_DATA: {
             YangImport importNode = (YangImport) tmpNode;
-            importNode.setPrefixId(ctx.IDENTIFIER().getText());
+            importNode.setPrefixId(identifier);
             break;
         }
         case BELONGS_TO_DATA: {
             YangBelongsTo belongstoNode = (YangBelongsTo) tmpNode;
-            belongstoNode.setPrefix(ctx.IDENTIFIER().getText());
+            belongstoNode.setPrefix(identifier);
             break;
         }
         default:
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, PREFIX_DATA,
-                                                                    ctx.IDENTIFIER().getText(), ENTRY));
+                                                                    ctx.identifier().getText(), ENTRY));
         }
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListener.java
index 03f1cb1..f5c4993 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListener.java
@@ -16,10 +16,6 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
-import java.text.ParseException;
-import java.text.SimpleDateFormat;
-import java.util.Date;
-
 import org.onosproject.yangutils.datamodel.YangImport;
 import org.onosproject.yangutils.datamodel.YangInclude;
 import org.onosproject.yangutils.parser.Parsable;
@@ -27,6 +23,8 @@
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
 
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.removeQuotesAndHandleConcat;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.isDateValid;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
@@ -86,13 +84,14 @@
             GeneratedYangParser.RevisionDateStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATE_DATA, ctx.DATE_ARG().getText(),
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATE_DATA, ctx.dateArgumentString().getText(),
                 ENTRY);
 
-        if (!isDateValid(ctx.DATE_ARG().getText())) {
+        String date = removeQuotesAndHandleConcat(ctx.dateArgumentString().getText());
+        if (!isDateValid(date)) {
             ParserException parserException = new ParserException("YANG file error: Input date is not correct");
-            parserException.setLine(ctx.DATE_ARG().getSymbol().getLine());
-            parserException.setCharPosition(ctx.DATE_ARG().getSymbol().getCharPositionInLine());
+            parserException.setLine(ctx.getStart().getLine());
+            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
             throw parserException;
         }
 
@@ -101,42 +100,17 @@
         switch (tmpNode.getYangConstructType()) {
             case IMPORT_DATA: {
                 YangImport importNode = (YangImport) tmpNode;
-                importNode.setRevision(ctx.DATE_ARG().getText());
+                importNode.setRevision(date);
                 break;
             }
             case INCLUDE_DATA: {
                 YangInclude includeNode = (YangInclude) tmpNode;
-                includeNode.setRevision(ctx.DATE_ARG().getText());
+                includeNode.setRevision(date);
                 break;
             }
             default:
                 throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, REVISION_DATE_DATA,
-                        ctx.DATE_ARG().getText(), ENTRY));
+                        ctx.dateArgumentString().getText(), ENTRY));
         }
     }
-
-    /**
-     * Validates the revision date.
-     *
-     * @param dateToValidate input revision date
-     * @return validation result, true for success, false for failure
-     */
-    private static boolean isDateValid(String dateToValidate) {
-
-        if (dateToValidate == null) {
-            return false;
-        }
-
-        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
-        sdf.setLenient(false);
-
-        try {
-            //if not valid, it will throw ParseException
-            Date date = sdf.parse(dateToValidate);
-            System.out.println(date);
-        } catch (ParseException e) {
-            return false;
-        }
-        return true;
-    }
 }
\ No newline at end of file
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionListener.java
index 32675cd..dd29457 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RevisionListener.java
@@ -24,6 +24,8 @@
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
 
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.removeQuotesAndHandleConcat;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.isDateValid;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
@@ -33,10 +35,6 @@
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 
-import java.text.ParseException;
-import java.text.SimpleDateFormat;
-import java.util.Date;
-
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
  *
@@ -88,7 +86,7 @@
                                             GeneratedYangParser.RevisionStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATA, ctx.DATE_ARG().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATA, ctx.dateArgumentString().getText(), ENTRY);
 
         // Validate for reverse chronological order of revision & for revision
         // value.
@@ -97,15 +95,16 @@
             // TODO to be implemented.
         }
 
-        if (!isDateValid(ctx.DATE_ARG().getText())) {
+        String date = removeQuotesAndHandleConcat(ctx.dateArgumentString().getText());
+        if (!isDateValid(date)) {
             ParserException parserException = new ParserException("YANG file error: Input date is not correct");
-            parserException.setLine(ctx.DATE_ARG().getSymbol().getLine());
-            parserException.setCharPosition(ctx.DATE_ARG().getSymbol().getCharPositionInLine());
+            parserException.setLine(ctx.getStart().getLine());
+            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
             throw parserException;
         }
 
         YangRevision revisionNode = new YangRevision();
-        revisionNode.setRevDate(ctx.DATE_ARG().getText());
+        revisionNode.setRevDate(date);
 
         listener.getParsedDataStack().push(revisionNode);
     }
@@ -121,14 +120,14 @@
             ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATA, ctx.DATE_ARG().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATA, ctx.dateArgumentString().getText(), EXIT);
 
         Parsable tmpRevisionNode = listener.getParsedDataStack().peek();
         if (tmpRevisionNode instanceof YangRevision) {
             listener.getParsedDataStack().pop();
 
             // Check for stack to be non empty.
-            checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATA, ctx.DATE_ARG().getText(),
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATA, ctx.dateArgumentString().getText(),
                                  EXIT);
 
             Parsable tmpNode = listener.getParsedDataStack().peek();
@@ -145,12 +144,12 @@
             }
             default:
                 throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, REVISION_DATA,
-                                                                        ctx.DATE_ARG().getText(),
+                                                                        ctx.dateArgumentString().getText(),
                                                                         EXIT));
             }
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, REVISION_DATA,
-                                                                    ctx.DATE_ARG().getText(), EXIT));
+                                                                    ctx.dateArgumentString().getText(), EXIT));
         }
     }
 
@@ -166,29 +165,4 @@
         // TODO to be implemented
         return true;
     }
-
-    /**
-     * Validates the revision date.
-     *
-     * @param dateToValidate input revision date
-     * @return validation result, true for success, false for failure
-     */
-    private static boolean isDateValid(String dateToValidate) {
-
-        if (dateToValidate == null) {
-            return false;
-        }
-
-        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
-        sdf.setLenient(false);
-
-        try {
-            //if not valid, it will throw ParseException
-            Date date = sdf.parse(dateToValidate);
-            System.out.println(date);
-        } catch (ParseException e) {
-            return false;
-        }
-        return true;
-    }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java
index 4f8a64e..080767a 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/SubModuleListener.java
@@ -20,6 +20,8 @@
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
@@ -45,7 +47,7 @@
  *                             "}" optsep
  *
  * ANTLR grammar rule
- * submodule_stmt : SUBMODULE_KEYWORD IDENTIFIER LEFT_CURLY_BRACE submodule_body* RIGHT_CURLY_BRACE;
+ * submodule_stmt : SUBMODULE_KEYWORD identifier LEFT_CURLY_BRACE submodule_body* RIGHT_CURLY_BRACE;
  * submodule_body : submodule_header_statement linkage_stmts meta_stmts revision_stmts body_stmts;
  */
 
@@ -72,11 +74,13 @@
                                              GeneratedYangParser.SubModuleStatementContext ctx) {
 
         // Check if stack is empty.
-        checkStackIsEmpty(listener, INVALID_HOLDER, SUB_MODULE_DATA, ctx.IDENTIFIER().getText(),
+        checkStackIsEmpty(listener, INVALID_HOLDER, SUB_MODULE_DATA, ctx.identifier().getText(),
                           ENTRY);
 
+        String identifier = getValidIdentifier(ctx.identifier().getText(), SUB_MODULE_DATA, ctx);
+
         YangSubModule yangSubModule = new YangSubModule();
-        yangSubModule.setName(ctx.IDENTIFIER().getText());
+        yangSubModule.setName(identifier);
 
         if (ctx.submoduleBody(0).submoduleHeaderStatement().yangVersionStatement() == null) {
             yangSubModule.setVersion((byte) 1);
@@ -96,12 +100,12 @@
                                             GeneratedYangParser.SubModuleStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, SUB_MODULE_DATA, ctx.IDENTIFIER().getText(),
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, SUB_MODULE_DATA, ctx.identifier().getText(),
                              EXIT);
 
         if (!(listener.getParsedDataStack().peek() instanceof YangSubModule)) {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, SUB_MODULE_DATA,
-                                                                    ctx.IDENTIFIER().getText(), EXIT));
+                                                                    ctx.identifier().getText(), EXIT));
         }
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java
index d2af63e..4622ccf 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java
@@ -42,7 +42,7 @@
  *                         "}"
  *
  * ANTLR grammar rule
- * typedefStatement : TYPEDEF_KEYWORD IDENTIFIER LEFT_CURLY_BRACE
+ * typedefStatement : TYPEDEF_KEYWORD identifier LEFT_CURLY_BRACE
  *                (typeStatement | unitsStatement | defaultStatement | statusStatement
  *                | descriptionStatement | referenceStatement)* RIGHT_CURLY_BRACE;
  */
@@ -62,6 +62,7 @@
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
 
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructExtendedListenerErrorMessage;
@@ -105,7 +106,9 @@
             GeneratedYangParser.TypedefStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, TYPEDEF_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, TYPEDEF_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), TYPEDEF_DATA, ctx);
 
         // Validate sub statement cardinality.
         validateSubStatementsCardinality(ctx);
@@ -116,7 +119,7 @@
          */
         YangType<YangDerivedType> derivedType = new YangType<YangDerivedType>();
         derivedType.setDataType(YangDataTypes.DERIVED);
-        derivedType.setDataTypeName(ctx.IDENTIFIER().getText());
+        derivedType.setDataTypeName(identifier);
 
         YangTypeDef typeDefNode = new YangTypeDef();
         typeDefNode.setDerivedType(derivedType);
@@ -133,12 +136,12 @@
                 curNode.addChild(typeDefNode);
             } catch (DataModelException e) {
                 throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
-                        TYPEDEF_DATA, ctx.IDENTIFIER().getText(), ENTRY, e.getMessage()));
+                        TYPEDEF_DATA, ctx.identifier().getText(), ENTRY, e.getMessage()));
             }
             listener.getParsedDataStack().push(typeDefNode);
         } else {
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER,
-                    TYPEDEF_DATA, ctx.IDENTIFIER().getText(), ENTRY));
+                    TYPEDEF_DATA, ctx.identifier().getText(), ENTRY));
         }
     }
 
@@ -153,7 +156,7 @@
             GeneratedYangParser.TypedefStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, TYPEDEF_DATA, ctx.IDENTIFIER().getText(), EXIT);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, TYPEDEF_DATA, ctx.identifier().getText(), EXIT);
 
         if (listener.getParsedDataStack().peek() instanceof YangTypeDef) {
             YangTypeDef typeDefNode = (YangTypeDef) listener.getParsedDataStack().peek();
@@ -161,13 +164,13 @@
                 typeDefNode.validateDataOnExit();
             } catch (DataModelException e) {
                 throw new ParserException(constructListenerErrorMessage(INVALID_CONTENT, TYPEDEF_DATA,
-                        ctx.IDENTIFIER().getText(), EXIT));
+                        ctx.identifier().getText(), EXIT));
             }
 
             listener.getParsedDataStack().pop();
         } else {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, TYPEDEF_DATA,
-                    ctx.IDENTIFIER().getText(), EXIT));
+                    ctx.identifier().getText(), EXIT));
         }
     }
 
@@ -178,11 +181,11 @@
      */
     private static void validateSubStatementsCardinality(GeneratedYangParser.TypedefStatementContext ctx) {
 
-        validateCardinality(ctx.unitsStatement(), UNITS_DATA, TYPEDEF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.defaultStatement(), DEFAULT_DATA, TYPEDEF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinalityEqualsOne(ctx.typeStatement(), TYPE_DATA, TYPEDEF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, TYPEDEF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, TYPEDEF_DATA, ctx.IDENTIFIER().getText());
-        validateCardinality(ctx.statusStatement(), STATUS_DATA, TYPEDEF_DATA, ctx.IDENTIFIER().getText());
+        validateCardinality(ctx.unitsStatement(), UNITS_DATA, TYPEDEF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.defaultStatement(), DEFAULT_DATA, TYPEDEF_DATA, ctx.identifier().getText());
+        validateCardinalityEqualsOne(ctx.typeStatement(), TYPE_DATA, TYPEDEF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.descriptionStatement(), DESCRIPTION_DATA, TYPEDEF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.referenceStatement(), REFERENCE_DATA, TYPEDEF_DATA, ctx.identifier().getText());
+        validateCardinality(ctx.statusStatement(), STATUS_DATA, TYPEDEF_DATA, ctx.identifier().getText());
     }
 }
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
index 9b9a388..f8d5361 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
@@ -23,6 +23,7 @@
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
 
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.removeQuotesAndHandleConcat;
 import static org.onosproject.yangutils.utils.YangConstructType.VERSION_DATA;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
@@ -59,7 +60,7 @@
  * submodule_header_statement : yang_version_stmt? belongs_to_stmt
  *                            | belongs_to_stmt yang_version_stmt?
  *                            ;
- * yang_version_stmt :   YANG_VERSION_KEYWORD INTEGER STMTEND;
+ * yang_version_stmt :   YANG_VERSION_KEYWORD string STMTEND;
  */
 
 /**
@@ -85,13 +86,13 @@
                                            GeneratedYangParser.YangVersionStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, VERSION_DATA, ctx.INTEGER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, VERSION_DATA, ctx.string().getText(), ENTRY);
 
-        Integer version = Integer.valueOf(ctx.INTEGER().getText());
-        if (!isVersionValid(version)) {
+        String version = removeQuotesAndHandleConcat(ctx.string().getText());
+        if (!isVersionValid(Integer.valueOf(version))) {
             ParserException parserException = new ParserException("YANG file error: Input version not supported");
-            parserException.setLine(ctx.INTEGER().getSymbol().getLine());
-            parserException.setCharPosition(ctx.INTEGER().getSymbol().getCharPositionInLine());
+            parserException.setLine(ctx.getStart().getLine());
+            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
             throw parserException;
         }
 
@@ -110,7 +111,7 @@
         }
         default:
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, VERSION_DATA,
-                                                                    ctx.INTEGER().getText(), ENTRY));
+                                                                    ctx.string().getText(), ENTRY));
         }
     }
 
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerUtil.java b/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerUtil.java
new file mode 100644
index 0000000..41b2418
--- /dev/null
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerUtil.java
@@ -0,0 +1,112 @@
+/*
+ * Copyright 2016 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.yangutils.parser.impl.parserutils;
+
+import org.antlr.v4.runtime.ParserRuleContext;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.regex.Pattern;
+import org.onosproject.yangutils.utils.YangConstructType;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+
+/**
+ * It's a utility for listener.
+ */
+public final class ListenerUtil {
+    private static final Pattern IDENTIFIER_PATTERN = Pattern.compile("[a-zA-Z_][a-zA-Z0-9_.-]*");
+    private static final String PLUS = "+";
+    private static final int IDENTIFIER_LENGTH = 64;
+
+    /**
+     * Creates a new listener util.
+     */
+    private ListenerUtil() {
+    }
+
+    /**
+     * Removes doubles quotes and concatenates if string has plus symbol.
+     *
+     * @param yangStringData string from yang file
+     * @return concatenated string after removing double quotes
+     */
+    public static String removeQuotesAndHandleConcat(String yangStringData) {
+
+        yangStringData = yangStringData.replace("\"", "");
+        String[] tmpData = yangStringData.split(Pattern.quote(PLUS));
+        StringBuilder builder = new StringBuilder();
+        for (String yangString : tmpData) {
+            builder.append(yangString);
+        }
+        return builder.toString();
+    }
+
+    /**
+     * Validates identifier and returns concatenated string if string contains plus symbol.
+     *
+     * @param identifier string from yang file
+     * @param yangConstruct yang construct for creating error message
+     * @param ctx yang construct's context to get the line number and character position
+     * @return concatenated string after removing double quotes
+     */
+    public static String getValidIdentifier(String identifier, YangConstructType yangConstruct, ParserRuleContext ctx) {
+
+        String identifierString = removeQuotesAndHandleConcat(identifier);
+        ParserException parserException;
+
+        if (identifierString.length() > IDENTIFIER_LENGTH) {
+            parserException = new ParserException("YANG file error : " +
+                    YangConstructType.getYangConstructType(yangConstruct) + " name " + identifierString + " is " +
+                    "greater than 64 characters.");
+        } else if (!IDENTIFIER_PATTERN.matcher(identifierString).matches()) {
+            parserException = new ParserException("YANG file error : " +
+                    YangConstructType.getYangConstructType(yangConstruct) + " name " + identifierString + " is not " +
+                    "valid.");
+        } else {
+            return identifierString;
+        }
+
+        parserException.setLine(ctx.getStart().getLine());
+        parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+        throw parserException;
+    }
+
+    /**
+     * Validates the revision date.
+     *
+     * @param dateToValidate input revision date
+     * @return validation result, true for success, false for failure
+     */
+    public static boolean isDateValid(String dateToValidate) {
+
+        if (dateToValidate == null || !dateToValidate.matches("[0-9]{4}-[0-9]{2}-[0-9]{2}")) {
+            return false;
+        }
+
+        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
+        sdf.setLenient(false);
+
+        try {
+            //if not valid, it will throw ParseException
+            sdf.parse(dateToValidate);
+        } catch (ParseException e) {
+            return false;
+        }
+
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/src/main/resources/GeneratedYang.g4 b/src/main/resources/GeneratedYang.g4
index b3272bc..9614b21 100644
--- a/src/main/resources/GeneratedYang.g4
+++ b/src/main/resources/GeneratedYang.g4
@@ -40,7 +40,7 @@
      *                       "}" optsep
      */
 
-    moduleStatement : MODULE_KEYWORD IDENTIFIER LEFT_CURLY_BRACE moduleBody* RIGHT_CURLY_BRACE;
+    moduleStatement : MODULE_KEYWORD identifier LEFT_CURLY_BRACE moduleBody* RIGHT_CURLY_BRACE;
 
     moduleBody : moduleHeaderStatement linkageStatements metaStatements revisionStatements bodyStatements;
 
@@ -135,7 +135,7 @@
      *                       optsep stmtend
      */
 
-    yangVersionStatement :   YANG_VERSION_KEYWORD INTEGER STMTEND;
+    yangVersionStatement :   YANG_VERSION_KEYWORD string STMTEND;
 
 
     /**
@@ -148,7 +148,7 @@
      * prefix-stmt         = prefix-keyword sep prefix-arg-str
      *                       optsep stmtend
      */
-    prefixStatement : PREFIX_KEYWORD IDENTIFIER STMTEND;
+    prefixStatement : PREFIX_KEYWORD identifier STMTEND;
 
     /**
      * import-stmt         = import-keyword sep identifier-arg-str optsep
@@ -157,12 +157,12 @@
      *                           [revision-date-stmt stmtsep]
      *                        "}"
      */
-    importStatement : IMPORT_KEYWORD IDENTIFIER LEFT_CURLY_BRACE importStatementBody RIGHT_CURLY_BRACE;
+    importStatement : IMPORT_KEYWORD identifier LEFT_CURLY_BRACE importStatementBody RIGHT_CURLY_BRACE;
 
     importStatementBody : prefixStatement revisionDateStatement?;
 
     // revision-date-stmt = revision-date-keyword sep revision-date stmtend
-    revisionDateStatement : REVISION_DATE_KEYWORD DATE_ARG STMTEND;
+    revisionDateStatement : REVISION_DATE_KEYWORD dateArgumentString STMTEND;
 
     /**
      * include-stmt        = include-keyword sep identifier-arg-str optsep
@@ -171,7 +171,7 @@
      *                                  [revision-date-stmt stmtsep]
      *                            "}")
      */
-    includeStatement : INCLUDE_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE revisionDateStatement? RIGHT_CURLY_BRACE);
+    includeStatement : INCLUDE_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE revisionDateStatement? RIGHT_CURLY_BRACE);
 
     /**
      * organization-stmt   = organization-keyword sep string
@@ -196,7 +196,7 @@
      *                                  [reference-stmt stmtsep]
      *                              "}")
      */
-    revisionStatement : REVISION_KEYWORD DATE_ARG (STMTEND | LEFT_CURLY_BRACE revisionStatementBody RIGHT_CURLY_BRACE);
+    revisionStatement : REVISION_KEYWORD dateArgumentString (STMTEND | LEFT_CURLY_BRACE revisionStatementBody RIGHT_CURLY_BRACE);
     revisionStatementBody : descriptionStatement? referenceStatement?;
 
     /**
@@ -210,7 +210,7 @@
      *                                 body-stmts
      *                             "}" optsep
      */
-    subModuleStatement : SUBMODULE_KEYWORD IDENTIFIER LEFT_CURLY_BRACE submoduleBody* RIGHT_CURLY_BRACE;
+    subModuleStatement : SUBMODULE_KEYWORD identifier LEFT_CURLY_BRACE submoduleBody* RIGHT_CURLY_BRACE;
     submoduleBody : submoduleHeaderStatement linkageStatements metaStatements revisionStatements bodyStatements;
 
     /** submodule-header-stmts =
@@ -229,7 +229,7 @@
      *                           prefix-stmt stmtsep
      *                       "}"
      */
-    belongstoStatement : BELONGS_TO_KEYWORD IDENTIFIER LEFT_CURLY_BRACE belongstoStatementBody RIGHT_CURLY_BRACE;
+    belongstoStatement : BELONGS_TO_KEYWORD identifier LEFT_CURLY_BRACE belongstoStatementBody RIGHT_CURLY_BRACE;
     belongstoStatementBody : prefixStatement;
 
     /**
@@ -243,7 +243,7 @@
      *                            [reference-stmt stmtsep]
      *                        "}")
      */
-    extensionStatement : EXTENSION_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE extensionBody RIGHT_CURLY_BRACE);
+    extensionStatement : EXTENSION_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE extensionBody RIGHT_CURLY_BRACE);
     extensionBody : argumentStatement? statusStatement? descriptionStatement? referenceStatement?
                    | argumentStatement? statusStatement? referenceStatement? descriptionStatement?
                    | argumentStatement? descriptionStatement? statusStatement? referenceStatement?
@@ -277,7 +277,7 @@
      *                            [yin-element-stmt stmtsep]
      *                        "}")
      */
-    argumentStatement : ARGUMENT_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE argumentBody RIGHT_CURLY_BRACE);
+    argumentStatement : ARGUMENT_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE argumentBody RIGHT_CURLY_BRACE);
     argumentBody : yinElementStatement?;
 
     /**
@@ -297,7 +297,7 @@
      *                            [reference-stmt stmtsep]
      *                        "}")
      */
-    identityStatement : IDENTITY_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE identityBody RIGHT_CURLY_BRACE);
+    identityStatement : IDENTITY_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE identityBody RIGHT_CURLY_BRACE);
     identityBody : baseStatement? statusStatement? descriptionStatement? referenceStatement?
                   | baseStatement? statusStatement? referenceStatement? descriptionStatement?
                   | baseStatement? descriptionStatement? statusStatement? referenceStatement?
@@ -410,7 +410,7 @@
      *                           "}"
      * TODO : 0..1 occurance to be validated in listener
      */
-    typedefStatement : TYPEDEF_KEYWORD IDENTIFIER LEFT_CURLY_BRACE
+    typedefStatement : TYPEDEF_KEYWORD identifier LEFT_CURLY_BRACE
                    (typeStatement | unitsStatement | defaultStatement | statusStatement | descriptionStatement | referenceStatement)*
                    RIGHT_CURLY_BRACE;
 
@@ -622,7 +622,7 @@
      *                          "}"
      *                        "}")
      */
-    bitStatement : BIT_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE bitBodyStatement RIGHT_CURLY_BRACE);
+    bitStatement : BIT_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE bitBodyStatement RIGHT_CURLY_BRACE);
 
     bitBodyStatement : positionStatement? statusStatement? descriptionStatement? referenceStatement?
                   | positionStatement? statusStatement? referenceStatement? descriptionStatement?
@@ -657,7 +657,7 @@
      *                              position-value-arg >
      *  position-value-arg  = non-negative-integer-value
      */
-    positionStatement : POSITION_KEYWORD INTEGER STMTEND;
+    positionStatement : POSITION_KEYWORD string STMTEND;
 
     /**
      *  status-stmt         = status-keyword sep status-arg-str stmtend
@@ -771,7 +771,7 @@
      *                         "}")
      * TODO : 0..1 occurance to be checked in listener
      */
-    groupingStatement : GROUPING_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE
+    groupingStatement : GROUPING_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE
                       (statusStatement | descriptionStatement | referenceStatement | typedefStatement | groupingStatement
                        | dataDefStatement)* RIGHT_CURLY_BRACE);
 
@@ -794,7 +794,7 @@
      *                         "}")
      * TODO : 0..1 occurance to be checked in listener
      */
-    containerStatement : CONTAINER_KEYWORD IDENTIFIER
+    containerStatement : CONTAINER_KEYWORD identifier
                      (STMTEND | LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | mustStatement | presenceStatement | configStatement
                      | statusStatement | descriptionStatement | referenceStatement | typedefStatement | groupingStatement
                      | dataDefStatement)* RIGHT_CURLY_BRACE);
@@ -817,7 +817,7 @@
      *                         "}"
      * TODO : 0..1 occurance to be checked in listener
      */
-    leafStatement : LEAF_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | typeStatement | unitsStatement
+    leafStatement : LEAF_KEYWORD identifier LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | typeStatement | unitsStatement
               | mustStatement | defaultStatement | configStatement | mandatoryStatement | statusStatement  | descriptionStatement
               | referenceStatement)* RIGHT_CURLY_BRACE;
 
@@ -840,7 +840,7 @@
      *                         "}"
      * TODO : 0..1 occurance to be checked in listener
      */
-    leafListStatement : LEAF_LIST_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | typeStatement
+    leafListStatement : LEAF_LIST_KEYWORD identifier LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | typeStatement
                      | unitsStatement | mustStatement | configStatement | minElementsStatement | maxElementsStatement | orderedByStatement
                      | statusStatement | descriptionStatement | referenceStatement)* RIGHT_CURLY_BRACE;
 
@@ -866,7 +866,7 @@
      *                         "}"
      * TODO : 0..1 occurance to be checked in listener
      */
-    listStatement : LIST_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | mustStatement | keyStatement
+    listStatement : LIST_KEYWORD identifier LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | mustStatement | keyStatement
               | uniqueStatement | configStatement | minElementsStatement | maxElementsStatement | orderedByStatement | statusStatement
               | descriptionStatement | referenceStatement | typedefStatement | groupingStatement| dataDefStatement)* RIGHT_CURLY_BRACE;
 
@@ -897,7 +897,7 @@
      *                         "}")
      * TODO : 0..1 occurance to be checked in listener
      */
-    choiceStatement : CHOICE_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | defaultStatement
+    choiceStatement : CHOICE_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | defaultStatement
                   | configStatement | mandatoryStatement | statusStatement | descriptionStatement | referenceStatement | shortCaseStatement
                   | caseStatement)* RIGHT_CURLY_BRACE);
 
@@ -924,7 +924,7 @@
      *                         "}")
      * TODO : 0..1 occurance to be checked in listener
      */
-    caseStatement : CASE_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | statusStatement
+    caseStatement : CASE_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | statusStatement
               | descriptionStatement | referenceStatement | dataDefStatement)* RIGHT_CURLY_BRACE);
 
     /**
@@ -1095,7 +1095,7 @@
      *                         "}")
      * TODO : 0..1 occurance to be checked in listener
      */
-    rpcStatement : RPC_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE (ifFeatureStatement | statusStatement | descriptionStatement
+    rpcStatement : RPC_KEYWORD identifier (STMTEND | LEFT_CURLY_BRACE (ifFeatureStatement | statusStatement | descriptionStatement
                 | referenceStatement | typedefStatement | groupingStatement | inputStatement | outputStatement)* RIGHT_CURLY_BRACE);
 
     /**
@@ -1223,3 +1223,9 @@
     string : STRING (PLUS STRING)*
            | IDENTIFIER
            | INTEGER;
+
+    identifier : STRING (PLUS STRING)*
+               | IDENTIFIER;
+
+    dateArgumentString : DATE_ARG
+                       | STRING (PLUS STRING)*;
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListenerTest.java
index 961e902..eeb85bb 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListenerTest.java
@@ -226,7 +226,7 @@
     @Test
     public void processContainerInvalidIdentifier() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("mismatched input '1valid' expecting IDENTIFIER");
+        thrown.expectMessage("YANG file error : container name 1valid is not valid.");
         YangNode node = manager.getDataModel("src/test/resources/ContainerInvalidIdentifier.yang");
     }
 }
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListenerTest.java
index afa48da..43abb45 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/LeafListListenerTest.java
@@ -85,7 +85,7 @@
     @Test
     public void processLeafListInvalidIdentifier() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("mismatched input '1invalid-interval' expecting IDENTIFIER");
+        thrown.expectMessage("YANG file error : leaf-list name 1invalid-interval is not valid.");
         YangNode node = manager.getDataModel("src/test/resources/LeafListInvalidIdentifier.yang");
     }
 
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/LeafListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/LeafListenerTest.java
index 40afc03..554d651 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/LeafListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/LeafListenerTest.java
@@ -85,7 +85,7 @@
     @Test
     public void processLeafInvalidIdentifier() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("mismatched input '1invalid-interval' expecting IDENTIFIER");
+        thrown.expectMessage("YANG file error : leaf name 1invalid-interval is not valid.");
         YangNode node = manager.getDataModel("src/test/resources/LeafInvalidIdentifier.yang");
     }
 
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ListListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ListListenerTest.java
index aa770a6..99d40dd 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ListListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ListListenerTest.java
@@ -205,7 +205,7 @@
     @Test
     public void processListInvalidIdentifier() throws IOException, ParserException {
         thrown.expect(ParserException.class);
-        thrown.expectMessage("mismatched input '1valid' expecting IDENTIFIER");
+        thrown.expectMessage("YANG file error : list name 1valid is not valid.");
         YangNode node = manager.getDataModel("src/test/resources/ListInvalidIdentifier.yang");
     }
 }
\ No newline at end of file
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListenerTest.java
index ab7242a..66d8e9a 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/ModuleListenerTest.java
@@ -16,7 +16,9 @@
 
 package org.onosproject.yangutils.parser.impl.listeners;
 
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNodeType;
@@ -35,6 +37,9 @@
 
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
 
+    @Rule
+    public ExpectedException thrown = ExpectedException.none();
+
     /**
      * Checks if module listener updates the data model root node.
      */
@@ -62,4 +67,15 @@
 
         YangNode node = manager.getDataModel("src/test/resources/ModuleWithInvalidIdentifier.yang");
     }
+
+    /**
+     * Checks whether exception is thrown when module length is greater than 64 characters.
+     */
+    @Test
+    public void processModuleInvalidIdentifierLength() throws IOException, ParserException {
+        thrown.expect(ParserException.class);
+        thrown.expectMessage("YANG file error : module name Testttttttttttttttttttttttttttttttttttttttttttttttttttt" +
+                "tttttttttt is greater than 64 characters.");
+        YangNode node = manager.getDataModel("src/test/resources/ModuleInvalidIdentifierLength.yang");
+    }
 }
\ No newline at end of file
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/PositionListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/PositionListenerTest.java
index 7033ddd..e0e2ab0 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/PositionListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/PositionListenerTest.java
@@ -80,6 +80,45 @@
     }
 
     /**
+     * Checks position value with double quotes.
+     */
+    @Test
+    public void processPositionWithDoubleQuotes() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/PositionWithDoubleQuotes.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        ListIterator<YangLeaf> leafIterator = yangNode.getListOfLeaf().listIterator();
+        YangLeaf leafInfo = leafIterator.next();
+
+        assertThat(leafInfo.getLeafName(), is("mybits"));
+        assertThat(leafInfo.getDataType().getDataTypeName(), is("bits"));
+        assertThat(leafInfo.getDataType().getDataType(), is(YangDataTypes.BITS));
+        assertThat(((YangBits) leafInfo.getDataType().getDataTypeExtendedInfo()).getBitsName(),
+                is("mybits"));
+
+        Set<YangBit> bitSet = ((YangBits) leafInfo.getDataType().getDataTypeExtendedInfo()).getBitSet();
+        for (YangBit tmp : bitSet) {
+            if (tmp.getBitName().equals("disable-nagle")) {
+                assertThat(tmp.getPosition(), is(0));
+            } else if (tmp.getBitName().equals("auto-sense-speed")) {
+                assertThat(tmp.getPosition(), is(1));
+            } else if (tmp.getBitName().equals("Ten-Mb-only")) {
+                assertThat(tmp.getPosition(), is(2));
+            }
+        }
+    }
+
+    /**
      * Checks explicit value and auto generated value.
      */
     @Test
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListenerTest.java
index b090bd0..3d7ff5c 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/PrefixListenerTest.java
@@ -56,6 +56,16 @@
     }
 
     /**
+     * Checks prefix value with double quotes.
+     */
+    @Test
+    public void processPrefixWithDoubleQuotes() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/PrefixWithDoubleQuotes.yang");
+        assertThat(((YangModule) node).getPrefix(), is("On"));
+    }
+
+    /**
      * Checks that prefix should be present just once.
      */
     @Test(expected = ParserException.class)
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListenerTest.java
index 7ebcc85..7f19219 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/RevisionDateListenerTest.java
@@ -53,21 +53,29 @@
     }
 
     /**
-     * Checks revision date should not be in quotes inside include.
+     * Checks revision date in quotes inside include.
      */
-    @Test(expected = ParserException.class)
+    @Test
     public void processRevisionDateInQuotesAtInclude() throws IOException, ParserException {
 
         YangNode node = manager.getDataModel("src/test/resources/RevisionDateInQuotesAtInclude.yang");
+        // Checks for the version value in data model tree.
+        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is("2015-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is("2016-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is("2014-02-03"));
     }
 
     /**
-     * Checks revision date should not be in quotes inside import.
+     * Checks revision date in quotes inside import.
      */
-    @Test(expected = ParserException.class)
+    @Test
     public void processRevisionDateInQuotesAtImport() throws IOException, ParserException {
 
         YangNode node = manager.getDataModel("src/test/resources/RevisionDateInQuotesAtImport.yang");
+        // Checks for the version value in data model tree.
+        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is("2015-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is("2016-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is("2014-02-03"));
     }
 
     /**
diff --git a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/VersionListenerTest.java b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/VersionListenerTest.java
index 07df80c..324fe1e 100644
--- a/src/test/java/org/onosproject/yangutils/parser/impl/listeners/VersionListenerTest.java
+++ b/src/test/java/org/onosproject/yangutils/parser/impl/listeners/VersionListenerTest.java
@@ -56,6 +56,18 @@
     }
 
     /**
+     * Checks version in double quotes.
+     */
+    @Test
+    public void processValidVersionWithDoubleQuotes() throws IOException, ParserException {
+
+        YangNode node = manager.getDataModel("src/test/resources/ValidVersionWithDoubleQuotes.yang");
+
+        // Checks for the version value in data model tree.
+        assertThat(((YangModule) node).getVersion(), is((byte) 1));
+    }
+
+    /**
      * Checks if version which is optional paramater is not present.
      */
     @Test
diff --git a/src/test/resources/ModuleInvalidIdentifierLength.yang b/src/test/resources/ModuleInvalidIdentifierLength.yang
new file mode 100644
index 0000000..fac16bc
--- /dev/null
+++ b/src/test/resources/ModuleInvalidIdentifierLength.yang
@@ -0,0 +1,5 @@
+module Testttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt {
+yang-version 1;
+namespace urn:ietf:params:xml:ns:yang:ietf-ospf;
+prefix On;
+}
diff --git a/src/test/resources/PositionWithDoubleQuotes.yang b/src/test/resources/PositionWithDoubleQuotes.yang
new file mode 100644
index 0000000..0c9d358
--- /dev/null
+++ b/src/test/resources/PositionWithDoubleQuotes.yang
@@ -0,0 +1,18 @@
+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+     leaf mybits {
+         type bits {
+             bit disable-nagle {
+                 position "0";
+             }
+             bit auto-sense-speed {
+                 position "1";
+             }
+             bit Ten-Mb-only {
+                 position "2";
+             }
+         }
+    }
+}
diff --git a/src/test/resources/PrefixWithDoubleQuotes.yang b/src/test/resources/PrefixWithDoubleQuotes.yang
new file mode 100644
index 0000000..e9590f1
--- /dev/null
+++ b/src/test/resources/PrefixWithDoubleQuotes.yang
@@ -0,0 +1,17 @@
+module Test {
+yang-version 1;
+namespace urn:ietf:params:xml:ns:yang:ietf-ospf;
+prefix "On";
+import ietf {
+prefix On2;
+revision-date 2015-02-03;
+}
+include itut {
+revision-date 2016-02-03;
+}
+include sdn {
+revision-date 2014-02-03;
+}
+contact "Test";
+organization "ONOS";
+}
diff --git a/src/test/resources/ValidVersionWithDoubleQuotes.yang b/src/test/resources/ValidVersionWithDoubleQuotes.yang
new file mode 100644
index 0000000..a2c718a
--- /dev/null
+++ b/src/test/resources/ValidVersionWithDoubleQuotes.yang
@@ -0,0 +1,5 @@
+module Test {
+yang-version "1";
+namespace urn:ietf:params:xml:ns:yang:ietf-ospf;
+prefix On;
+}