YANG sub module linking + unsupported yang construct + defect fix

Change-Id: I224c8c14ee2111f6844278cb540c48651544f59b
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/TreeWalkListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/TreeWalkListener.java
index 5c03e54..370b56c 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/TreeWalkListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/TreeWalkListener.java
@@ -75,6 +75,11 @@
 import org.onosproject.yangutils.parser.impl.listeners.UsesListener;
 import org.onosproject.yangutils.parser.impl.listeners.ValueListener;
 import org.onosproject.yangutils.parser.impl.listeners.VersionListener;
+import org.onosproject.yangutils.utils.YangConstructType;
+
+import static org.onosproject.yangutils.utils.UtilConstants.UNSUPPORTED_YANG_CONSTRUCT;
+import static org.onosproject.yangutils.utils.UtilConstants.CURRENTLY_UNSUPPORTED;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.handleUnsupportedYangConstruct;
 
 /**
  * Represents ANTLR generates parse-tree. ANTLR generates a parse-tree listener interface that responds to events
@@ -148,62 +153,62 @@
 
     @Override
     public void enterModuleBody(GeneratedYangParser.ModuleBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitModuleBody(GeneratedYangParser.ModuleBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterModuleHeaderStatement(GeneratedYangParser.ModuleHeaderStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitModuleHeaderStatement(GeneratedYangParser.ModuleHeaderStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterLinkageStatements(GeneratedYangParser.LinkageStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitLinkageStatements(GeneratedYangParser.LinkageStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterMetaStatements(GeneratedYangParser.MetaStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitMetaStatements(GeneratedYangParser.MetaStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRevisionStatements(GeneratedYangParser.RevisionStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRevisionStatements(GeneratedYangParser.RevisionStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterBodyStatements(GeneratedYangParser.BodyStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitBodyStatements(GeneratedYangParser.BodyStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -213,7 +218,7 @@
 
     @Override
     public void exitYangVersionStatement(GeneratedYangParser.YangVersionStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -223,7 +228,7 @@
 
     @Override
     public void exitNamespaceStatement(GeneratedYangParser.NamespaceStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -233,7 +238,7 @@
 
     @Override
     public void exitPrefixStatement(GeneratedYangParser.PrefixStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -248,12 +253,12 @@
 
     @Override
     public void enterImportStatementBody(GeneratedYangParser.ImportStatementBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitImportStatementBody(GeneratedYangParser.ImportStatementBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -263,7 +268,7 @@
 
     @Override
     public void exitRevisionDateStatement(GeneratedYangParser.RevisionDateStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -283,7 +288,7 @@
 
     @Override
     public void exitOrganizationStatement(GeneratedYangParser.OrganizationStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -293,7 +298,7 @@
 
     @Override
     public void exitContactStatement(GeneratedYangParser.ContactStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -303,7 +308,7 @@
 
     @Override
     public void exitDescriptionStatement(GeneratedYangParser.DescriptionStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -313,7 +318,7 @@
 
     @Override
     public void exitReferenceStatement(GeneratedYangParser.ReferenceStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -328,12 +333,12 @@
 
     @Override
     public void enterRevisionStatementBody(GeneratedYangParser.RevisionStatementBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRevisionStatementBody(GeneratedYangParser.RevisionStatementBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -348,22 +353,22 @@
 
     @Override
     public void enterSubmoduleBody(GeneratedYangParser.SubmoduleBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitSubmoduleBody(GeneratedYangParser.SubmoduleBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterSubmoduleHeaderStatement(GeneratedYangParser.SubmoduleHeaderStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitSubmoduleHeaderStatement(GeneratedYangParser.SubmoduleHeaderStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -378,132 +383,132 @@
 
     @Override
     public void enterBelongstoStatementBody(GeneratedYangParser.BelongstoStatementBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitBelongstoStatementBody(GeneratedYangParser.BelongstoStatementBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterExtensionStatement(GeneratedYangParser.ExtensionStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.EXTENSION_DATA, ctx, UNSUPPORTED_YANG_CONSTRUCT);
     }
 
     @Override
     public void exitExtensionStatement(GeneratedYangParser.ExtensionStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing
     }
 
     @Override
     public void enterExtensionBody(GeneratedYangParser.ExtensionBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitExtensionBody(GeneratedYangParser.ExtensionBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterArgumentStatement(GeneratedYangParser.ArgumentStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitArgumentStatement(GeneratedYangParser.ArgumentStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterArgumentBody(GeneratedYangParser.ArgumentBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitArgumentBody(GeneratedYangParser.ArgumentBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterYinElementStatement(GeneratedYangParser.YinElementStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitYinElementStatement(GeneratedYangParser.YinElementStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterIdentityStatement(GeneratedYangParser.IdentityStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.IDENTITY_DATA, ctx, CURRENTLY_UNSUPPORTED);
     }
 
     @Override
     public void exitIdentityStatement(GeneratedYangParser.IdentityStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterIdentityBody(GeneratedYangParser.IdentityBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitIdentityBody(GeneratedYangParser.IdentityBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterBaseStatement(GeneratedYangParser.BaseStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.BASE_DATA, ctx, CURRENTLY_UNSUPPORTED);
     }
 
     @Override
     public void exitBaseStatement(GeneratedYangParser.BaseStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterFeatureStatement(GeneratedYangParser.FeatureStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.FEATURE_DATA, ctx, CURRENTLY_UNSUPPORTED);
     }
 
     @Override
     public void exitFeatureStatement(GeneratedYangParser.FeatureStatementContext ctx) {
-        // TODO: implement the method.
+        //TODO: to be implemented
     }
 
     @Override
     public void enterFeatureBody(GeneratedYangParser.FeatureBodyContext ctx) {
-        // TODO: implement the method.
+        //TODO : to be implemented
     }
 
     @Override
     public void exitFeatureBody(GeneratedYangParser.FeatureBodyContext ctx) {
-        // TODO: implement the method.
+        //TODO : to be implemented
     }
 
     @Override
     public void enterDataDefStatement(GeneratedYangParser.DataDefStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitDataDefStatement(GeneratedYangParser.DataDefStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterIfFeatureStatement(GeneratedYangParser.IfFeatureStatementContext ctx) {
-        // TODO: implement the method.
+        // TODO: to be implemented
     }
 
     @Override
     public void exitIfFeatureStatement(GeneratedYangParser.IfFeatureStatementContext ctx) {
-        // TODO: implement the method.
+        // TODO: to be implemented
     }
 
     @Override
@@ -513,7 +518,7 @@
 
     @Override
     public void exitUnitsStatement(GeneratedYangParser.UnitsStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -538,22 +543,32 @@
 
     @Override
     public void enterTypeBodyStatements(GeneratedYangParser.TypeBodyStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitTypeBodyStatements(GeneratedYangParser.TypeBodyStatementsContext ctx) {
+        // do nothing.
+    }
+
+    @Override
+    public void enterDecimal64Specification(GeneratedYangParser.Decimal64SpecificationContext ctx) {
+        // TODO: implement the method.
+    }
+
+    @Override
+    public void exitDecimal64Specification(GeneratedYangParser.Decimal64SpecificationContext ctx) {
         // TODO: implement the method.
     }
 
     @Override
     public void enterNumericalRestrictions(GeneratedYangParser.NumericalRestrictionsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitNumericalRestrictions(GeneratedYangParser.NumericalRestrictionsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -563,27 +578,27 @@
 
     @Override
     public void exitRangeStatement(GeneratedYangParser.RangeStatementContext ctx) {
-        // TODO: implement the method.
+        RangeRestrictionListener.processRangeRestrictionExit(this, ctx);
     }
 
     @Override
     public void enterCommonStatements(GeneratedYangParser.CommonStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitCommonStatements(GeneratedYangParser.CommonStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterStringRestrictions(GeneratedYangParser.StringRestrictionsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitStringRestrictions(GeneratedYangParser.StringRestrictionsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -593,7 +608,7 @@
 
     @Override
     public void exitLengthStatement(GeneratedYangParser.LengthStatementContext ctx) {
-        // TODO: implement the method.
+        LengthRestrictionListener.processLengthRestrictionExit(this, ctx);
     }
 
     @Override
@@ -603,7 +618,7 @@
 
     @Override
     public void exitPatternStatement(GeneratedYangParser.PatternStatementContext ctx) {
-        // TODO: implement the method.
+        PatternRestrictionListener.processPatternRestrictionExit(this, ctx);
     }
 
     @Override
@@ -613,7 +628,7 @@
 
     @Override
     public void exitDefaultStatement(GeneratedYangParser.DefaultStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -638,62 +653,62 @@
 
     @Override
     public void enterEnumStatementBody(GeneratedYangParser.EnumStatementBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitEnumStatementBody(GeneratedYangParser.EnumStatementBodyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterLeafrefSpecification(GeneratedYangParser.LeafrefSpecificationContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitLeafrefSpecification(GeneratedYangParser.LeafrefSpecificationContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterPathStatement(GeneratedYangParser.PathStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.PATH_DATA, ctx, CURRENTLY_UNSUPPORTED);
     }
 
     @Override
     public void exitPathStatement(GeneratedYangParser.PathStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRequireInstanceStatement(GeneratedYangParser.RequireInstanceStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.REQUIRE_INSTANCE_DATA, ctx, UNSUPPORTED_YANG_CONSTRUCT);
     }
 
     @Override
     public void exitRequireInstanceStatement(GeneratedYangParser.RequireInstanceStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterInstanceIdentifierSpecification(GeneratedYangParser.InstanceIdentifierSpecificationContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitInstanceIdentifierSpecification(GeneratedYangParser.InstanceIdentifierSpecificationContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterIdentityrefSpecification(GeneratedYangParser.IdentityrefSpecificationContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitIdentityrefSpecification(GeneratedYangParser.IdentityrefSpecificationContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -728,12 +743,12 @@
 
     @Override
     public void enterBitBodyStatement(GeneratedYangParser.BitBodyStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitBitBodyStatement(GeneratedYangParser.BitBodyStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -743,7 +758,7 @@
 
     @Override
     public void exitPositionStatement(GeneratedYangParser.PositionStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -753,7 +768,7 @@
 
     @Override
     public void exitStatusStatement(GeneratedYangParser.StatusStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -763,7 +778,7 @@
 
     @Override
     public void exitConfigStatement(GeneratedYangParser.ConfigStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -773,7 +788,7 @@
 
     @Override
     public void exitMandatoryStatement(GeneratedYangParser.MandatoryStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -783,47 +798,47 @@
 
     @Override
     public void exitPresenceStatement(GeneratedYangParser.PresenceStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterOrderedByStatement(GeneratedYangParser.OrderedByStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.ORDERED_BY_DATA, ctx, CURRENTLY_UNSUPPORTED);
     }
 
     @Override
     public void exitOrderedByStatement(GeneratedYangParser.OrderedByStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterMustStatement(GeneratedYangParser.MustStatementContext ctx) {
-        // TODO: implement the method.
+        // TODO: to be implemented
     }
 
     @Override
     public void exitMustStatement(GeneratedYangParser.MustStatementContext ctx) {
-        // TODO: implement the method.
+        // TODO: to be implemented
     }
 
     @Override
     public void enterErrorMessageStatement(GeneratedYangParser.ErrorMessageStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.ERROR_MESSAGE_DATA, ctx, CURRENTLY_UNSUPPORTED);
     }
 
     @Override
     public void exitErrorMessageStatement(GeneratedYangParser.ErrorMessageStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterErrorAppTagStatement(GeneratedYangParser.ErrorAppTagStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.ERROR_APP_TAG_DATA, ctx, CURRENTLY_UNSUPPORTED);
     }
 
     @Override
     public void exitErrorAppTagStatement(GeneratedYangParser.ErrorAppTagStatementContext ctx) {
-        // TODO: implement the method.
+        //do nothing
     }
 
     @Override
@@ -833,7 +848,7 @@
 
     @Override
     public void exitMinElementsStatement(GeneratedYangParser.MinElementsStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -843,7 +858,7 @@
 
     @Override
     public void exitMaxElementsStatement(GeneratedYangParser.MaxElementsStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -853,7 +868,7 @@
 
     @Override
     public void exitValueStatement(GeneratedYangParser.ValueStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -913,17 +928,17 @@
 
     @Override
     public void exitKeyStatement(GeneratedYangParser.KeyStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterUniqueStatement(GeneratedYangParser.UniqueStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.UNIQUE_DATA, ctx, CURRENTLY_UNSUPPORTED);
     }
 
     @Override
     public void exitUniqueStatement(GeneratedYangParser.UniqueStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
@@ -957,6 +972,16 @@
     }
 
     @Override
+    public void enterAnyxmlStatement(GeneratedYangParser.AnyxmlStatementContext ctx) {
+        handleUnsupportedYangConstruct(YangConstructType.ANYXML_DATA, ctx, UNSUPPORTED_YANG_CONSTRUCT);
+    }
+
+    @Override
+    public void exitAnyxmlStatement(GeneratedYangParser.AnyxmlStatementContext ctx) {
+        // do nothing.
+    }
+
+    @Override
     public void enterUsesStatement(GeneratedYangParser.UsesStatementContext ctx) {
         UsesListener.processUsesEntry(this, ctx);
     }
@@ -968,82 +993,82 @@
 
     @Override
     public void enterRefineStatement(GeneratedYangParser.RefineStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.REFINE_DATA, ctx, UNSUPPORTED_YANG_CONSTRUCT);
     }
 
     @Override
     public void exitRefineStatement(GeneratedYangParser.RefineStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRefineContainerStatements(GeneratedYangParser.RefineContainerStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRefineContainerStatements(GeneratedYangParser.RefineContainerStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRefineLeafStatements(GeneratedYangParser.RefineLeafStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRefineLeafStatements(GeneratedYangParser.RefineLeafStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRefineLeafListStatements(GeneratedYangParser.RefineLeafListStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRefineLeafListStatements(GeneratedYangParser.RefineLeafListStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRefineListStatements(GeneratedYangParser.RefineListStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRefineListStatements(GeneratedYangParser.RefineListStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRefineChoiceStatements(GeneratedYangParser.RefineChoiceStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRefineChoiceStatements(GeneratedYangParser.RefineChoiceStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRefineCaseStatements(GeneratedYangParser.RefineCaseStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRefineCaseStatements(GeneratedYangParser.RefineCaseStatementsContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
-    public void enterUsesAugmentStatement(GeneratedYangParser.UsesAugmentStatementContext ctx) {
-        // TODO: implement the method.
+    public void enterRefineAnyxmlStatements(GeneratedYangParser.RefineAnyxmlStatementsContext ctx) {
+        // do nothing.
     }
 
     @Override
-    public void exitUsesAugmentStatement(GeneratedYangParser.UsesAugmentStatementContext ctx) {
-        // TODO: implement the method.
+    public void exitRefineAnyxmlStatements(GeneratedYangParser.RefineAnyxmlStatementsContext ctx) {
+        // do nothing.
     }
 
     @Override
@@ -1058,12 +1083,12 @@
 
     @Override
     public void enterWhenStatement(GeneratedYangParser.WhenStatementContext ctx) {
-        // TODO: implement the method.
+        // TODO: to be implemented
     }
 
     @Override
     public void exitWhenStatement(GeneratedYangParser.WhenStatementContext ctx) {
-        // TODO: implement the method.
+        // TODO: to be implemented
     }
 
     @Override
@@ -1108,271 +1133,291 @@
 
     @Override
     public void enterDeviationStatement(GeneratedYangParser.DeviationStatementContext ctx) {
-        // TODO: implement the method.
+        handleUnsupportedYangConstruct(YangConstructType.DEVIATION_DATA, ctx, UNSUPPORTED_YANG_CONSTRUCT);
     }
 
     @Override
     public void exitDeviationStatement(GeneratedYangParser.DeviationStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterDeviateNotSupportedStatement(GeneratedYangParser.DeviateNotSupportedStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitDeviateNotSupportedStatement(GeneratedYangParser.DeviateNotSupportedStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterDeviateAddStatement(GeneratedYangParser.DeviateAddStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitDeviateAddStatement(GeneratedYangParser.DeviateAddStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterDeviateDeleteStatement(GeneratedYangParser.DeviateDeleteStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitDeviateDeleteStatement(GeneratedYangParser.DeviateDeleteStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterDeviateReplaceStatement(GeneratedYangParser.DeviateReplaceStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitDeviateReplaceStatement(GeneratedYangParser.DeviateReplaceStatementContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterString(GeneratedYangParser.StringContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitString(GeneratedYangParser.StringContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterIdentifier(GeneratedYangParser.IdentifierContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitIdentifier(GeneratedYangParser.IdentifierContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterDateArgumentString(GeneratedYangParser.DateArgumentStringContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitDateArgumentString(GeneratedYangParser.DateArgumentStringContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRange(GeneratedYangParser.RangeContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRange(GeneratedYangParser.RangeContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterLength(GeneratedYangParser.LengthContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitLength(GeneratedYangParser.LengthContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterPath(GeneratedYangParser.PathContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitPath(GeneratedYangParser.PathContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterPosition(GeneratedYangParser.PositionContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitPosition(GeneratedYangParser.PositionContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterStatus(GeneratedYangParser.StatusContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitStatus(GeneratedYangParser.StatusContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterConfig(GeneratedYangParser.ConfigContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitConfig(GeneratedYangParser.ConfigContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterMandatory(GeneratedYangParser.MandatoryContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitMandatory(GeneratedYangParser.MandatoryContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterOrderedBy(GeneratedYangParser.OrderedByContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitOrderedBy(GeneratedYangParser.OrderedByContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterMinValue(GeneratedYangParser.MinValueContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitMinValue(GeneratedYangParser.MinValueContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterMaxValue(GeneratedYangParser.MaxValueContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitMaxValue(GeneratedYangParser.MaxValueContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterKey(GeneratedYangParser.KeyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitKey(GeneratedYangParser.KeyContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterUnique(GeneratedYangParser.UniqueContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitUnique(GeneratedYangParser.UniqueContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterRefine(GeneratedYangParser.RefineContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitRefine(GeneratedYangParser.RefineContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterAugment(GeneratedYangParser.AugmentContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitAugment(GeneratedYangParser.AugmentContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterDeviation(GeneratedYangParser.DeviationContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitDeviation(GeneratedYangParser.DeviationContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterYangConstruct(GeneratedYangParser.YangConstructContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitYangConstruct(GeneratedYangParser.YangConstructContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterVersion(GeneratedYangParser.VersionContext ctx) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitVersion(GeneratedYangParser.VersionContext ctx) {
+        // do nothing.
+    }
+
+    @Override
+    public void enterValue(GeneratedYangParser.ValueContext ctx) {
+        // do nothing.
+    }
+
+    @Override
+    public void exitValue(GeneratedYangParser.ValueContext ctx) {
+        // do nothing.
+    }
+
+    @Override
+    public void enterFraction(GeneratedYangParser.FractionContext ctx) {
+        // TODO: implement the method.
+    }
+
+    @Override
+    public void exitFraction(GeneratedYangParser.FractionContext ctx) {
         // TODO: implement the method.
     }
 
     @Override
     public void visitTerminal(TerminalNode terminalNode) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void visitErrorNode(ErrorNode errorNode) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void enterEveryRule(ParserRuleContext parserRuleContext) {
-        // TODO: implement the method.
+        // do nothing.
     }
 
     @Override
     public void exitEveryRule(ParserRuleContext parserRuleContext) {
-        // TODO: implement the method.
+        // do nothing.
     }
 }
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
index 643499f..72bd97a 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
@@ -26,6 +26,7 @@
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNotification;
 import org.onosproject.yangutils.datamodel.YangOutput;
+import org.onosproject.yangutils.datamodel.YangSubModule;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
@@ -133,12 +134,11 @@
         }
 
         Parsable curData = listener.getParsedDataStack().peek();
-        if (curData instanceof YangModule || curData instanceof YangContainer
-                || curData instanceof YangList || curData instanceof YangCase
-                || curData instanceof YangNotification
+        if (curData instanceof YangModule || curData instanceof YangSubModule
+                || curData instanceof YangContainer || curData instanceof YangList
+                || curData instanceof YangCase || curData instanceof YangNotification
                 || curData instanceof YangInput || curData instanceof YangOutput
-                || curData instanceof YangAugment
-                || curData instanceof YangGrouping) {
+                || curData instanceof YangAugment || curData instanceof YangGrouping) {
             YangNode curNode = (YangNode) curData;
             try {
                 curNode.addChild(container);
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/DefaultListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/DefaultListener.java
index fc9b84a..a4511bc 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/DefaultListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/DefaultListener.java
@@ -39,6 +39,8 @@
  * defaultStatement : DEFAULT_KEYWORD string STMTEND;
  */
 
+import org.onosproject.yangutils.datamodel.YangChoice;
+import org.onosproject.yangutils.datamodel.YangLeaf;
 import org.onosproject.yangutils.datamodel.YangTypeDef;
 import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
@@ -83,6 +85,16 @@
                 typeDef.setDefaultValueInString(ctx.string().getText());
                 break;
             }
+            case LEAF_DATA: {
+                YangLeaf leaf = (YangLeaf) tmpNode;
+                leaf.setDefaultValueInString(ctx.string().getText());
+                break;
+            }
+            case CHOICE_DATA: {
+                YangChoice choice = (YangChoice) tmpNode;
+                choice.setDefaultValueInString(ctx.string().getText());
+                break;
+            }
             default:
                 throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER,
                         DEFAULT_DATA, ctx.string().getText(), ENTRY));
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumListener.java
index 08edab1..e0a51df 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumListener.java
@@ -146,7 +146,14 @@
                         boolean isValuePresent = false;
 
                         for (YangEnum curEnum : yangEnumeration.getEnumSet()) {
-                            if (maxValue <= curEnum.getValue()) {
+                            if (curEnum.getValue() == Integer.MAX_VALUE) {
+                                ParserException parserException = new ParserException("YANG file error : "
+                                        + "An enum value MUST be specified for enum substatements following the one"
+                                        + "with the current highest value");
+                                parserException.setLine(ctx.getStart().getLine());
+                                parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+                                throw parserException;
+                            } else if (maxValue <= curEnum.getValue()) {
                                 maxValue = curEnum.getValue();
                                 isValuePresent = true;
                             }
@@ -161,8 +168,8 @@
                     } catch (DataModelException e) {
                         ParserException parserException = new ParserException(constructExtendedListenerErrorMessage(
                                 DUPLICATE_ENTRY, ENUM_DATA, ctx.string().getText(), EXIT, e.getMessage()));
-                        parserException.setLine(ctx.string().STRING(0).getSymbol().getLine());
-                        parserException.setCharPosition(ctx.string().STRING(0).getSymbol().getCharPositionInLine());
+                        parserException.setLine(ctx.getStart().getLine());
+                        parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
                         throw parserException;
                     }
                     break;
@@ -173,8 +180,7 @@
             }
         } else {
             throw new ParserException(
-                    constructListenerErrorMessage(MISSING_CURRENT_HOLDER, ENUM_DATA, ctx.string().getText(),
-                            EXIT));
+                    constructListenerErrorMessage(MISSING_CURRENT_HOLDER, ENUM_DATA, ctx.string().getText(), EXIT));
         }
     }
 }
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LengthRestrictionListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LengthRestrictionListener.java
index 03fc737..2f1d7fe 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LengthRestrictionListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/LengthRestrictionListener.java
@@ -29,8 +29,10 @@
 
 import static org.onosproject.yangutils.datamodel.YangDataTypes.DERIVED;
 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;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+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.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.utils.RestrictionResolver.processLengthRestriction;
@@ -86,7 +88,7 @@
         Parsable tmpData = listener.getParsedDataStack().peek();
         if (tmpData.getYangConstructType() == TYPE_DATA) {
             YangType type = (YangType) tmpData;
-            setLengthRestriction(type, ctx);
+            setLengthRestriction(listener, type, ctx);
         } else {
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, LENGTH_DATA,
                     ctx.length().getText(), ENTRY));
@@ -96,10 +98,11 @@
     /**
      * Sets the length restriction to type.
      *
+     * @param listener listener's object
      * @param type Yang type for which length restriction to be set
      * @param ctx  context object of the grammar rule
      */
-    private static void setLengthRestriction(YangType type,
+    private static void setLengthRestriction(TreeWalkListener listener, YangType type,
                                              GeneratedYangParser.LengthStatementContext ctx) {
 
         if (type.getDataType() == DERIVED) {
@@ -132,5 +135,31 @@
         }
 
         stringRestriction.setLengthRestriction(lengthRestriction);
+        listener.getParsedDataStack().push(lengthRestriction);
+    }
+
+    /**
+     * Performs validation and updates the data model tree.
+     * It is called when parser exits from grammar rule (length).
+     *
+     * @param listener listener's object
+     * @param ctx context object of the grammar rule
+     */
+    public static void processLengthRestrictionExit(TreeWalkListener listener,
+                                                   GeneratedYangParser.LengthStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, LENGTH_DATA, ctx.length().getText(), EXIT);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        if (tmpData instanceof YangRangeRestriction) {
+            listener.getParsedDataStack().pop();
+        } else if (tmpData instanceof YangType
+                && ((YangType) tmpData).getDataType() == DERIVED) {
+            // TODO : need to handle in linker
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, LENGTH_DATA,
+                    ctx.length().getText(), EXIT));
+        }
     }
 }
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
index 42326b7..1f4ab50 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ListListener.java
@@ -26,6 +26,7 @@
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNotification;
 import org.onosproject.yangutils.datamodel.YangOutput;
+import org.onosproject.yangutils.datamodel.YangSubModule;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.parser.Parsable;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
@@ -141,7 +142,8 @@
         if (curData instanceof YangModule || curData instanceof YangContainer
                 || curData instanceof YangList || curData instanceof YangCase
                 || curData instanceof YangNotification || curData instanceof YangInput
-                || curData instanceof YangOutput || curData instanceof YangAugment || curData instanceof YangGrouping) {
+                || curData instanceof YangOutput || curData instanceof YangAugment
+                || curData instanceof YangGrouping || curData instanceof YangSubModule) {
             curNode = (YangNode) curData;
             try {
                 curNode.addChild(yangList);
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PatternRestrictionListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PatternRestrictionListener.java
index 3c1fd5a..ca36525 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PatternRestrictionListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PatternRestrictionListener.java
@@ -27,9 +27,12 @@
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
 import org.onosproject.yangutils.utils.YangConstructType;
 
+import static org.onosproject.yangutils.datamodel.YangDataTypes.DERIVED;
 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;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+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.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.utils.YangConstructType.PATTERN_DATA;
@@ -84,7 +87,7 @@
         Parsable tmpData = listener.getParsedDataStack().peek();
         if (tmpData.getYangConstructType() == TYPE_DATA) {
             YangType type = (YangType) tmpData;
-            setPatternRestriction(type, ctx);
+            setPatternRestriction(listener, type, ctx);
         } else {
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, PATTERN_DATA,
                     ctx.string().getText(), ENTRY));
@@ -94,10 +97,11 @@
     /**
      * Sets the pattern restriction to type.
      *
+     * @param listener listener's object
      * @param type Yang type for which pattern restriction to be set
      * @param ctx  context object of the grammar rule
      */
-    private static void setPatternRestriction(YangType type,
+    private static void setPatternRestriction(TreeWalkListener listener, YangType type,
                                               GeneratedYangParser.PatternStatementContext ctx) {
 
         if (type.getDataType() != YangDataTypes.STRING && type.getDataType() != YangDataTypes.DERIVED) {
@@ -121,6 +125,7 @@
             } else {
                 stringRestriction.addPattern(patternArgument);
             }
+            listener.getParsedDataStack().push(stringRestriction);
         } else {
             YangPatternRestriction patternRestriction = (YangPatternRestriction) ((YangDerivedInfo<?>) type
                     .getDataTypeExtendedInfo()).getPatternRestriction();
@@ -134,4 +139,29 @@
             }
         }
     }
+
+    /**
+     * Performs validation and updates the data model tree.
+     * It is called when parser exits from grammar rule (pattern).
+     *
+     * @param listener listener's object
+     * @param ctx context object of the grammar rule
+     */
+    public static void processPatternRestrictionExit(TreeWalkListener listener,
+                                                    GeneratedYangParser.PatternStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, PATTERN_DATA, ctx.string().getText(), EXIT);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        if (tmpData instanceof YangStringRestriction) {
+            listener.getParsedDataStack().pop();
+        } else if (tmpData instanceof YangType
+                && ((YangType) tmpData).getDataType() == DERIVED) {
+            // TODO : need to handle in linker
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, PATTERN_DATA,
+                    ctx.string().getText(), EXIT));
+        }
+    }
 }
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RangeRestrictionListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RangeRestrictionListener.java
index b6e0cf6..b0387ae 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RangeRestrictionListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/RangeRestrictionListener.java
@@ -26,8 +26,10 @@
 
 import static org.onosproject.yangutils.datamodel.YangDataTypes.DERIVED;
 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;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+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.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.utils.RestrictionResolver.isOfRangeRestrictedType;
@@ -82,7 +84,7 @@
         Parsable tmpData = listener.getParsedDataStack().peek();
         if (tmpData.getYangConstructType() == TYPE_DATA) {
             YangType type = (YangType) tmpData;
-            setRangeRestriction(type, ctx);
+            setRangeRestriction(listener, type, ctx);
         } else {
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, RANGE_DATA,
                     ctx.range().getText(), ENTRY));
@@ -92,10 +94,11 @@
     /**
      * Sets the range restriction to type.
      *
+     * @param listener listener's object
      * @param type YANG type for which range restriction to be added
      * @param ctx  context object of the grammar rule
      */
-    private static void setRangeRestriction(YangType type,
+    private static void setRangeRestriction(TreeWalkListener listener, YangType type,
                                             GeneratedYangParser.RangeStatementContext ctx) {
 
         if (type.getDataType() == DERIVED) {
@@ -122,5 +125,31 @@
         if (rangeRestriction != null) {
             type.setDataTypeExtendedInfo(rangeRestriction);
         }
+        listener.getParsedDataStack().push(rangeRestriction);
+    }
+
+    /**
+     * Performs validation and updates the data model tree.
+     * It is called when parser exits from grammar rule (range).
+     *
+     * @param listener listener's object
+     * @param ctx context object of the grammar rule
+     */
+    public static void processRangeRestrictionExit(TreeWalkListener listener,
+                                       GeneratedYangParser.RangeStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, RANGE_DATA, ctx.range().getText(), EXIT);
+
+        Parsable tmpData = listener.getParsedDataStack().peek();
+        if (tmpData instanceof YangRangeRestriction) {
+            listener.getParsedDataStack().pop();
+        } else if (tmpData instanceof YangType
+                && ((YangType) tmpData).getDataType() == DERIVED) {
+            // TODO : need to handle in linker
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, RANGE_DATA,
+                    ctx.range().getText(), EXIT));
+        }
     }
 }
\ No newline at end of file
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ValueListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ValueListener.java
index 92a0d42..cd54436 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ValueListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ValueListener.java
@@ -38,6 +38,7 @@
 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.ListenerValidation.checkStackIsNotEmpty;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIntegerValue;
 import static org.onosproject.yangutils.utils.YangConstructType.VALUE_DATA;
 
 /**
@@ -62,25 +63,28 @@
     public static void processValueEntry(TreeWalkListener listener, GeneratedYangParser.ValueStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, VALUE_DATA, ctx.INTEGER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, VALUE_DATA, ctx.value().getText(), ENTRY);
+
+        // Validate value
+        int value = getValidIntegerValue(ctx.value().getText(), VALUE_DATA, ctx);
 
         // Obtain the node of the stack.
         Parsable tmpNode = listener.getParsedDataStack().peek();
         switch (tmpNode.getYangConstructType()) {
             case ENUM_DATA: {
                 YangEnum enumNode = (YangEnum) tmpNode;
-                if (!isEnumValueValid(listener, ctx)) {
+                if (!isEnumValueValid(listener, ctx, value)) {
                     ParserException parserException = new ParserException("Duplicate Value Entry");
-                    parserException.setLine(ctx.INTEGER().getSymbol().getLine());
-                    parserException.setCharPosition(ctx.INTEGER().getSymbol().getCharPositionInLine());
+                    parserException.setLine(ctx.getStart().getLine());
+                    parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
                     throw parserException;
                 }
-                enumNode.setValue(Integer.valueOf(ctx.INTEGER().getText()));
+                enumNode.setValue(value);
                 break;
             }
             default:
                 throw new ParserException(
-                        constructListenerErrorMessage(INVALID_HOLDER, VALUE_DATA, ctx.INTEGER().getText(), ENTRY));
+                        constructListenerErrorMessage(INVALID_HOLDER, VALUE_DATA, ctx.value().getText(), ENTRY));
         }
     }
 
@@ -89,20 +93,22 @@
      *
      * @param listener Listener's object
      * @param ctx context object of the grammar rule
+     * @param value enum value
      * @return validation result
      */
-    private static boolean isEnumValueValid(TreeWalkListener listener, GeneratedYangParser.ValueStatementContext ctx) {
+    private static boolean isEnumValueValid(TreeWalkListener listener, GeneratedYangParser.ValueStatementContext ctx,
+            int value) {
         Parsable enumNode = listener.getParsedDataStack().pop();
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, VALUE_DATA, ctx.INTEGER().getText(), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, VALUE_DATA, ctx.value().getText(), ENTRY);
 
         Parsable tmpNode = listener.getParsedDataStack().peek();
         switch (tmpNode.getYangConstructType()) {
             case ENUMERATION_DATA: {
                 YangEnumeration yangEnumeration = (YangEnumeration) tmpNode;
                 for (YangEnum curEnum : yangEnumeration.getEnumSet()) {
-                    if (Integer.valueOf(ctx.INTEGER().getText()) == curEnum.getValue()) {
+                    if (value == curEnum.getValue()) {
                         listener.getParsedDataStack().push(enumNode);
                         return false;
                     }
@@ -113,7 +119,7 @@
             default:
                 listener.getParsedDataStack().push(enumNode);
                 throw new ParserException(
-                        constructListenerErrorMessage(INVALID_HOLDER, VALUE_DATA, ctx.INTEGER().getText(), ENTRY));
+                        constructListenerErrorMessage(INVALID_HOLDER, VALUE_DATA, ctx.value().getText(), ENTRY));
         }
     }
 }
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerUtil.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerUtil.java
index d5efe91..de11f05 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerUtil.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/parserutils/ListenerUtil.java
@@ -29,6 +29,18 @@
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.utils.YangConstructType;
 
+import static org.onosproject.yangutils.utils.UtilConstants.ADD;
+import static org.onosproject.yangutils.utils.UtilConstants.SPACE;
+import static org.onosproject.yangutils.utils.UtilConstants.SLASH;
+import static org.onosproject.yangutils.utils.UtilConstants.COLON;
+import static org.onosproject.yangutils.utils.UtilConstants.CARET;
+import static org.onosproject.yangutils.utils.UtilConstants.QUOTES;
+import static org.onosproject.yangutils.utils.UtilConstants.HYPHEN;
+import static org.onosproject.yangutils.utils.UtilConstants.EMPTY_STRING;
+import static org.onosproject.yangutils.utils.UtilConstants.TRUE;
+import static org.onosproject.yangutils.utils.UtilConstants.FALSE;
+import static org.onosproject.yangutils.utils.UtilConstants.YANG_FILE_ERROR;
+
 /**
  * Represents an utility for listener.
  */
@@ -37,18 +49,10 @@
     private static final Pattern IDENTIFIER_PATTERN = Pattern.compile("[a-zA-Z_][a-zA-Z0-9_.-]*");
     private static final String DATE_PATTERN = "[0-9]{4}-([0-9]{2}|[0-9])-([0-9]{2}|[0-9])";
     private static final String NON_NEGATIVE_INTEGER_PATTERN = "[0-9]+";
-    private static final String PLUS = "+";
+    private static final Pattern INTEGER_PATTERN = Pattern.compile("[-][0-9]+|[0-9]+");
     private static final String ONE = "1";
-    private static final String TRUE_KEYWORD = "true";
-    private static final String FALSE_KEYWORD = "false";
     private static final int IDENTIFIER_LENGTH = 64;
     private static final String DATE_FORMAT = "yyyy-MM-dd";
-    private static final String EMPTY_STRING = "";
-    private static final String HYPHEN = "-";
-    private static final String SLASH = "/";
-    private static final String SPACE = " ";
-    private static final String COLON = ":";
-    private static final String CARET = "^";
 
     /**
      * Creates a new listener util.
@@ -65,7 +69,7 @@
     public static String removeQuotesAndHandleConcat(String yangStringData) {
 
         yangStringData = yangStringData.replace("\"", EMPTY_STRING);
-        String[] tmpData = yangStringData.split(Pattern.quote(PLUS));
+        String[] tmpData = yangStringData.split(Pattern.quote(ADD));
         StringBuilder builder = new StringBuilder();
         for (String yangString : tmpData) {
             builder.append(yangString);
@@ -171,6 +175,41 @@
     }
 
     /**
+     * Validates integer value.
+     *
+     * @param integerValue integer to be validated
+     * @param yangConstruct yang construct for creating error message
+     * @param ctx context object of the grammar rule
+     * @return valid integer value
+     */
+    public static int getValidIntegerValue(String integerValue, YangConstructType yangConstruct,
+                                                      ParserRuleContext ctx) {
+
+        String value = removeQuotesAndHandleConcat(integerValue);
+        if (!INTEGER_PATTERN.matcher(value).matches()) {
+            ParserException parserException = new ParserException("YANG file error : " +
+                    YangConstructType.getYangConstructType(yangConstruct) + " value " + value + " is not " +
+                    "valid.");
+            parserException.setLine(ctx.getStart().getLine());
+            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+            throw parserException;
+        }
+
+        int valueInInteger;
+        try {
+            valueInInteger = Integer.parseInt(value);
+        } catch (NumberFormatException e) {
+            ParserException parserException = new ParserException("YANG file error : " +
+                    YangConstructType.getYangConstructType(yangConstruct) + " value " + value + " is not " +
+                    "valid.");
+            parserException.setLine(ctx.getStart().getLine());
+            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+            throw parserException;
+        }
+        return valueInInteger;
+    }
+
+    /**
      * Validates boolean value.
      *
      * @param booleanValue value to be validated
@@ -182,9 +221,9 @@
             ParserRuleContext ctx) {
 
         String value = removeQuotesAndHandleConcat(booleanValue);
-        if (value.equals(TRUE_KEYWORD)) {
+        if (value.equals(TRUE)) {
             return true;
-        } else if (value.equals(FALSE_KEYWORD)) {
+        } else if (value.equals(FALSE)) {
             return false;
         } else {
             ParserException parserException = new ParserException("YANG file error : " +
@@ -272,4 +311,21 @@
         }
         return targetNodes;
     }
+
+    /**
+     * Throws parser exception for unsupported YANG constructs.
+     *
+     * @param yangConstructType yang construct for creating error message
+     * @param ctx yang construct's context to get the line number and character position
+     * @param errorInfo error information
+     */
+    public static void handleUnsupportedYangConstruct(YangConstructType yangConstructType,
+        ParserRuleContext ctx, String errorInfo) {
+        ParserException parserException = new ParserException(YANG_FILE_ERROR
+                + QUOTES + YangConstructType.getYangConstructType(yangConstructType) + QUOTES
+                + errorInfo);
+        parserException.setLine(ctx.getStart().getLine());
+        parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+        throw parserException;
+    }
 }
\ No newline at end of file