diff --git a/utils/yangutils/src/main/resources/GeneratedYang.g4 b/utils/yangutils/src/main/resources/GeneratedYang.g4
new file mode 100644
index 0000000..c5dcf26
--- /dev/null
+++ b/utils/yangutils/src/main/resources/GeneratedYang.g4
@@ -0,0 +1,1226 @@
+/*
+ * 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.
+ */
+
+/**
+ * This is a YANG grammar for parser based on which ANTLR will generate YANG parser.
+ */
+
+grammar GeneratedYang;
+import YangLexer;
+
+@header {
+package org.onosproject.yangutils.parser.antlrgencode;
+}
+
+    yangfile : module_stmt
+             | submodule_stmt;
+
+    /**
+     * module-stmt         = optsep module-keyword sep identifier-arg-str
+     *                       optsep
+     *                       "{" stmtsep
+     *                           module-header-stmts
+     *                           linkage-stmts
+     *                           meta-stmts
+     *                           revision-stmts
+     *                           body-stmts
+     *                       "}" optsep
+     */
+
+    module_stmt : MODULE_KEYWORD IDENTIFIER LEFT_CURLY_BRACE module_body* RIGHT_CURLY_BRACE;
+
+    module_body : module_header_statement linkage_stmts meta_stmts revision_stmts body_stmts;
+
+    /**
+     * module-header-stmts = ;; these stmts can appear in any order
+     *                       [yang-version-stmt stmtsep]
+     *                        namespace-stmt stmtsep
+     *                        prefix-stmt stmtsep
+     */
+
+    module_header_statement : yang_version_stmt? namespace_stmt prefix_stmt
+                            | yang_version_stmt? prefix_stmt namespace_stmt
+                            | namespace_stmt yang_version_stmt? prefix_stmt
+                            | namespace_stmt prefix_stmt yang_version_stmt?
+                            | prefix_stmt namespace_stmt yang_version_stmt?
+                            | prefix_stmt yang_version_stmt? namespace_stmt?
+                            ;
+
+    /**
+     * linkage-stmts       = ;; these stmts can appear in any order
+     *                       *(import-stmt stmtsep)
+     *                       *(include-stmt stmtsep)
+     */
+
+    linkage_stmts : (import_stmt
+                  | include_stmt)*;
+
+    /**
+     * meta-stmts          = ;; these stmts can appear in any order
+     *                       [organization-stmt stmtsep]
+     *                       [contact-stmt stmtsep]
+     *                       [description-stmt stmtsep]
+     *                       [reference-stmt stmtsep]
+     */
+
+    meta_stmts : organization_stmt? contact_stmt? description_stmt? reference_stmt?
+               | organization_stmt? contact_stmt? reference_stmt? description_stmt?
+               | organization_stmt? description_stmt? contact_stmt? reference_stmt?
+               | organization_stmt? description_stmt? reference_stmt? contact_stmt?
+               | organization_stmt? reference_stmt? contact_stmt? description_stmt?
+               | organization_stmt? reference_stmt? description_stmt? contact_stmt?
+               | contact_stmt? organization_stmt? description_stmt? reference_stmt?
+               | contact_stmt? organization_stmt? reference_stmt? description_stmt?
+               | contact_stmt? reference_stmt? organization_stmt? description_stmt?
+               | contact_stmt? reference_stmt? description_stmt? organization_stmt?
+               | contact_stmt? description_stmt? reference_stmt? organization_stmt?
+               | contact_stmt? description_stmt? organization_stmt? reference_stmt?
+               | reference_stmt? contact_stmt? organization_stmt? description_stmt?
+               | reference_stmt? contact_stmt? description_stmt? organization_stmt?
+               | reference_stmt? organization_stmt? contact_stmt? description_stmt?
+               | reference_stmt? organization_stmt? description_stmt? contact_stmt?
+               | reference_stmt? description_stmt? organization_stmt? contact_stmt?
+               | reference_stmt? description_stmt? contact_stmt? organization_stmt?
+               | description_stmt? reference_stmt? contact_stmt? organization_stmt?
+               | description_stmt? reference_stmt? organization_stmt? contact_stmt?
+               | description_stmt? contact_stmt? reference_stmt? organization_stmt?
+               | description_stmt? contact_stmt? organization_stmt? reference_stmt?
+               | description_stmt? organization_stmt? contact_stmt? reference_stmt?
+               | description_stmt? organization_stmt? reference_stmt? contact_stmt?
+               ;
+
+    // revision-stmts      = *(revision-stmt stmtsep)
+    revision_stmts : revision_stmt*;
+
+    /**
+     * body-stmts          = *((extension-stmt /
+     *                          feature-stmt /
+     *                          identity-stmt /
+     *                          typedef-stmt /
+     *                          grouping-stmt /
+     *                          data-def-stmt /
+     *                          augment-stmt /
+     *                          rpc-stmt /
+     *                          notification-stmt /
+     *                          deviation-stmt) stmtsep)
+     */
+
+    body_stmts : (extension_stmt
+               | feature_stmt
+               | identity_stmt
+               | typedef_stmt
+               | grouping_stmt
+               | data_def_stmt
+               | augment_stmt
+               | rpc_stmt
+               | notification_stmt
+               | deviation_stmt)*
+               ;
+
+    /**
+     * yang-version-stmt   = yang-version-keyword sep yang-version-arg-str
+     *                       optsep stmtend
+     */
+
+    yang_version_stmt :   YANG_VERSION_KEYWORD INTEGER STMTEND;
+
+
+    /**
+     * namespace-stmt      = namespace-keyword sep uri-str optsep stmtend
+     * For namespace validation TODO in Listener
+     */
+    namespace_stmt : NAMESPACE_KEYWORD string STMTEND;
+
+    /**
+     * prefix-stmt         = prefix-keyword sep prefix-arg-str
+     *                       optsep stmtend
+     */
+    prefix_stmt : PREFIX_KEYWORD IDENTIFIER STMTEND;
+
+    /**
+     * import-stmt         = import-keyword sep identifier-arg-str optsep
+     *                       "{" stmtsep
+     *                           prefix-stmt stmtsep
+     *                           [revision-date-stmt stmtsep]
+     *                        "}"
+     */
+    import_stmt : IMPORT_KEYWORD IDENTIFIER LEFT_CURLY_BRACE import_stmt_body RIGHT_CURLY_BRACE;
+
+    import_stmt_body : prefix_stmt revision_date_stmt?;
+
+    // revision-date-stmt = revision-date-keyword sep revision-date stmtend
+    revision_date_stmt : REVISION_DATE_KEYWORD DATE_ARG STMTEND;
+
+    revision_date_stmt_body : revision_date_stmt;
+
+    /**
+     * include-stmt        = include-keyword sep identifier-arg-str optsep
+     *                             (";" /
+     *                              "{" stmtsep
+     *                                  [revision-date-stmt stmtsep]
+     *                            "}")
+     */
+    include_stmt : INCLUDE_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE revision_date_stmt_body? RIGHT_CURLY_BRACE);
+
+    /**
+     * organization-stmt   = organization-keyword sep string
+     *                            optsep stmtend
+     */
+    organization_stmt : ORGANIZATION_KEYWORD string STMTEND;
+
+    // contact-stmt        = contact-keyword sep string optsep stmtend
+    contact_stmt : CONTACT_KEYWORD string STMTEND;
+
+    // description-stmt    = description-keyword sep string optsep stmtend
+    description_stmt : DESCRIPTION_KEYWORD string STMTEND;
+
+    // reference-stmt      = reference-keyword sep string optsep stmtend
+    reference_stmt : REFERENCE_KEYWORD string STMTEND;
+
+    /**
+     * revision-stmt       = revision-keyword sep revision-date optsep
+     *                             (";" /
+     *                              "{" stmtsep
+     *                                  [description-stmt stmtsep]
+     *                                  [reference-stmt stmtsep]
+     *                              "}")
+     */
+    revision_stmt : REVISION_KEYWORD DATE_ARG (STMTEND | LEFT_CURLY_BRACE revision_stmt_body RIGHT_CURLY_BRACE);
+    revision_stmt_body : description_stmt? reference_stmt?;
+
+    /**
+     * submodule-stmt      = optsep submodule-keyword sep identifier-arg-str
+     *                             optsep
+     *                             "{" stmtsep
+     *                                 submodule-header-stmts
+     *                                 linkage-stmts
+     *                                 meta-stmts
+     *                                 revision-stmts
+     *                                 body-stmts
+     *                             "}" optsep
+     */
+    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;
+
+    /** submodule-header-stmts =
+     *                            ;; these stmts can appear in any order
+     *                            [yang-version-stmt stmtsep]
+     *                             belongs-to-stmt stmtsep
+     */
+    submodule_header_statement : yang_version_stmt? belongs_to_stmt
+                               | belongs_to_stmt yang_version_stmt?
+                              ;
+
+    /**
+     * belongs-to-stmt     = belongs-to-keyword sep identifier-arg-str
+     *                       optsep
+     *                       "{" stmtsep
+     *                           prefix-stmt stmtsep
+     *                       "}"
+     */
+    belongs_to_stmt : BELONGS_TO_KEYWORD IDENTIFIER LEFT_CURLY_BRACE belongs_to_stmt_body RIGHT_CURLY_BRACE;
+    belongs_to_stmt_body : prefix_stmt;
+
+    /**
+     * extension-stmt      = extension-keyword sep identifier-arg-str optsep
+     *                       (";" /
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [argument-stmt stmtsep]
+     *                            [status-stmt stmtsep]
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                        "}")
+     */
+    extension_stmt : EXTENSION_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE extension_body RIGHT_CURLY_BRACE);
+    extension_body : argument_stmt? status_stmt? description_stmt? reference_stmt?
+                   | argument_stmt? status_stmt? reference_stmt? description_stmt?
+                   | argument_stmt? description_stmt? status_stmt? reference_stmt?
+                   | argument_stmt? description_stmt? reference_stmt? status_stmt?
+                   | argument_stmt? reference_stmt? description_stmt? status_stmt?
+                   | argument_stmt? reference_stmt? status_stmt? description_stmt?
+                   | status_stmt? reference_stmt? argument_stmt? description_stmt?
+                   | status_stmt? reference_stmt? description_stmt? argument_stmt?
+                   | status_stmt? description_stmt? reference_stmt? argument_stmt?
+                   | status_stmt? description_stmt? argument_stmt? reference_stmt?
+                   | status_stmt? argument_stmt? reference_stmt? description_stmt?
+                   | status_stmt? argument_stmt? description_stmt? reference_stmt?
+                   | description_stmt? argument_stmt? status_stmt? reference_stmt?
+                   | description_stmt? argument_stmt? reference_stmt? status_stmt?
+                   | description_stmt? status_stmt? argument_stmt? reference_stmt?
+                   | description_stmt? status_stmt? reference_stmt? argument_stmt?
+                   | description_stmt? reference_stmt? status_stmt? argument_stmt?
+                   | description_stmt? reference_stmt? argument_stmt? status_stmt?
+                   | reference_stmt? description_stmt? argument_stmt? status_stmt?
+                   | reference_stmt? description_stmt? status_stmt? argument_stmt?
+                   | reference_stmt? status_stmt? argument_stmt? description_stmt?
+                   | reference_stmt? status_stmt? description_stmt? argument_stmt?
+                   | reference_stmt? argument_stmt? description_stmt? status_stmt?
+                   | reference_stmt? argument_stmt? status_stmt? description_stmt?
+                   ;
+
+    /**
+     * argument-stmt       = argument-keyword sep identifier-arg-str optsep
+     *                       (";" /
+     *                        "{" stmtsep
+     *                            [yin-element-stmt stmtsep]
+     *                        "}")
+     */
+    argument_stmt : ARGUMENT_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE argument_body RIGHT_CURLY_BRACE);
+    argument_body : yin_element_stmt?;
+
+    /**
+     * yin-element-stmt    = yin-element-keyword sep yin-element-arg-str
+     *                       stmtend
+     */
+    yin_element_stmt : YIN_ELEMENT_KEYWORD (TRUE_KEYWORD | FALSE_KEYWORD) STMTEND;
+
+    /**
+     * identity-stmt       = identity-keyword sep identifier-arg-str optsep
+     *                       (";" /
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [base-stmt stmtsep]
+     *                            [status-stmt stmtsep]
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                        "}")
+     */
+    identity_stmt : IDENTITY_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE identity_body RIGHT_CURLY_BRACE);
+    identity_body : base_stmt? status_stmt? description_stmt? reference_stmt?
+                  | base_stmt? status_stmt? reference_stmt? description_stmt?
+                  | base_stmt? description_stmt? status_stmt? reference_stmt?
+                  | base_stmt? description_stmt? reference_stmt? status_stmt?
+                  | base_stmt? reference_stmt? description_stmt? status_stmt?
+                  | base_stmt? reference_stmt? status_stmt? description_stmt?
+                  | reference_stmt? base_stmt? status_stmt? description_stmt?
+                  | reference_stmt? base_stmt? description_stmt? status_stmt?
+                  | reference_stmt? status_stmt? base_stmt? description_stmt?
+                  | reference_stmt? status_stmt? description_stmt? base_stmt?
+                  | reference_stmt? description_stmt? status_stmt? base_stmt?
+                  | reference_stmt? description_stmt? base_stmt? status_stmt?
+                  | description_stmt? reference_stmt? status_stmt? base_stmt?
+                  | description_stmt? reference_stmt? status_stmt? base_stmt?
+                  | description_stmt? reference_stmt? base_stmt? status_stmt?
+                  | description_stmt? status_stmt? base_stmt? reference_stmt?
+                  | description_stmt? status_stmt? reference_stmt? base_stmt?
+                  | description_stmt? base_stmt? reference_stmt? status_stmt?
+                  | description_stmt? base_stmt? status_stmt? reference_stmt?
+                  | status_stmt? base_stmt? description_stmt? reference_stmt?
+                  | status_stmt? base_stmt? reference_stmt? description_stmt?
+                  | status_stmt? description_stmt? base_stmt? reference_stmt?
+                  | status_stmt? description_stmt? reference_stmt? base_stmt?
+                  | status_stmt? reference_stmt? description_stmt? base_stmt?
+                  | status_stmt? reference_stmt? base_stmt? description_stmt?
+                  ;
+
+    /**
+     * base-stmt           = base-keyword sep identifier-ref-arg-str
+     *                          optsep stmtend*
+     * identifier-ref-arg  = [prefix ":"] identifier
+     */
+    base_stmt : BASE_KEYWORD string STMTEND;
+
+    /**
+     *  feature-stmt        = feature-keyword sep identifier-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             *(if-feature-stmt stmtsep)
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                         "}")
+     */
+    feature_stmt : FEATURE_KEYWORD string (STMTEND | LEFT_CURLY_BRACE feature_body RIGHT_CURLY_BRACE);
+    feature_body : if_feature_stmt* status_stmt? description_stmt? reference_stmt?
+                 | if_feature_stmt* status_stmt? reference_stmt? description_stmt?
+                 | if_feature_stmt* description_stmt? status_stmt? reference_stmt?
+                 | if_feature_stmt* description_stmt? reference_stmt? status_stmt?
+                 | if_feature_stmt* reference_stmt? status_stmt? description_stmt?
+                 | if_feature_stmt* reference_stmt? description_stmt? status_stmt?
+                 | status_stmt? if_feature_stmt* description_stmt? reference_stmt?
+                 | status_stmt? if_feature_stmt* reference_stmt? description_stmt?
+                 | status_stmt? description_stmt? if_feature_stmt* reference_stmt?
+                 | status_stmt? description_stmt? reference_stmt? if_feature_stmt*
+                 | status_stmt? reference_stmt? if_feature_stmt* description_stmt?
+                 | status_stmt? reference_stmt? description_stmt? if_feature_stmt*
+                 | description_stmt? if_feature_stmt* status_stmt? reference_stmt?
+                 | description_stmt? if_feature_stmt* reference_stmt? status_stmt?
+                 | description_stmt? status_stmt? if_feature_stmt* reference_stmt?
+                 | description_stmt? status_stmt? reference_stmt? if_feature_stmt*
+                 | description_stmt? reference_stmt* status_stmt? if_feature_stmt*
+                 | description_stmt? reference_stmt* if_feature_stmt? status_stmt?
+                 | reference_stmt? if_feature_stmt* status_stmt? description_stmt?
+                 | reference_stmt? if_feature_stmt* description_stmt? status_stmt?
+                 | reference_stmt? description_stmt? status_stmt? if_feature_stmt*
+                 | reference_stmt? description_stmt? if_feature_stmt* status_stmt?
+                 | reference_stmt? status_stmt? description_stmt? if_feature_stmt*
+                 | reference_stmt? status_stmt? if_feature_stmt* description_stmt?
+                 ;
+
+    /**
+     *  data-def-stmt       = container-stmt /
+     *                       leaf-stmt /
+     *                       leaf-list-stmt /
+     *                       list-stmt /
+     *                       choice-stmt /
+     *                       anyxml-stmt /
+     *                       uses-stmt
+     */
+    data_def_stmt : container_stmt
+                    | leaf_stmt
+                    | leaf_list_stmt
+                    | list_stmt
+                    | choice_stmt
+                    | uses_stmt;
+
+    /**
+     *  if-feature-stmt     = if-feature-keyword sep identifier-ref-arg-str
+     *                        optsep stmtend
+     */
+    if_feature_stmt : IF_FEATURE_KEYWORD string STMTEND;
+
+    /**
+    *    units-stmt          = units-keyword sep string optsep stmtend
+    */
+    units_stmt : UNITS_KEYWORD string STMTEND;
+
+    /**
+     *   typedef-stmt        = typedef-keyword sep identifier-arg-str optsep
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             type-stmt stmtsep
+     *                            [units-stmt stmtsep]
+     *                             [default-stmt stmtsep]
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                           "}"
+     * TODO : 0..1 occurance to be validated in listener
+     */
+    typedef_stmt : TYPEDEF_KEYWORD IDENTIFIER LEFT_CURLY_BRACE
+                   (type_stmt | units_stmt | default_stmt | status_stmt | description_stmt | reference_stmt)*
+                   RIGHT_CURLY_BRACE;
+
+    /**
+     *  type-stmt           = type-keyword sep identifier-ref-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                            type-body-stmts
+     *                         "}")
+     */
+    type_stmt : TYPE_KEYWORD string (STMTEND | LEFT_CURLY_BRACE type_body_stmts RIGHT_CURLY_BRACE);
+
+    /**
+     *  type-body-stmts     = numerical-restrictions /
+     *                        decimal64-specification /
+     *                       string-restrictions /
+     *                        enum-specification /
+     *                        leafref-specification /
+     *                        identityref-specification /
+     *                        instance-identifier-specification /
+     *                        bits-specification /
+     *                        union-specification
+     * TODO : decimal64-specification to be added
+     */
+    type_body_stmts : numerical_restrictions | string_restrictions | enum_specification
+                    | leafref_specification | identityref_specification | instance_identifier_specification
+                    | bits_specification | union_specification;
+
+    /**
+     *  numerical-restrictions = range-stmt stmtsep
+     */
+    numerical_restrictions : range_stmt;
+
+    /**
+     *  range-stmt          = range-keyword sep range-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [error-message-stmt stmtsep]
+     *                             [error-app-tag-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                          "}")
+     */
+    range_stmt : RANGE_KEYWORD string (STMTEND | LEFT_CURLY_BRACE common_stmts RIGHT_CURLY_BRACE);
+
+    common_stmts : error_message_stmt? error_app_tag_stmt? description_stmt? reference_stmt?
+                 | error_message_stmt? error_app_tag_stmt? reference_stmt? description_stmt?
+                 | error_message_stmt? description_stmt? error_app_tag_stmt? reference_stmt?
+                 | error_message_stmt? description_stmt? reference_stmt? error_app_tag_stmt?
+                 | error_message_stmt? reference_stmt? error_app_tag_stmt? description_stmt?
+                 | error_message_stmt? reference_stmt? description_stmt? error_app_tag_stmt?
+                 | error_app_tag_stmt? error_message_stmt? description_stmt? reference_stmt?
+                 | error_app_tag_stmt? error_message_stmt? reference_stmt? description_stmt?
+                 | error_app_tag_stmt? description_stmt? description_stmt? error_message_stmt?
+                 | error_app_tag_stmt? description_stmt? error_message_stmt? description_stmt?
+                 | error_app_tag_stmt? reference_stmt? error_message_stmt? description_stmt?
+                 | error_app_tag_stmt? reference_stmt? description_stmt? error_message_stmt?
+                 | description_stmt? error_message_stmt? error_app_tag_stmt? reference_stmt?
+                 | description_stmt? error_message_stmt? reference_stmt? error_app_tag_stmt?
+                 | description_stmt? error_app_tag_stmt? error_message_stmt? reference_stmt?
+                 | description_stmt? error_app_tag_stmt? reference_stmt? error_message_stmt?
+                 | description_stmt? reference_stmt? error_message_stmt? error_app_tag_stmt?
+                 | description_stmt? reference_stmt? error_app_tag_stmt? error_message_stmt?
+                 | reference_stmt? error_message_stmt? description_stmt? error_app_tag_stmt?
+                 | reference_stmt? error_message_stmt? error_app_tag_stmt? description_stmt?
+                 | reference_stmt? error_app_tag_stmt? description_stmt? error_message_stmt?
+                 | reference_stmt? error_app_tag_stmt? error_message_stmt? description_stmt?
+                 | reference_stmt? description_stmt? error_message_stmt? error_app_tag_stmt?
+                 | reference_stmt? description_stmt? error_app_tag_stmt? error_message_stmt?
+                 ;
+
+    /**
+     *  string-restrictions = ;; these stmts can appear in any order
+     *                        [length-stmt stmtsep]
+     *                        *(pattern-stmt stmtsep)
+     */
+    string_restrictions : ((length_stmt)? (pattern_stmt)*) | ((pattern_stmt)* (length_stmt)?);
+
+    /**
+     *  length-stmt         = length-keyword sep length-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [error-message-stmt stmtsep]
+     *                             [error-app-tag-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                          "}")
+     */
+    length_stmt : LENGTH_KEYWORD string
+                  (STMTEND | LEFT_CURLY_BRACE common_stmts RIGHT_CURLY_BRACE);
+
+    /**
+     *  pattern-stmt        = pattern-keyword sep string optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [error-message-stmt stmtsep]
+     *                             [error-app-tag-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                          "}")
+     */
+    pattern_stmt : PATTERN_KEYWORD string (STMTEND | LEFT_CURLY_BRACE common_stmts RIGHT_CURLY_BRACE);
+
+    /**
+     *  default-stmt        = default-keyword sep string stmtend
+     */
+    default_stmt : DEFAULT_KEYWORD string STMTEND;
+
+    /**
+     *  enum-specification  = 1*(enum-stmt stmtsep)
+     */
+    enum_specification : enum_stmt+;
+
+    /**
+     *  enum-stmt           = enum-keyword sep string optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [value-stmt stmtsep]
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                          "}")
+     */
+    enum_stmt : ENUM_KEYWORD string (STMTEND | LEFT_CURLY_BRACE enum_stmt_body RIGHT_CURLY_BRACE);
+
+    enum_stmt_body : value_stmt? status_stmt? description_stmt? reference_stmt?
+                   | value_stmt? status_stmt? reference_stmt? description_stmt?
+                   | value_stmt? description_stmt? status_stmt? reference_stmt?
+                   | value_stmt? description_stmt? reference_stmt? status_stmt?
+                   | value_stmt? reference_stmt? status_stmt? description_stmt?
+                   | value_stmt? reference_stmt? description_stmt? status_stmt?
+                   | status_stmt? value_stmt? description_stmt? reference_stmt?
+                   | status_stmt? value_stmt? reference_stmt? description_stmt?
+                   | status_stmt? description_stmt? description_stmt? value_stmt?
+                   | status_stmt? description_stmt? value_stmt? description_stmt?
+                   | status_stmt? reference_stmt? value_stmt? description_stmt?
+                   | status_stmt? reference_stmt? description_stmt? value_stmt?
+                   | description_stmt? value_stmt? status_stmt? reference_stmt?
+                   | description_stmt? value_stmt? reference_stmt? status_stmt?
+                   | description_stmt? status_stmt? value_stmt? reference_stmt?
+                   | description_stmt? status_stmt? reference_stmt? value_stmt?
+                   | description_stmt? reference_stmt? value_stmt? status_stmt?
+                   | description_stmt? reference_stmt? status_stmt? value_stmt?
+                   | reference_stmt? value_stmt? description_stmt? status_stmt?
+                   | reference_stmt? value_stmt? status_stmt? description_stmt?
+                   | reference_stmt? status_stmt? description_stmt? value_stmt?
+                   | reference_stmt? status_stmt? value_stmt? description_stmt?
+                   | reference_stmt? description_stmt? value_stmt? status_stmt?
+                   | reference_stmt? description_stmt? status_stmt? value_stmt?
+                   ;
+
+    /**
+     *  leafref-specification =
+     *                        ;; these stmts can appear in any order
+     *                        path-stmt stmtsep
+     *                        [require-instance-stmt stmtsep]
+     */
+    leafref_specification : (path_stmt (require_instance_stmt)?) | ((require_instance_stmt)? path_stmt);
+
+    /**
+     *  path-stmt           = path-keyword sep path-arg-str stmtend
+     */
+    path_stmt : PATH_KEYWORD string STMTEND;
+
+    /**
+     *  require-instance-stmt = require-instance-keyword sep
+     *                           require-instance-arg-str stmtend
+     *  require-instance-arg-str = < a string that matches the rule
+     *                             require-instance-arg >
+     *  require-instance-arg = true-keyword / false-keyword
+     */
+    require_instance_stmt : REQUIRE_INSTANCE_KEYWORD (TRUE_KEYWORD | FALSE_KEYWORD) STMTEND;
+
+    /**
+     *  instance-identifier-specification =
+     *                        [require-instance-stmt stmtsep]
+     */
+    instance_identifier_specification : require_instance_stmt?;
+
+    /**
+     * identityref-specification =
+     *                        base-stmt stmtsep
+     */
+    identityref_specification : base_stmt;
+
+    /**
+     *  union-specification = 1*(type-stmt stmtsep)
+     */
+    union_specification : type_stmt+;
+
+    /**
+     *  bits-specification  = 1*(bit-stmt stmtsep)
+     */
+    bits_specification : bit_stmt+;
+
+    /**
+     * bit-stmt            = bit-keyword sep identifier-arg-str optsep
+     *                       (";" /
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [position-stmt stmtsep]
+     *                            [status-stmt stmtsep]
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                          "}"
+     *                        "}")
+     */
+    bit_stmt : BIT_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE bit_body_stmt RIGHT_CURLY_BRACE);
+
+    bit_body_stmt : position_stmt? status_stmt? description_stmt? reference_stmt?
+                  | position_stmt? status_stmt? reference_stmt? description_stmt?
+                  | position_stmt? description_stmt? status_stmt? reference_stmt?
+                  | position_stmt? description_stmt? reference_stmt? status_stmt?
+                  | position_stmt? reference_stmt? status_stmt? description_stmt?
+                  | position_stmt? reference_stmt? description_stmt? status_stmt?
+                  | status_stmt? position_stmt? description_stmt? reference_stmt?
+                  | status_stmt? position_stmt? reference_stmt? description_stmt?
+                  | status_stmt? description_stmt? description_stmt? position_stmt?
+                  | status_stmt? description_stmt? position_stmt? description_stmt?
+                  | status_stmt? reference_stmt? position_stmt? description_stmt?
+                  | status_stmt? reference_stmt? description_stmt? position_stmt?
+                  | description_stmt? position_stmt? status_stmt? reference_stmt?
+                  | description_stmt? position_stmt? reference_stmt? status_stmt?
+                  | description_stmt? status_stmt? position_stmt? reference_stmt?
+                  | description_stmt? status_stmt? reference_stmt? position_stmt?
+                  | description_stmt? reference_stmt? position_stmt? status_stmt?
+                  | description_stmt? reference_stmt? status_stmt? position_stmt?
+                  | reference_stmt? position_stmt? description_stmt? status_stmt?
+                  | reference_stmt? position_stmt? status_stmt? description_stmt?
+                  | reference_stmt? status_stmt? description_stmt? position_stmt?
+                  | reference_stmt? status_stmt? position_stmt? description_stmt?
+                  | reference_stmt? description_stmt? position_stmt? status_stmt?
+                  | reference_stmt? description_stmt? status_stmt? position_stmt?
+                  ;
+
+    /**
+     *  position-stmt       = position-keyword sep
+     *                        position-value-arg-str stmtend
+     *  position-value-arg-str = < a string that matches the rule
+     *                              position-value-arg >
+     *  position-value-arg  = non-negative-integer-value
+     */
+    position_stmt : POSITION_KEYWORD INTEGER STMTEND;
+
+    /**
+     *  status-stmt         = status-keyword sep status-arg-str stmtend
+     *  status-arg-str      = < a string that matches the rule
+     *                         status-arg >
+     *  status-arg          = current-keyword /
+     *                        obsolete-keyword /
+     *                        deprecated-keyword
+     */
+    status_stmt : STATUS_KEYWORD (CURRENT_KEYWORD | OBSOLETE_KEYWORD | DEPRECATED_KEYWORD) STMTEND;
+
+    /**
+     *  config-stmt         = config-keyword sep
+     *                        config-arg-str stmtend
+     *  config-arg-str      = < a string that matches the rule
+     *                          config-arg >
+     *  config-arg          = true-keyword / false-keyword
+     */
+    config_stmt : CONFIG_KEYWORD (TRUE_KEYWORD | FALSE_KEYWORD) STMTEND;
+
+    /**
+     *  mandatory-stmt      = mandatory-keyword sep
+     *                        mandatory-arg-str stmtend
+     * 
+     *  mandatory-arg-str   = < a string that matches the rule
+     *                          mandatory-arg >
+     * 
+     *  mandatory-arg       = true-keyword / false-keyword 
+     */
+    mandatory_stmt : MANDATORY_KEYWORD (TRUE_KEYWORD | FALSE_KEYWORD) STMTEND;
+
+    /**
+     *  presence-stmt       = presence-keyword sep string stmtend
+     */
+    presence_stmt : PRESENCE_KEYWORD string STMTEND;
+
+    /**
+     *  ordered-by-stmt     = ordered-by-keyword sep
+     *                        ordered-by-arg-str stmtend
+     * 
+     *  ordered-by-arg-str  = < a string that matches the rule
+     *                          ordered-by-arg >
+     * 
+     *  ordered-by-arg      = user-keyword / system-keyword
+     */
+    ordered_by_stmt : ORDERED_BY_KEYWORD (USER_KEYWORD | SYSTEM_KEYWORD) STMTEND;
+
+    /**
+     *  must-stmt           = must-keyword sep string optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [error-message-stmt stmtsep]
+     *                             [error-app-tag-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                          "}")
+     */
+    must_stmt : MUST_KEYWORD string (STMTEND | LEFT_CURLY_BRACE common_stmts RIGHT_CURLY_BRACE);
+
+    /**
+     *   error-message-stmt  = error-message-keyword sep string stmtend
+     */
+    error_message_stmt : ERROR_MESSAGE_KEYWORD string STMTEND;
+
+    /**
+     *  error-app-tag-stmt  = error-app-tag-keyword sep string stmtend
+     */
+    error_app_tag_stmt : ERROR_APP_TAG_KEYWORD string STMTEND;
+
+    /**
+     *  min-elements-stmt   = min-elements-keyword sep
+     *                        min-value-arg-str stmtend
+     *  min-value-arg-str   = < a string that matches the rule
+     *                          min-value-arg >
+     *  min-value-arg       = non-negative-integer-value
+     */
+    min_elements_stmt : MIN_ELEMENTS_KEYWORD INTEGER STMTEND;
+
+    /**
+     *  max-elements-stmt   = max-elements-keyword sep
+     *                        max-value-arg-str stmtend
+     *  max-value-arg-str   = < a string that matches the rule
+     *                          max-value-arg >
+     
+     */
+    max_elements_stmt :  MAX_ELEMENTS_KEYWORD max_value_arg STMTEND;
+
+    /**
+     *  max-value-arg       = unbounded-keyword /
+     *                        positive-integer-value
+     */
+    max_value_arg : UNBOUNDED_KEYWORD | INTEGER;
+
+    /**
+     *  value-stmt          = value-keyword sep integer-value stmtend
+     */
+    value_stmt : VALUE_KEYWORD ((MINUS INTEGER) | INTEGER) STMTEND;
+
+    /**
+     *   grouping-stmt       = grouping-keyword sep identifier-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                             *((typedef-stmt /
+     *                                grouping-stmt) stmtsep)
+     *                             *(data-def-stmt stmtsep)
+     *                         "}")
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    grouping_stmt : GROUPING_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE
+                      (status_stmt | description_stmt | reference_stmt | typedef_stmt | grouping_stmt
+                       | data_def_stmt)* RIGHT_CURLY_BRACE);
+
+    /**
+     *  container-stmt      = container-keyword sep identifier-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [when-stmt stmtsep]
+     *                             *(if-feature-stmt stmtsep)
+     *                             *(must-stmt stmtsep)
+     *                             [presence-stmt stmtsep]
+     *                             [config-stmt stmtsep]
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                             *((typedef-stmt /
+     *                                grouping-stmt) stmtsep)
+     *                             *(data-def-stmt stmtsep)
+     *                         "}")
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    container_stmt : CONTAINER_KEYWORD IDENTIFIER
+                     (STMTEND | LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | must_stmt | presence_stmt | config_stmt
+                     | status_stmt | description_stmt | reference_stmt | typedef_stmt | grouping_stmt
+                     | data_def_stmt)* RIGHT_CURLY_BRACE);
+
+    /**
+     *  leaf-stmt           = leaf-keyword sep identifier-arg-str optsep
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [when-stmt stmtsep]
+     *                            *(if-feature-stmt stmtsep)
+     *                            type-stmt stmtsep
+     *                            [units-stmt stmtsep]
+     *                            *(must-stmt stmtsep)
+     *                            [default-stmt stmtsep]
+     *                            [config-stmt stmtsep]
+     *                            [mandatory-stmt stmtsep]
+     *                            [status-stmt stmtsep]
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                         "}"
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    leaf_stmt : LEAF_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | type_stmt | units_stmt
+              | must_stmt | default_stmt | config_stmt | mandatory_stmt | status_stmt  | description_stmt
+              | reference_stmt)* RIGHT_CURLY_BRACE;
+
+    /**
+     *  leaf-list-stmt      = leaf-list-keyword sep identifier-arg-str optsep
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [when-stmt stmtsep]
+     *                            *(if-feature-stmt stmtsep)
+     *                            type-stmt stmtsep
+     *                            [units-stmt stmtsep]
+     *                            *(must-stmt stmtsep)
+     *                            [config-stmt stmtsep]
+     *                            [min-elements-stmt stmtsep]
+     *                            [max-elements-stmt stmtsep]
+     *                            [ordered-by-stmt stmtsep]
+     *                            [status-stmt stmtsep]
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                         "}"
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    leaf_list_stmt : LEAF_LIST_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | type_stmt
+                     | units_stmt | must_stmt | config_stmt | min_elements_stmt | max_elements_stmt | ordered_by_stmt
+                     | status_stmt | description_stmt | reference_stmt)* RIGHT_CURLY_BRACE;
+
+    /**
+     *  list-stmt           = list-keyword sep identifier-arg-str optsep
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [when-stmt stmtsep]
+     *                            *(if-feature-stmt stmtsep)
+     *                            *(must-stmt stmtsep)
+     *                            [key-stmt stmtsep]
+     *                            *(unique-stmt stmtsep)
+     *                            [config-stmt stmtsep]
+     *                            [min-elements-stmt stmtsep]
+     *                            [max-elements-stmt stmtsep]
+     *                            [ordered-by-stmt stmtsep]
+     *                            [status-stmt stmtsep]
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                            *((typedef-stmt /
+     *                               grouping-stmt) stmtsep)
+     *                            1*(data-def-stmt stmtsep)
+     *                         "}"
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    list_stmt : LIST_KEYWORD IDENTIFIER LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | must_stmt | key_stmt
+              | unique_stmt | config_stmt | min_elements_stmt | max_elements_stmt | ordered_by_stmt | status_stmt
+              | description_stmt | reference_stmt | typedef_stmt | grouping_stmt| data_def_stmt)* RIGHT_CURLY_BRACE;
+
+    /**
+     *  key-stmt            = key-keyword sep key-arg-str stmtend
+     */
+    key_stmt : KEY_KEYWORD string STMTEND;
+
+    /**
+     *  unique-stmt         = unique-keyword sep unique-arg-str stmtend
+     */
+    unique_stmt: UNIQUE_KEYWORD string STMTEND;
+
+    /**
+     *  choice-stmt         = choice-keyword sep identifier-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [when-stmt stmtsep]
+     *                             *(if-feature-stmt stmtsep)
+     *                             [default-stmt stmtsep]
+     *                             [config-stmt stmtsep]
+     *                             [mandatory-stmt stmtsep]
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                             *((short-case-stmt / case-stmt) stmtsep)
+     *                         "}")
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    choice_stmt : CHOICE_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | default_stmt
+                  | config_stmt | mandatory_stmt | status_stmt | description_stmt | reference_stmt | short_case_stmt
+                  | case_stmt)* RIGHT_CURLY_BRACE);
+
+    /**
+     *  short-case-stmt     = container-stmt /
+     *                        leaf-stmt /
+     *                        leaf-list-stmt /
+     *                        list-stmt /
+     *                        anyxml-stmt
+     */
+    short_case_stmt : container_stmt | leaf_stmt | leaf_list_stmt | list_stmt;
+
+    /**
+     *  case-stmt           = case-keyword sep identifier-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [when-stmt stmtsep]
+     *                             *(if-feature-stmt stmtsep)
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                             *(data-def-stmt stmtsep)
+     *                         "}")
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    case_stmt : CASE_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | status_stmt
+              | description_stmt | reference_stmt | data_def_stmt)* RIGHT_CURLY_BRACE);
+
+    /**
+     *  uses-stmt           = uses-keyword sep identifier-ref-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [when-stmt stmtsep]
+     *                             *(if-feature-stmt stmtsep)
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                             *(refine-stmt stmtsep)
+     *                             *(uses-augment-stmt stmtsep)
+     *                         "}")
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    uses_stmt : USES_KEYWORD string (STMTEND | LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | status_stmt
+                | description_stmt | reference_stmt | refine_stmt | uses_augment_stmt)* RIGHT_CURLY_BRACE);
+
+    /**
+     *  refine-stmt         = refine-keyword sep refine-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             (refine-container-stmts /
+     *                              refine-leaf-stmts /
+     *                              refine-leaf-list-stmts /
+     *                              refine-list-stmts /
+     *                              refine-choice-stmts /
+     *                              refine-case-stmts /
+     *                              refine-anyxml-stmts)
+     *                         "}")
+     */
+    refine_stmt : REFINE_KEYWORD string (STMTEND  | LEFT_CURLY_BRACE (refine_container_stmts | refine_leaf_stmts
+                  | refine_leaf_list_stmts | refine_list_stmts | refine_choice_stmts | refine_case_stmts)
+                  RIGHT_CURLY_BRACE);
+
+    /**
+     *  refine-container-stmts =
+     *                        ;; these stmts can appear in any order
+     *                        *(must-stmt stmtsep)
+     *                        [presence-stmt stmtsep]
+     *                        [config-stmt stmtsep]
+     *                        [description-stmt stmtsep]
+     *                         [reference-stmt stmtsep]
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    refine_container_stmts : (must_stmt | presence_stmt | config_stmt | description_stmt | reference_stmt)* ;
+
+    /**
+     *   refine-leaf-stmts   = ;; these stmts can appear in any order
+     *                         *(must-stmt stmtsep)
+     *                         [default-stmt stmtsep]
+     *                         [config-stmt stmtsep]
+     *                        [mandatory-stmt stmtsep]
+     *                        [description-stmt stmtsep]
+     *                        [reference-stmt stmtsep]
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    refine_leaf_stmts : (must_stmt | default_stmt | config_stmt | mandatory_stmt | description_stmt | reference_stmt)*;
+
+    /**
+     *  refine-leaf-list-stmts =
+     *                        ;; these stmts can appear in any order
+     *                        *(must-stmt stmtsep)
+     *                        [config-stmt stmtsep]
+     *                        [min-elements-stmt stmtsep]
+     *                        [max-elements-stmt stmtsep]
+     *                        [description-stmt stmtsep]
+     *                        [reference-stmt stmtsep]
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    refine_leaf_list_stmts : (must_stmt | config_stmt | min_elements_stmt | max_elements_stmt | description_stmt
+                             | reference_stmt)*;
+
+    /**
+     *  refine-list-stmts   = ;; these stmts can appear in any order
+     *                        *(must-stmt stmtsep)
+     *                        [config-stmt stmtsep]
+     *                        [min-elements-stmt stmtsep]
+     *                        [max-elements-stmt stmtsep]
+     *                        [description-stmt stmtsep]
+     *                        [reference-stmt stmtsep]
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    refine_list_stmts : (must_stmt | config_stmt | min_elements_stmt | max_elements_stmt | description_stmt
+                        | reference_stmt)*;
+
+    /**
+     *  refine-choice-stmts = ;; these stmts can appear in any order
+     *                        [default-stmt stmtsep]
+     *                        [config-stmt stmtsep]
+     *                        [mandatory-stmt stmtsep]
+     *                        [description-stmt stmtsep]
+     *                        [reference-stmt stmtsep]
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    refine_choice_stmts : (default_stmt | config_stmt | mandatory_stmt | description_stmt | reference_stmt)*;
+
+    /**
+     *  refine-case-stmts   = ;; these stmts can appear in any order
+     *                        [description-stmt stmtsep]
+     *                        [reference-stmt stmtsep]
+     *
+     */
+    refine_case_stmts : (description_stmt | reference_stmt)? | (reference_stmt | description_stmt)?;
+
+    /**
+     *  uses-augment-stmt   = augment-keyword sep uses-augment-arg-str optsep
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [when-stmt stmtsep]
+     *                            *(if-feature-stmt stmtsep)
+     *                            [status-stmt stmtsep]
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                            1*((data-def-stmt stmtsep) /
+     *                               (case-stmt stmtsep))
+     *                         "}"
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    uses_augment_stmt : AUGMENT_KEYWORD string LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | status_stmt
+                        | description_stmt | reference_stmt | data_def_stmt | case_stmt)* RIGHT_CURLY_BRACE;
+
+    /**
+     *  augment-stmt        = augment-keyword sep augment-arg-str optsep
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [when-stmt stmtsep]
+     *                            *(if-feature-stmt stmtsep)
+     *                            [status-stmt stmtsep]
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                            1*((data-def-stmt stmtsep) /
+     *                               (case-stmt stmtsep))
+     *                         "}"
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    augment_stmt : AUGMENT_KEYWORD string LEFT_CURLY_BRACE (when_stmt | if_feature_stmt | status_stmt
+                   | description_stmt | reference_stmt | data_def_stmt  | case_stmt)* RIGHT_CURLY_BRACE;
+
+    /**
+     *  when-stmt           = when-keyword sep string optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                          "}")
+     *
+     */
+    when_stmt : WHEN_KEYWORD string (STMTEND | LEFT_CURLY_BRACE ((description_stmt? reference_stmt?)
+                       | (reference_stmt? description_stmt?)) RIGHT_CURLY_BRACE);
+
+    /**
+     *  rpc-stmt            = rpc-keyword sep identifier-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             *(if-feature-stmt stmtsep)
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                             *((typedef-stmt /
+     *                                grouping-stmt) stmtsep)
+     *                             [input-stmt stmtsep]
+     *                             [output-stmt stmtsep]
+     *                         "}")
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    rpc_stmt : RPC_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE (if_feature_stmt | status_stmt | description_stmt
+                | reference_stmt | typedef_stmt | grouping_stmt | input_stmt | output_stmt)* RIGHT_CURLY_BRACE);
+
+    /**
+     * input-stmt          = input-keyword optsep
+     *                       "{" stmtsep
+     *                           ;; these stmts can appear in any order
+     *                           *((typedef-stmt /
+     *                              grouping-stmt) stmtsep)
+     *                           1*(data-def-stmt stmtsep)
+     *                         "}"
+     */
+    input_stmt : INPUT_KEYWORD LEFT_CURLY_BRACE
+                 ((typedef_stmt | grouping_stmt)* | data_def_stmt+)
+                 | (data_def_stmt+ | (typedef_stmt | grouping_stmt)*)RIGHT_CURLY_BRACE;
+
+    /**
+     *  output-stmt         = output-keyword optsep
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            *((typedef-stmt /
+     *                               grouping-stmt) stmtsep)
+     *                            1*(data-def-stmt stmtsep)
+     *                        "}"
+     */
+    output_stmt : OUTPUT_KEYWORD LEFT_CURLY_BRACE
+                 ((typedef_stmt | grouping_stmt)* | data_def_stmt+)
+                 | (data_def_stmt+ | (typedef_stmt | grouping_stmt)*)RIGHT_CURLY_BRACE;
+
+    /**
+     *  notification-stmt   = notification-keyword sep
+     *                        identifier-arg-str optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             ;; these stmts can appear in any order
+     *                             *(if-feature-stmt stmtsep)
+     *                             [status-stmt stmtsep]
+     *                             [description-stmt stmtsep]
+     *                             [reference-stmt stmtsep]
+     *                             *((typedef-stmt /
+     *                                grouping-stmt) stmtsep)
+     *                             *(data-def-stmt stmtsep)
+     *                         "}")
+     * TODO : 0..1 occurance to be checked in listener
+     */
+     notification_stmt : NOTIFICATION_KEYWORD IDENTIFIER (STMTEND | LEFT_CURLY_BRACE (if_feature_stmt | status_stmt
+                        | description_stmt | reference_stmt | typedef_stmt | grouping_stmt | data_def_stmt)*
+                        RIGHT_CURLY_BRACE);
+
+    /**
+     *  deviation-stmt      = deviation-keyword sep
+     *                        deviation-arg-str optsep
+     *                        "{" stmtsep
+     *                            ;; these stmts can appear in any order
+     *                            [description-stmt stmtsep]
+     *                            [reference-stmt stmtsep]
+     *                            (deviate-not-supported-stmt /
+     *                              1*(deviate-add-stmt /
+     *                                 deviate-replace-stmt /
+     *                                 deviate-delete-stmt))
+     *                        "}"
+     * TODO : 0..1 occurance to be checked in listener
+     */
+    deviation_stmt: DEVIATION_KEYWORD string LEFT_CURLY_BRACE (description_stmt | reference_stmt
+                    | deviate_not_supported_stmt | deviate_add_stmt | deviate_replace_stmt | deviate_delete_stmt)*
+                    RIGHT_CURLY_BRACE;
+
+    /**
+     * deviate-not-supported-stmt =
+     *                       deviate-keyword sep
+     *                       not-supported-keyword optsep
+     *                       (";" /
+     *                        "{" stmtsep
+     *                        "}")
+     */
+    deviate_not_supported_stmt: DEVIATE_KEYWORD NOT_SUPPORTED_KEYWORD (STMTEND | LEFT_CURLY_BRACE RIGHT_CURLY_BRACE);
+
+    /**
+     *  deviate-add-stmt    = deviate-keyword sep add-keyword optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             [units-stmt stmtsep]
+     *                             *(must-stmt stmtsep)
+     *                             *(unique-stmt stmtsep)
+     *                             [default-stmt stmtsep]
+     *                             [config-stmt stmtsep]
+     *                             [mandatory-stmt stmtsep]
+     *                             [min-elements-stmt stmtsep]
+     *                             [max-elements-stmt stmtsep]
+     *                         "}")
+     */
+    deviate_add_stmt: DEVIATE_KEYWORD ADD_KEYWORD (STMTEND | (LEFT_CURLY_BRACE units_stmt? must_stmt* unique_stmt*
+                      default_stmt? config_stmt? mandatory_stmt? min_elements_stmt? max_elements_stmt?
+                      RIGHT_CURLY_BRACE));
+
+    /**
+     *  deviate-delete-stmt = deviate-keyword sep delete-keyword optsep
+     *                        (";" /
+     *                         "{" stmtsep
+     *                             [units-stmt stmtsep]
+     *                             *(must-stmt stmtsep)
+     *                             *(unique-stmt stmtsep)
+     *                               [default-stmt stmtsep]
+     *                           "}")
+     */
+    deviate_delete_stmt: DEVIATE_KEYWORD DELETE_KEYWORD (STMTEND
+                       | (LEFT_CURLY_BRACE  units_stmt? must_stmt* unique_stmt* default_stmt? RIGHT_CURLY_BRACE));
+
+    /** 
+     *   deviate-replace-stmt = deviate-keyword sep replace-keyword optsep
+     *                         (";" /
+     *                          "{" stmtsep
+     *                              [type-stmt stmtsep]
+     *                              [units-stmt stmtsep]
+     *                              [default-stmt stmtsep]
+     *                              [config-stmt stmtsep]
+     *                              [mandatory-stmt stmtsep]
+     *                              [min-elements-stmt stmtsep]
+     *                              [max-elements-stmt stmtsep]
+     *                          "}")
+     */
+    deviate_replace_stmt: DEVIATE_KEYWORD REPLACE_KEYWORD (STMTEND | (LEFT_CURLY_BRACE type_stmt? units_stmt?
+                           default_stmt? config_stmt? mandatory_stmt? min_elements_stmt?
+                           max_elements_stmt? RIGHT_CURLY_BRACE));
+
+    string : STRING (PLUS STRING)*;
+
diff --git a/utils/yangutils/src/main/resources/YangLexer.g4 b/utils/yangutils/src/main/resources/YangLexer.g4
new file mode 100644
index 0000000..12bb19b
--- /dev/null
+++ b/utils/yangutils/src/main/resources/YangLexer.g4
@@ -0,0 +1,137 @@
+/*
+ * 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.
+ */
+
+/**
+ * This is a YANG grammar for lexer based on which ANTLR will generate YANG lexer.
+ */
+
+lexer grammar YangLexer;
+
+    // Statements keywords
+    ANYXML_KEYWORD      : 'anyxml';
+    ARGUMENT_KEYWORD    : 'argument';
+    AUGMENT_KEYWORD     : 'augment';
+    BASE_KEYWORD        : 'base';
+    BELONGS_TO_KEYWORD  : 'belongs-to';
+    BIT_KEYWORD         : 'bit';
+    CASE_KEYWORD        : 'case';
+    CHOICE_KEYWORD      : 'choice';
+    CONFIG_KEYWORD      : 'config';
+    CONTACT_KEYWORD     : 'contact';
+    CONTAINER_KEYWORD   : 'container';
+    DEFAULT_KEYWORD     : 'default';
+    DESCRIPTION_KEYWORD : 'description';
+    ENUM_KEYWORD        : 'enum';
+    ERROR_APP_TAG_KEYWORD : 'error-app-tag';
+    ERROR_MESSAGE_KEYWORD : 'error-message';
+    EXTENSION_KEYWORD   : 'extension';
+    DEVIATION_KEYWORD   : 'deviation';
+    DEVIATE_KEYWORD     : 'deviate';
+    FEATURE_KEYWORD     : 'feature';
+    FRACTION_DIGITS_KEYWORD : 'fraction-digits';
+    GROUPING_KEYWORD    : 'grouping';
+    IDENTITY_KEYWORD    : 'identity';
+    IF_FEATURE_KEYWORD  : 'if-feature';
+    IMPORT_KEYWORD      : 'import';
+    INCLUDE_KEYWORD     : 'include';
+    INPUT_KEYWORD       : 'input';
+    KEY_KEYWORD         : 'key';
+    LEAF_KEYWORD        : 'leaf';
+    LEAF_LIST_KEYWORD   : 'leaf-list';
+    LENGTH_KEYWORD      : 'length';
+    LIST_KEYWORD        : 'list';
+    MANDATORY_KEYWORD   : 'mandatory';
+    MAX_ELEMENTS_KEYWORD : 'max-elements';
+    MIN_ELEMENTS_KEYWORD : 'min-elements';
+    MODULE_KEYWORD      : 'module';
+    MUST_KEYWORD        : 'must';
+    NAMESPACE_KEYWORD   : 'namespace';
+    NOTIFICATION_KEYWORD: 'notification';
+    ORDERED_BY_KEYWORD  : 'ordered-by';
+    ORGANIZATION_KEYWORD: 'organization';
+    OUTPUT_KEYWORD      : 'output';
+    PATH_KEYWORD        : 'path';
+    PATTERN_KEYWORD     : 'pattern';
+    POSITION_KEYWORD    : 'position';
+    PREFIX_KEYWORD      : 'prefix';
+    PRESENCE_KEYWORD    : 'presence';
+    RANGE_KEYWORD       : 'range';
+    REFERENCE_KEYWORD   : 'reference';
+    REFINE_KEYWORD      : 'refine';
+    REQUIRE_INSTANCE_KEYWORD : 'require-instance';
+    REVISION_KEYWORD    : 'revision';
+    REVISION_DATE_KEYWORD : 'revision-date';
+    RPC_KEYWORD         : 'rpc';
+    STATUS_KEYWORD      : 'status';
+    SUBMODULE_KEYWORD   : 'submodule';
+    TYPE_KEYWORD        : 'type';
+    TYPEDEF_KEYWORD     : 'typedef';
+    UNIQUE_KEYWORD      : 'unique';
+    UNITS_KEYWORD       : 'units';
+    USES_KEYWORD        : 'uses';
+    VALUE_KEYWORD       : 'value';
+    WHEN_KEYWORD        : 'when';
+    YANG_VERSION_KEYWORD: 'yang-version';
+    YIN_ELEMENT_KEYWORD : 'yin-element';
+    ADD_KEYWORD         : 'add';
+    CURRENT_KEYWORD     : 'current';
+    DELETE_KEYWORD      : 'delete';
+    DEPRECATED_KEYWORD  : 'deprecated';
+    FALSE_KEYWORD       : 'false';
+    MAX_KEYWORD         : 'max';
+    MIN_KEYWORD         : 'min';
+    NOT_SUPPORTED_KEYWORD : 'not-supported';
+    OBSOLETE_KEYWORD    : 'obsolete';
+    REPLACE_KEYWORD     : 'replace';
+    SYSTEM_KEYWORD      : 'system';
+    TRUE_KEYWORD        : 'true';
+    UNBOUNDED_KEYWORD   : 'unbounded';
+    USER_KEYWORD        : 'user';
+
+    // Lexer tokens to be skipped
+    COMMENT
+        :   '/*' .*? '*/'    -> channel(HIDDEN)
+        ;
+    WS  :   [ \r\t\u000C\n]+ -> channel(HIDDEN)
+        ;
+    LINE_COMMENT
+        : '//' ~[\r\n]* '\r'? '\n' -> channel(HIDDEN)
+        ;
+
+    // Additional rules
+    INTEGER             : DIGIT+;
+    DATE_ARG            : DIGIT DIGIT DIGIT DIGIT '-' DIGIT DIGIT '-' DIGIT DIGIT;
+    LEFT_CURLY_BRACE    : '{';
+    RIGHT_CURLY_BRACE   : '}';
+    IDENTIFIER          : (ALPHA | '_')
+                          (ALPHA | DIGIT | '_' | '-' | '.')*;
+    STMTEND             : ';';
+    DQUOTE              : '"';
+    COLON               : ':';
+    PLUS : '+';
+    MINUS: '-';
+
+    STRING : ((~( '\r' | '\n' | '\t' | ' ' | ';' | '{' | '"' | '\'')~( '\r' | '\n' | '\t' | ' ' | ';' | '{' )* ) | SUB_STRING );
+
+    //Fragment rules
+    fragment SUB_STRING : ('"' (ESC | ~["])*'"') | ('\'' (ESC | ~['])*'\'') ;
+    fragment ESC :  '\\' (["\\/bfnrt] | UNICODE) ;
+    fragment UNICODE : 'u' HEX HEX HEX HEX ;
+    fragment HEX : [0-9a-fA-F] ;
+    fragment ALPHA      : [A-Za-z];
+    fragment DIGIT      : [0-9];
+    fragment URN        : [u][r][n];
+    fragment HTTP       : [h][t][t][p];
\ No newline at end of file