[ONOS-4650][ONOS-4726][ONOS-4727] [ONOS-4728]Implement must parser + when parser…

… + feature + if-feature + revision defect fix

Change-Id: I0a3aee6c1c6b72ef7da7f7f565fd0f149fe3fd42

@@ -29,5 +29,10 @@ public enum ResolvableType {
     /**
     /**
      * Identifies the uses.
      * Identifies the uses.
      */
      */
-    YANG_USES
+    YANG_USES,
+
+    /**
+     * Identifies the if-feature.
+     */
+    YANG_IF_FEATURE
 }
 }

@@ -65,14 +65,14 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  *                | choice       | 7.9     | 0..n        |-child nodes      |
  *                | choice       | 7.9     | 0..n        |-child nodes      |
  *                | container    | 7.5     | 0..n        |-child nodes      |
  *                | container    | 7.5     | 0..n        |-child nodes      |
  *                | description  | 7.19.3  | 0..1        |-string           |
  *                | description  | 7.19.3  | 0..1        |-string           |
- *                | if-feature   | 7.18.2  | 0..n        |-TODO             |
+ *                | if-feature   | 7.18.2  | 0..n        |-YangIfFeature    |
  *                | leaf         | 7.6     | 0..n        |-YangLeaf         |
  *                | leaf         | 7.6     | 0..n        |-YangLeaf         |
  *                | leaf-list    | 7.7     | 0..n        |-YangLeafList     |
  *                | leaf-list    | 7.7     | 0..n        |-YangLeafList     |
  *                | list         | 7.8     | 0..n        |-child nodes      |
  *                | list         | 7.8     | 0..n        |-child nodes      |
  *                | reference    | 7.19.4  | 0..1        |-String           |
  *                | reference    | 7.19.4  | 0..1        |-String           |
  *                | status       | 7.19.2  | 0..1        |-YangStatus       |
  *                | status       | 7.19.2  | 0..1        |-YangStatus       |
  *                | uses         | 7.12    | 0..n        |-child nodes      |
  *                | uses         | 7.12    | 0..n        |-child nodes      |
- *                | when         | 7.19.5  | 0..1        |-TODO             |
+ *                | when         | 7.19.5  | 0..1        |-YangWhen         |
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  */
  */
 
 
@@ -81,7 +81,7 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  */
  */
 public class YangAugment
 public class YangAugment
         extends YangNode
         extends YangNode
-        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector {
+        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangWhenHolder, YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201602L;
     private static final long serialVersionUID = 806201602L;
 
 
@@ -121,6 +121,16 @@ public class YangAugment
     private YangStatusType status;
     private YangStatusType status;
 
 
     /**
     /**
+     * When data of the node.
+     */
+    private YangWhen when;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Create a YANG augment node.
      * Create a YANG augment node.
      */
      */
     public YangAugment() {
     public YangAugment() {
@@ -146,6 +156,26 @@ public class YangAugment
     }
     }
 
 
     /**
     /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    @Override
+    public YangWhen getWhen() {
+        return when;
+    }
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    @Override
+    public void setWhen(YangWhen when) {
+        this.when = when;
+    }
+
+    /**
      * Returns the description.
      * Returns the description.
      *
      *
      * @return the description
      * @return the description
@@ -341,4 +371,21 @@ public class YangAugment
         this.name = name;
         this.name = name;
     }
     }
 
 
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
 }
 }

@@ -78,14 +78,14 @@ import static org.onosproject.yangutils.datamodel.utils.YangConstructType.CASE_D
  *                | choice       | 7.9     | 0..n        |-child nodes      |
  *                | choice       | 7.9     | 0..n        |-child nodes      |
  *                | container    | 7.5     | 0..n        |-child nodes      |
  *                | container    | 7.5     | 0..n        |-child nodes      |
  *                | description  | 7.19.3  | 0..1        |-string           |
  *                | description  | 7.19.3  | 0..1        |-string           |
- *                | if-feature   | 7.18.2  | 0..n        |-TODO             |
+ *                | if-feature   | 7.18.2  | 0..n        |-YangIfFeature    |
  *                | leaf         | 7.6     | 0..n        |-YangLeaf         |
  *                | leaf         | 7.6     | 0..n        |-YangLeaf         |
  *                | leaf-list    | 7.7     | 0..n        |-YangLeafList     |
  *                | leaf-list    | 7.7     | 0..n        |-YangLeafList     |
  *                | list         | 7.8     | 0..n        |-child nodes      |
  *                | list         | 7.8     | 0..n        |-child nodes      |
  *                | reference    | 7.19.4  | 0..1        |-string           |
  *                | reference    | 7.19.4  | 0..1        |-string           |
  *                | status       | 7.19.2  | 0..1        |-YangStatus       |
  *                | status       | 7.19.2  | 0..1        |-YangStatus       |
  *                | uses         | 7.12    | 0..n        |-child node       |
  *                | uses         | 7.12    | 0..n        |-child node       |
- *                | when         | 7.19.5  | 0..1        |-TODO             |
+ *                | when         | 7.19.5  | 0..1        |-YangWhen         |
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  */
  */
 
 
@@ -94,7 +94,8 @@ import static org.onosproject.yangutils.datamodel.utils.YangConstructType.CASE_D
  */
  */
 public class YangCase
 public class YangCase
         extends YangNode
         extends YangNode
-        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder {
+        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder,
+        YangWhenHolder, YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201603L;
     private static final long serialVersionUID = 806201603L;
 
 
@@ -131,6 +132,16 @@ public class YangCase
     private YangStatusType status;
     private YangStatusType status;
 
 
     /**
     /**
+     * When data of the node.
+     */
+    private YangWhen when;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Creates a choice node.
      * Creates a choice node.
      */
      */
     public YangCase() {
     public YangCase() {
@@ -138,6 +149,26 @@ public class YangCase
     }
     }
 
 
     /**
     /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    @Override
+    public YangWhen getWhen() {
+        return when;
+    }
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    @Override
+    public void setWhen(YangWhen when) {
+        this.when = when;
+    }
+
+    /**
      * Returns the case name.
      * Returns the case name.
      *
      *
      * @return case name
      * @return case name
@@ -343,4 +374,22 @@ public class YangCase
         // Asks helper to detect colliding child.
         // Asks helper to detect colliding child.
         detectCollidingChildUtil(identifierName, dataType, this);
         detectCollidingChildUtil(identifierName, dataType, this);
     }
     }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
 }
 }

@@ -15,6 +15,8 @@
  */
  */
 package org.onosproject.yangutils.datamodel;
 package org.onosproject.yangutils.datamodel;
 
 
+import java.util.LinkedList;
+import java.util.List;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
@@ -46,21 +48,23 @@ import static org.onosproject.yangutils.datamodel.utils.YangConstructType.CHOICE
  *                | container    | 7.5     | 0..n        |-child case nodes |
  *                | container    | 7.5     | 0..n        |-child case nodes |
  *                | default      | 7.9.3   | 0..1        |-string           |
  *                | default      | 7.9.3   | 0..1        |-string           |
  *                | description  | 7.19.3  | 0..1        |-string           |
  *                | description  | 7.19.3  | 0..1        |-string           |
- *                | if-feature   | 7.18.2  | 0..n        |-TODO             |
+ *                | if-feature   | 7.18.2  | 0..n        |-YangIfFeature    |
  *                | leaf         | 7.6     | 0..n        |-child case nodes |
  *                | leaf         | 7.6     | 0..n        |-child case nodes |
  *                | leaf-list    | 7.7     | 0..n        |-child case nodes |
  *                | leaf-list    | 7.7     | 0..n        |-child case nodes |
  *                | list         | 7.8     | 0..n        |-child case nodes |
  *                | list         | 7.8     | 0..n        |-child case nodes |
  *                | mandatory    | 7.9.4   | 0..1        |-string           |
  *                | mandatory    | 7.9.4   | 0..1        |-string           |
  *                | reference    | 7.19.4  | 0..1        |-string           |
  *                | reference    | 7.19.4  | 0..1        |-string           |
  *                | status       | 7.19.2  | 0..1        |-string           |
  *                | status       | 7.19.2  | 0..1        |-string           |
- *                | when         | 7.19.5  | 0..1        |-TODO             |
+ *                | when         | 7.19.5  | 0..1        |-YangWhen         |
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  */
  */
+
 /**
 /**
  * Represents data model node to maintain information defined in YANG choice.
  * Represents data model node to maintain information defined in YANG choice.
  */
  */
 public class YangChoice extends YangNode
 public class YangChoice extends YangNode
-        implements YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder {
+        implements YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder, YangWhenHolder,
+        YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201604L;
     private static final long serialVersionUID = 806201604L;
 
 
@@ -143,6 +147,16 @@ public class YangChoice extends YangNode
     private String defaultValueInString;
     private String defaultValueInString;
 
 
     /**
     /**
+     * When data of the node.
+     */
+    private YangWhen when;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Create a choice node.
      * Create a choice node.
      */
      */
     public YangChoice() {
     public YangChoice() {
@@ -150,6 +164,26 @@ public class YangChoice extends YangNode
     }
     }
 
 
     /**
     /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    @Override
+    public YangWhen getWhen() {
+        return when;
+    }
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    @Override
+    public void setWhen(YangWhen when) {
+        this.when = when;
+    }
+
+    /**
      * Returns the choice name.
      * Returns the choice name.
      *
      *
      * @return choice name
      * @return choice name
@@ -365,4 +399,23 @@ public class YangChoice extends YangNode
             node = node.getNextSibling();
             node = node.getNextSibling();
         }
         }
     }
     }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
+
 }
 }

@@ -70,17 +70,17 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  *                | container    | 7.5     | 0..n        | -child nodes     |
  *                | container    | 7.5     | 0..n        | -child nodes     |
  *                | description  | 7.19.3  | 0..1        | -string          |
  *                | description  | 7.19.3  | 0..1        | -string          |
  *                | grouping     | 7.11    | 0..n        | -child nodes     |
  *                | grouping     | 7.11    | 0..n        | -child nodes     |
- *                | if-feature   | 7.18.2  | 0..n        | -TODO            |
+ *                | if-feature   | 7.18.2  | 0..n        | -YangIfFeature   |
  *                | leaf         | 7.6     | 0..n        | -YangLeaf        |
  *                | leaf         | 7.6     | 0..n        | -YangLeaf        |
  *                | leaf-list    | 7.7     | 0..n        | -YangLeafList    |
  *                | leaf-list    | 7.7     | 0..n        | -YangLeafList    |
  *                | list         | 7.8     | 0..n        | -child nodes     |
  *                | list         | 7.8     | 0..n        | -child nodes     |
- *                | must         | 7.5.3   | 0..n        | -TODO            |
+ *                | must         | 7.5.3   | 0..n        | -YangMust        |
  *                | presence     | 7.5.5   | 0..1        | -boolean         |
  *                | presence     | 7.5.5   | 0..1        | -boolean         |
  *                | reference    | 7.19.4  | 0..1        | -string          |
  *                | reference    | 7.19.4  | 0..1        | -string          |
  *                | status       | 7.19.2  | 0..1        | -YangStatus      |
  *                | status       | 7.19.2  | 0..1        | -YangStatus      |
  *                | typedef      | 7.3     | 0..n        | -child nodes     |
  *                | typedef      | 7.3     | 0..n        | -child nodes     |
  *                | uses         | 7.12    | 0..n        | -child nodes     |
  *                | uses         | 7.12    | 0..n        | -child nodes     |
- *                | when         | 7.19.5  | 0..1        | -TODO            |
+ *                | when         | 7.19.5  | 0..1        | -YangWhen        |
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  */
  */
 
 
@@ -89,7 +89,8 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  */
  */
 public class YangContainer
 public class YangContainer
         extends YangNode
         extends YangNode
-        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder {
+        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder,
+        YangMustHolder, YangWhenHolder, YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201605L;
     private static final long serialVersionUID = 806201605L;
 
 
@@ -135,6 +136,21 @@ public class YangContainer
     private YangStatusType status = YangStatusType.CURRENT;
     private YangStatusType status = YangStatusType.CURRENT;
 
 
     /**
     /**
+     * List of must statement constraints.
+     */
+    private List<YangMust> mustConstraintList;
+
+    /**
+     * When data of the node.
+     */
+    private YangWhen when;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Create a container node.
      * Create a container node.
      */
      */
     public YangContainer() {
     public YangContainer() {
@@ -142,6 +158,26 @@ public class YangContainer
     }
     }
 
 
     /**
     /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    @Override
+    public YangWhen getWhen() {
+        return when;
+    }
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    @Override
+    public void setWhen(YangWhen when) {
+        this.when = when;
+    }
+
+    /**
      * Returns the YANG name of container.
      * Returns the YANG name of container.
      *
      *
      * @return the name of container as defined in YANG file
      * @return the name of container as defined in YANG file
@@ -445,4 +481,41 @@ public class YangContainer
                     + getName() + "\"");
                     + getName() + "\"");
         }
         }
     }
     }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
+
+    @Override
+    public List<YangMust> getListOfMust() {
+        return mustConstraintList;
+    }
+
+    @Override
+    public void setListOfMust(List<YangMust> mustConstraintList) {
+        this.mustConstraintList = mustConstraintList;
+    }
+
+    @Override
+    public void addMust(YangMust must) {
+        if (getListOfMust() == null) {
+            setListOfMust(new LinkedList<>());
+        }
+        getListOfMust().add(must);
+    }
+
 }
 }

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.datamodel;
+
+import java.io.Serializable;
+import java.util.LinkedList;
+import java.util.List;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
+import org.onosproject.yangutils.datamodel.utils.YangConstructType;
+
+/*
+ * Reference RFC 6020.
+ *
+ * The "feature" statement is used to define a mechanism by which
+ * portions of the schema are marked as conditional.  A feature name is
+ * defined that can later be referenced using the "if-feature" statement.
+ * Schema nodes tagged with a feature are ignored by the device unless
+ * the device supports the given feature.  This allows portions of the
+ * YANG module to be conditional based on conditions on the device.
+ * The model can represent the abilities of the device within the model,
+ * giving a richer model that allows for differing device abilities and roles.
+ *
+ * The argument to the "feature" statement is the name of the new
+ * feature, and follows the rules for identifiers.  This name is used by the
+ * "if-feature" statement to tie the schema nodes to the feature.
+ *
+ * The feature's Substatements
+ *
+ *                +--------------+---------+-------------+------------------+
+ *                | substatement | section | cardinality |data model mapping|
+ *                +--------------+---------+-------------+------------------+
+ *                | description  | 7.19.3  | 0..1        | -string          |
+ *                | if-feature   | 7.18.2  | 0..n        | -YangIfFeature   |
+ *                | reference    | 7.19.4  | 0..1        | -string          |
+ *                | status       | 7.19.2  | 0..1        | -YangStatus      |
+ *                +--------------+---------+-------------+------------------+
+ */
+
+/**
+ * Represents data model node to maintain information defined in YANG feature.
+ */
+public class YangFeature implements YangCommonInfo, Parsable, YangIfFeatureHolder, Serializable {
+
+    private static final long serialVersionUID = 806201635L;
+
+    /**
+     * Name of the feature.
+     */
+    private String name;
+
+    /**
+     * Description of feature.
+     */
+    private String description;
+
+    /**
+     * Reference of the feature.
+     */
+    private String reference;
+
+    /**
+     * Status of feature.
+     */
+    private YangStatusType statusType;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    @Override
+    public String getDescription() {
+        return description;
+    }
+
+    @Override
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    @Override
+    public String getReference() {
+        return reference;
+    }
+
+    @Override
+    public void setReference(String reference) {
+        this.reference = reference;
+    }
+
+    @Override
+    public YangStatusType getStatus() {
+        return statusType;
+    }
+
+    @Override
+    public void setStatus(YangStatusType status) {
+        this.statusType = status;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public YangConstructType getYangConstructType() {
+        return YangConstructType.FEATURE_DATA;
+    }
+
+    @Override
+    public void validateDataOnEntry() throws DataModelException {
+        //TODO : To be implemented
+    }
+
+    @Override
+    public void validateDataOnExit() throws DataModelException {
+        //TODO : To be implemented
+    }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
+}

+/*Copyright 2016.year Open Networking Laboratory
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.*/
+
+package org.onosproject.yangutils.datamodel;
+
+import java.util.List;
+
+/**
+ * Abstraction of feature entity. It is used to abstract the data holders of feature.
+ */
+public interface YangFeatureHolder {
+
+    /**
+     * Returns the list of feature from data holder like container / list.
+     *
+     * @return the list of feature
+     */
+    List<YangFeature> getFeatureList();
+
+    /**
+     * Adds feature in feature list.
+     *
+     * @param feature the feature to be added
+     */
+    void addFeatureList(YangFeature feature);
+
+    /**
+     * Sets the list of feature.
+     *
+     * @param listOfFeature the list of feature to set
+     */
+    void setListOfFeature(List<YangFeature> listOfFeature);
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.datamodel;
+
+import java.io.Serializable;
+import java.util.Iterator;
+import java.util.List;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
+import org.onosproject.yangutils.datamodel.utils.ResolvableStatus;
+import org.onosproject.yangutils.datamodel.utils.YangConstructType;
+
+/*
+ * Reference RFC 6020.
+ *
+ *  The "if-feature" statement makes its parent statement conditional.
+ *  The argument is the name of a feature, as defined by a "feature"
+ *  statement.  The parent statement is implemented by servers that
+ *  support this feature.  If a prefix is present on the feature name, it
+ *  refers to a feature defined in the module that was imported with that
+ *  prefix, or the local module if the prefix matches the local module's
+ *  prefix.  Otherwise, a feature with the matching name MUST be defined
+ *  in the current module or an included submodule.
+ *
+ *  Since submodules cannot include the parent module, any features in
+ *  the module that need to be exposed to submodules MUST be defined in a
+ *  submodule.  Submodules can then include this submodule to find the
+ *  definition of the feature.
+ */
+
+/**
+ * Represents data model node to maintain information defined in YANG if-feature.
+ */
+public class YangIfFeature implements Parsable, Resolvable, Serializable {
+
+    private static final long serialVersionUID = 806201635L;
+
+    /**
+     * if-feature argument.
+     */
+    YangNodeIdentifier name;
+
+    /**
+     * Referred feature information.
+     */
+    YangFeature referredFeature;
+
+    /**
+     * Referred feature parent information.
+     */
+    YangNode referredFeatureHolder;
+
+    /**
+     * Status of resolution. If completely resolved enum value is "RESOLVED",
+     * if not enum value is "UNRESOLVED", in case reference of grouping/typedef
+     * is added to uses/type but it's not resolved value of enum should be
+     * "INTRA_FILE_RESOLVED".
+     */
+    private ResolvableStatus resolvableStatus;
+
+    /**
+     * Returns referred feature holder.
+     *
+     * @return referred feature holder
+     */
+    public YangNode getReferredFeatureHolder() {
+        return referredFeatureHolder;
+    }
+
+    /**
+     * Sets the referred feature holder.
+     *
+     * @param referredFeatureHolder referred feature holder
+     */
+    public void setReferredFeatureHolder(YangNode referredFeatureHolder) {
+        this.referredFeatureHolder = referredFeatureHolder;
+    }
+
+    /**
+     * Returns prefix associated with identifier.
+     *
+     * @return prefix associated with identifier
+     */
+    public String getPrefix() {
+        return name.getPrefix();
+    }
+
+    /**
+     * Sets prefix associated with identifier.
+     *
+     * @param prefix prefix associated with identifier
+     */
+    public void setPrefix(String prefix) {
+        name.setPrefix(prefix);
+    }
+
+    /**
+     * Returns referred feature associated with if-feature.
+     *
+     * @return referred feature associated with if-feature
+     */
+    public YangFeature getReferredFeature() {
+        return referredFeature;
+    }
+
+    /**
+     * Sets referred feature associated with if-feature.
+     *
+     * @param referredFeature referred feature associated with if-feature
+     */
+    public void setReferredFeature(YangFeature referredFeature) {
+        this.referredFeature = referredFeature;
+    }
+
+    /**
+     * Returns the YANG name of if-feature.
+     *
+     * @return the name of if-feature as defined in YANG file
+     */
+    public YangNodeIdentifier getName() {
+        return name;
+    }
+
+    /**
+     * Sets the YANG name of if-feature.
+     *
+     * @param name the name of if-feature as defined in YANG file
+     */
+    public void setName(YangNodeIdentifier name) {
+        this.name = name;
+    }
+
+    @Override
+    public YangConstructType getYangConstructType() {
+        return YangConstructType.IF_FEATURE_DATA;
+    }
+
+    @Override
+    public void validateDataOnEntry() throws DataModelException {
+        // do nothing, no validation required for if-feature
+    }
+
+    @Override
+    public void validateDataOnExit() throws DataModelException {
+        // do nothing, no validation required for if-feature
+    }
+
+    @Override
+    public ResolvableStatus getResolvableStatus() {
+        return resolvableStatus;
+    }
+
+    @Override
+    public void setResolvableStatus(ResolvableStatus resolvableStatus) {
+        this.resolvableStatus = resolvableStatus;
+    }
+
+    @Override
+    public void resolve() throws DataModelException {
+        YangFeature feature = getReferredFeature();
+
+        // check whether feature has if-feature
+        List<YangIfFeature> ifFeatureList = feature.getIfFeatureList();
+        if (ifFeatureList != null && !ifFeatureList.isEmpty()) {
+            Iterator<YangIfFeature> ifFeatureIterator = ifFeatureList.iterator();
+            while (ifFeatureIterator.hasNext()) {
+                YangIfFeature ifFeature = ifFeatureIterator.next();
+                if (ifFeature.getResolvableStatus() != ResolvableStatus.RESOLVED) {
+                    setResolvableStatus(ResolvableStatus.INTRA_FILE_RESOLVED);
+                    return;
+                }
+            }
+        }
+    }
+}

+/*Copyright 2016.year Open Networking Laboratory
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.*/
+
+package org.onosproject.yangutils.datamodel;
+
+import java.util.List;
+
+/**
+ * Abstraction of if-feature entity. It is used to abstract the data holders of if-feature.
+ */
+public interface YangIfFeatureHolder {
+
+    /**
+     * Returns the list of if-feature from data holder like container / list.
+     *
+     * @return the list of if-feature
+     */
+    List<YangIfFeature> getIfFeatureList();
+
+    /**
+     * Adds if-feature in if-feature list.
+     *
+     * @param ifFeature the if-feature to be added
+     */
+    void addIfFeatureList(YangIfFeature ifFeature);
+
+    /**
+     * Sets the list of if-feature.
+     *
+     * @param ifFeatureList the list of if-feature to set
+     */
+    void setIfFeatureList(List<YangIfFeature> ifFeatureList);
+}

@@ -16,6 +16,7 @@
 package org.onosproject.yangutils.datamodel;
 package org.onosproject.yangutils.datamodel;
 
 
 import java.io.Serializable;
 import java.io.Serializable;
+import java.util.Date;
 import java.util.Set;
 import java.util.Set;
 
 
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
@@ -61,7 +62,7 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.findRefer
  *                | substatement  | section | cardinality |data model mapping|
  *                | substatement  | section | cardinality |data model mapping|
  *                +---------------+---------+-------------+------------------+
  *                +---------------+---------+-------------+------------------+
  *                | prefix        | 7.1.4   | 1           | string           |
  *                | prefix        | 7.1.4   | 1           | string           |
- *                | revision-date | 7.1.5.1 | 0..1        | string           |
+ *                | revision-date | 7.1.5.1 | 0..1        | Date             |
  *                +---------------+---------+-------------+------------------+
  *                +---------------+---------+-------------+------------------+
  */
  */
 
 
@@ -91,7 +92,7 @@ public class YangImport
      * the most recent "revision" statement in the imported module. organization
      * the most recent "revision" statement in the imported module. organization
      * which defined the YANG module.
      * which defined the YANG module.
      */
      */
-    private String revision;
+    private Date revision;
 
 
     /**
     /**
      * Reference to node which is imported.
      * Reference to node which is imported.
@@ -152,7 +153,7 @@ public class YangImport
      *
      *
      * @return the revision of the imported module
      * @return the revision of the imported module
      */
      */
-    public String getRevision() {
+    public Date getRevision() {
         return revision;
         return revision;
     }
     }
 
 
@@ -161,7 +162,7 @@ public class YangImport
      *
      *
      * @param rev set the revision of the imported module
      * @param rev set the revision of the imported module
      */
      */
-    public void setRevision(String rev) {
+    public void setRevision(Date rev) {
         revision = rev;
         revision = rev;
     }
     }
 
 
@@ -245,7 +246,7 @@ public class YangImport
      */
      */
     public void addReferenceToImport(Set<YangNode> yangNodeSet) throws DataModelException {
     public void addReferenceToImport(Set<YangNode> yangNodeSet) throws DataModelException {
         String importedModuleName = getModuleName();
         String importedModuleName = getModuleName();
-        String importedModuleRevision = getRevision();
+        Date importedModuleRevision = getRevision();
         YangNode moduleNode = null;
         YangNode moduleNode = null;
         /*
         /*
          * Find the imported module node for a given module name with a
          * Find the imported module node for a given module name with a
@@ -266,7 +267,7 @@ public class YangImport
 
 
         if (moduleNode != null) {
         if (moduleNode != null) {
             if (moduleNode instanceof YangModule) {
             if (moduleNode instanceof YangModule) {
-                if (getRevision() == null || getRevision().isEmpty()) {
+                if (getRevision() == null) {
                     setImportedNode(moduleNode);
                     setImportedNode(moduleNode);
                     return;
                     return;
                 }
                 }

@@ -16,6 +16,7 @@
 package org.onosproject.yangutils.datamodel;
 package org.onosproject.yangutils.datamodel;
 
 
 import java.io.Serializable;
 import java.io.Serializable;
+import java.util.Date;
 import java.util.Set;
 import java.util.Set;
 
 
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
@@ -56,7 +57,7 @@ public class YangInclude
      * The include's "revision-date" statement is used to specify the exact
      * The include's "revision-date" statement is used to specify the exact
      * version of the submodule to import.
      * version of the submodule to import.
      */
      */
-    private String revision;
+    private Date revision;
 
 
     /**
     /**
      * Reference to node which is included.
      * Reference to node which is included.
@@ -98,7 +99,7 @@ public class YangInclude
      *
      *
      * @return the revision
      * @return the revision
      */
      */
-    public String getRevision() {
+    public Date getRevision() {
         return revision;
         return revision;
     }
     }
 
 
@@ -107,7 +108,7 @@ public class YangInclude
      *
      *
      * @param revision the revision to set
      * @param revision the revision to set
      */
      */
-    public void setRevision(String revision) {
+    public void setRevision(Date revision) {
         this.revision = revision;
         this.revision = revision;
     }
     }
 
 
@@ -182,7 +183,7 @@ public class YangInclude
      */
      */
     public YangSubModule addReferenceToInclude(Set<YangNode> yangNodeSet) throws DataModelException {
     public YangSubModule addReferenceToInclude(Set<YangNode> yangNodeSet) throws DataModelException {
         String includedSubModuleName = getSubModuleName();
         String includedSubModuleName = getSubModuleName();
-        String includedSubModuleRevision = getRevision();
+        Date includedSubModuleRevision = getRevision();
         YangNode subModuleNode = null;
         YangNode subModuleNode = null;
 
 
         /*
         /*
@@ -204,7 +205,7 @@ public class YangInclude
 
 
         if (subModuleNode != null) {
         if (subModuleNode != null) {
             if (subModuleNode instanceof YangSubModule) {
             if (subModuleNode instanceof YangSubModule) {
-                if (getRevision() == null || getRevision().isEmpty()) {
+                if (getRevision() == null) {
                     setIncludedNode(subModuleNode);
                     setIncludedNode(subModuleNode);
                     return (YangSubModule) subModuleNode;
                     return (YangSubModule) subModuleNode;
                 }
                 }

@@ -17,7 +17,8 @@
 package org.onosproject.yangutils.datamodel;
 package org.onosproject.yangutils.datamodel;
 
 
 import java.io.Serializable;
 import java.io.Serializable;
-
+import java.util.LinkedList;
+import java.util.List;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
@@ -43,16 +44,16 @@ import org.onosproject.yangutils.datamodel.utils.YangConstructType;
  *       | substatement | section | cardinality |data model mapping|
  *       | substatement | section | cardinality |data model mapping|
  *       +--------------+---------+-------------+------------------+
  *       +--------------+---------+-------------+------------------+
  *       | config       | 7.19.1  | 0..1        | - boolean        |
  *       | config       | 7.19.1  | 0..1        | - boolean        |
- *       | default      | 7.6.4   | 0..1        | - TODO           |
+ *       | default      | 7.6.4   | 0..1        | - string         |
  *       | description  | 7.19.3  | 0..1        | - string         |
  *       | description  | 7.19.3  | 0..1        | - string         |
- *       | if-feature   | 7.18.2  | 0..n        | - TODO           |
+ *       | if-feature   | 7.18.2  | 0..n        | - YangIfFeature  |
  *       | mandatory    | 7.6.5   | 0..1        | - boolean        |
  *       | mandatory    | 7.6.5   | 0..1        | - boolean        |
- *       | must         | 7.5.3   | 0..n        | - TODO           |
+ *       | must         | 7.5.3   | 0..n        | - YangMust       |
  *       | reference    | 7.19.4  | 0..1        | - string         |
  *       | reference    | 7.19.4  | 0..1        | - string         |
  *       | status       | 7.19.2  | 0..1        | - YangStatus     |
  *       | status       | 7.19.2  | 0..1        | - YangStatus     |
  *       | type         | 7.6.3   | 1           | - YangType       |
  *       | type         | 7.6.3   | 1           | - YangType       |
  *       | units        | 7.3.3   | 0..1        | - String         |
  *       | units        | 7.3.3   | 0..1        | - String         |
- *       | when         | 7.19.5  | 0..1        | - TODO           |
+ *       | when         | 7.19.5  | 0..1        | - YangWhen       |
  *       +--------------+---------+-------------+------------------+
  *       +--------------+---------+-------------+------------------+
  */
  */
 
 
@@ -60,7 +61,8 @@ import org.onosproject.yangutils.datamodel.utils.YangConstructType;
  * Represents leaf data represented in YANG.
  * Represents leaf data represented in YANG.
  */
  */
 public class YangLeaf
 public class YangLeaf
-        implements YangCommonInfo, Parsable, Cloneable, Serializable {
+        implements YangCommonInfo, Parsable, Cloneable, Serializable,
+        YangMustHolder, YangIfFeatureHolder, YangWhenHolder {
 
 
     private static final long serialVersionUID = 806201635L;
     private static final long serialVersionUID = 806201635L;
 
 
@@ -111,11 +113,26 @@ public class YangLeaf
     private String defaultValueInString;
     private String defaultValueInString;
 
 
     /**
     /**
+     * When data of the leaf.
+     */
+    private YangWhen when;
+
+    /**
      * YANG Node in which the leaf is contained.
      * YANG Node in which the leaf is contained.
      */
      */
     private transient YangLeavesHolder containedIn;
     private transient YangLeavesHolder containedIn;
 
 
     /**
     /**
+     * List of must statement constraints.
+     */
+    private List<YangMust> mustConstraintList;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Creates a YANG leaf.
      * Creates a YANG leaf.
      */
      */
     public YangLeaf() {
     public YangLeaf() {
@@ -158,6 +175,26 @@ public class YangLeaf
     }
     }
 
 
     /**
     /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    @Override
+    public YangWhen getWhen() {
+        return when;
+    }
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    @Override
+    public void setWhen(YangWhen when) {
+        this.when = when;
+    }
+
+    /**
      * Returns the description.
      * Returns the description.
      *
      *
      * @return the description
      * @return the description
@@ -346,4 +383,40 @@ public class YangLeaf
         // TODO auto-generated method stub, to be implemented by parser
         // TODO auto-generated method stub, to be implemented by parser
 
 
     }
     }
+
+    @Override
+    public List<YangMust> getListOfMust() {
+        return mustConstraintList;
+    }
+
+    @Override
+    public void setListOfMust(List<YangMust> mustConstraintList) {
+        this.mustConstraintList = mustConstraintList;
+    }
+
+    @Override
+    public void addMust(YangMust must) {
+        if (getListOfMust() == null) {
+            setListOfMust(new LinkedList<>());
+        }
+        getListOfMust().add(must);
+    }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
 }
 }

@@ -17,7 +17,8 @@
 package org.onosproject.yangutils.datamodel;
 package org.onosproject.yangutils.datamodel;
 
 
 import java.io.Serializable;
 import java.io.Serializable;
-
+import java.util.LinkedList;
+import java.util.List;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
@@ -39,16 +40,16 @@ import org.onosproject.yangutils.datamodel.utils.YangConstructType;
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  *                | config       | 7.19.1  | 0..1        | -boolean         |
  *                | config       | 7.19.1  | 0..1        | -boolean         |
  *                | description  | 7.19.3  | 0..1        | -string          |
  *                | description  | 7.19.3  | 0..1        | -string          |
- *                | if-feature   | 7.18.2  | 0..n        | -TODO            |
+ *                | if-feature   | 7.18.2  | 0..n        | -YangIfFeature   |
  *                | max-elements | 7.7.4   | 0..1        | -int             |
  *                | max-elements | 7.7.4   | 0..1        | -int             |
  *                | min-elements | 7.7.3   | 0..1        | -int             |
  *                | min-elements | 7.7.3   | 0..1        | -int             |
- *                | must         | 7.5.3   | 0..n        | -TODO            |
+ *                | must         | 7.5.3   | 0..n        | -YangMust        |
  *                | ordered-by   | 7.7.5   | 0..1        | -TODO            |
  *                | ordered-by   | 7.7.5   | 0..1        | -TODO            |
  *                | reference    | 7.19.4  | 0..1        | -string          |
  *                | reference    | 7.19.4  | 0..1        | -string          |
  *                | status       | 7.19.2  | 0..1        | -YangStatus      |
  *                | status       | 7.19.2  | 0..1        | -YangStatus      |
  *                | type         | 7.4     | 1           | -YangType        |
  *                | type         | 7.4     | 1           | -YangType        |
  *                | units        | 7.3.3   | 0..1        | -string          |
  *                | units        | 7.3.3   | 0..1        | -string          |
- *                | when         | 7.19.5  | 0..1        | -TODO            |
+ *                | when         | 7.19.5  | 0..1        | -YangWhen        |
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  */
  */
 
 
@@ -56,7 +57,8 @@ import org.onosproject.yangutils.datamodel.utils.YangConstructType;
  * Represents leaf-list data represented in YANG.
  * Represents leaf-list data represented in YANG.
  */
  */
 public class YangLeafList
 public class YangLeafList
-        implements YangCommonInfo, Parsable, Cloneable, Serializable {
+        implements YangCommonInfo, Parsable, Cloneable, Serializable,
+        YangMustHolder, YangWhenHolder, YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201637L;
     private static final long serialVersionUID = 806201637L;
 
 
@@ -133,6 +135,21 @@ public class YangLeafList
     private transient YangLeavesHolder containedIn;
     private transient YangLeavesHolder containedIn;
 
 
     /**
     /**
+     * List of must statement constraints.
+     */
+    private List<YangMust> mustConstraintList;
+
+    /**
+     * When data of the leaf.
+     */
+    private YangWhen when;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Creates a YANG leaf-list.
      * Creates a YANG leaf-list.
      */
      */
     public YangLeafList() {
     public YangLeafList() {
@@ -175,6 +192,26 @@ public class YangLeafList
     }
     }
 
 
     /**
     /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    @Override
+    public YangWhen getWhen() {
+        return when;
+    }
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    @Override
+    public void setWhen(YangWhen when) {
+        this.when = when;
+    }
+
+    /**
      * Returns the description.
      * Returns the description.
      *
      *
      * @return the description
      * @return the description
@@ -363,4 +400,40 @@ public class YangLeafList
         // TODO auto-generated method stub, to be implemented by parser
         // TODO auto-generated method stub, to be implemented by parser
 
 
     }
     }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
+
+    @Override
+    public List<YangMust> getListOfMust() {
+        return mustConstraintList;
+    }
+
+    @Override
+    public void setListOfMust(List<YangMust> mustConstraintList) {
+        this.mustConstraintList = mustConstraintList;
+    }
+
+    @Override
+    public void addMust(YangMust must) {
+        if (getListOfMust() == null) {
+            setListOfMust(new LinkedList<>());
+        }
+        getListOfMust().add(must);
+    }
 }
 }

@@ -46,21 +46,21 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  *                | container    | 7.5     | 0..n        |-child nodes      |
  *                | container    | 7.5     | 0..n        |-child nodes      |
  *                | description  | 7.19.3  | 0..1        |-string           |
  *                | description  | 7.19.3  | 0..1        |-string           |
  *                | grouping     | 7.11    | 0..n        |-child nodes      |
  *                | grouping     | 7.11    | 0..n        |-child nodes      |
- *                | if-feature   | 7.18.2  | 0..n        |-TODO             |
+ *                | if-feature   | 7.18.2  | 0..n        |-YangIfFeature    |
  *                | key          | 7.8.2   | 0..1        |-String list      |
  *                | key          | 7.8.2   | 0..1        |-String list      |
  *                | leaf         | 7.6     | 0..n        |-YangLeaf         |
  *                | leaf         | 7.6     | 0..n        |-YangLeaf         |
  *                | leaf-list    | 7.7     | 0..n        |-YangLeafList     |
  *                | leaf-list    | 7.7     | 0..n        |-YangLeafList     |
  *                | list         | 7.8     | 0..n        |-child nodes      |
  *                | list         | 7.8     | 0..n        |-child nodes      |
  *                | max-elements | 7.7.4   | 0..1        |-int              |
  *                | max-elements | 7.7.4   | 0..1        |-int              |
  *                | min-elements | 7.7.3   | 0..1        |-int              |
  *                | min-elements | 7.7.3   | 0..1        |-int              |
- *                | must         | 7.5.3   | 0..n        |-TODO             |
+ *                | must         | 7.5.3   | 0..n        |-YangMust         |
  *                | ordered-by   | 7.7.5   | 0..1        |-TODO             |
  *                | ordered-by   | 7.7.5   | 0..1        |-TODO             |
  *                | reference    | 7.19.4  | 0..1        |-string           |
  *                | reference    | 7.19.4  | 0..1        |-string           |
  *                | status       | 7.19.2  | 0..1        |-YangStatus       |
  *                | status       | 7.19.2  | 0..1        |-YangStatus       |
  *                | typedef      | 7.3     | 0..n        |-child nodes      |
  *                | typedef      | 7.3     | 0..n        |-child nodes      |
  *                | unique       | 7.8.3   | 0..n        |-TODO             |
  *                | unique       | 7.8.3   | 0..n        |-TODO             |
- *                | uses         | 7.12    | 0..n        |-child nodes(TODO)|
- *                | when         | 7.19.5  | 0..1        |-TODO             |
+ *                | uses         | 7.12    | 0..n        |-child nodes      |
+ *                | when         | 7.19.5  | 0..1        |-YangWhen         |
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  */
  */
 
 
@@ -69,7 +69,8 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  */
  */
 public class YangList
 public class YangList
         extends YangNode
         extends YangNode
-        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder {
+        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder,
+        YangMustHolder, YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201609L;
     private static final long serialVersionUID = 806201609L;
 
 
@@ -165,10 +166,24 @@ public class YangList
     /**
     /**
      * Status of the node.
      * Status of the node.
      */
      */
-
     private YangStatusType status = YangStatusType.CURRENT;
     private YangStatusType status = YangStatusType.CURRENT;
 
 
     /**
     /**
+     * List of must statement constraints.
+     */
+    private List<YangMust> mustConstraintList;
+
+    /**
+     * When data of the node.
+     */
+    private YangWhen when;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Creates a YANG list object.
      * Creates a YANG list object.
      */
      */
     public YangList() {
     public YangList() {
@@ -176,6 +191,24 @@ public class YangList
     }
     }
 
 
     /**
     /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    public YangWhen getWhen() {
+        return when;
+    }
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    public void setWhen(YangWhen when) {
+        this.when = when;
+    }
+
+    /**
      * Returns the YANG list name.
      * Returns the YANG list name.
      *
      *
      * @return YANG list name
      * @return YANG list name
@@ -643,4 +676,40 @@ public class YangList
         return false;
         return false;
         // TODO When grouping linking is done this method has to be modified.
         // TODO When grouping linking is done this method has to be modified.
     }
     }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
+
+    @Override
+    public List<YangMust> getListOfMust() {
+        return mustConstraintList;
+    }
+
+    @Override
+    public void setListOfMust(List<YangMust> mustConstraintList) {
+        this.mustConstraintList = mustConstraintList;
+    }
+
+    @Override
+    public void addMust(YangMust must) {
+        if (getListOfMust() == null) {
+            setListOfMust(new LinkedList<>());
+        }
+        getListOfMust().add(must);
+    }
 }
 }

@@ -74,7 +74,7 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.resolveLi
 public class YangModule
 public class YangModule
         extends YangNode
         extends YangNode
         implements YangLeavesHolder, YangDesc, YangReference, Parsable, CollisionDetector, YangReferenceResolver,
         implements YangLeavesHolder, YangDesc, YangReference, Parsable, CollisionDetector, YangReferenceResolver,
-        RpcNotificationContainer {
+        RpcNotificationContainer, YangFeatureHolder {
 
 
     private static final long serialVersionUID = 806201610L;
     private static final long serialVersionUID = 806201610L;
 
 
@@ -85,7 +85,7 @@ public class YangModule
 
 
     /**
     /**
      * Reference:RFC 6020.
      * Reference:RFC 6020.
-     * <p>
+     *
      * The "contact" statement provides contact information for the module. The
      * The "contact" statement provides contact information for the module. The
      * argument is a string that is used to specify contact information for the
      * argument is a string that is used to specify contact information for the
      * person or persons to whom technical queries concerning this module should
      * person or persons to whom technical queries concerning this module should
@@ -96,7 +96,7 @@ public class YangModule
 
 
     /**
     /**
      * Reference:RFC 6020.
      * Reference:RFC 6020.
-     * <p>
+     *
      * The "description" statement takes as an argument a string that contains a
      * The "description" statement takes as an argument a string that contains a
      * human-readable textual description of this definition. The text is
      * human-readable textual description of this definition. The text is
      * provided in a language (or languages) chosen by the module developer; for
      * provided in a language (or languages) chosen by the module developer; for
@@ -125,13 +125,18 @@ public class YangModule
     private List<YangLeafList> listOfLeafList;
     private List<YangLeafList> listOfLeafList;
 
 
     /**
     /**
+     * List of feature at root level in the module.
+     */
+    private List<YangFeature> listOfFeature;
+
+    /**
      * Name space of the module.
      * Name space of the module.
      */
      */
     private YangNameSpace nameSpace;
     private YangNameSpace nameSpace;
 
 
     /**
     /**
      * Reference:RFC 6020.
      * Reference:RFC 6020.
-     * <p>
+     *
      * The "organization" statement defines the party responsible for this
      * The "organization" statement defines the party responsible for this
      * module. The argument is a string that is used to specify a textual
      * module. The argument is a string that is used to specify a textual
      * description of the organization(s) under whose auspices this module was
      * description of the organization(s) under whose auspices this module was
@@ -201,6 +206,11 @@ public class YangModule
     private List<YangResolutionInfo> usesResolutionList;
     private List<YangResolutionInfo> usesResolutionList;
 
 
     /**
     /**
+     * if-feature resolution list.
+     */
+    private List<YangResolutionInfo> ifFeatureResolutionList;
+
+    /**
      * Creates a YANG node of module type.
      * Creates a YANG node of module type.
      */
      */
     public YangModule() {
     public YangModule() {
@@ -208,6 +218,7 @@ public class YangModule
         super(YangNodeType.MODULE_NODE);
         super(YangNodeType.MODULE_NODE);
         derivedTypeResolutionList = new LinkedList<>();
         derivedTypeResolutionList = new LinkedList<>();
         usesResolutionList = new LinkedList<>();
         usesResolutionList = new LinkedList<>();
+        ifFeatureResolutionList = new LinkedList<>();
         importList = new LinkedList<YangImport>();
         importList = new LinkedList<YangImport>();
         includeList = new LinkedList<YangInclude>();
         includeList = new LinkedList<YangInclude>();
         listOfLeaf = new LinkedList<YangLeaf>();
         listOfLeaf = new LinkedList<YangLeaf>();
@@ -373,6 +384,24 @@ public class YangModule
         getListOfLeafList().add(leafList);
         getListOfLeafList().add(leafList);
     }
     }
 
 
+    @Override
+    public List<YangFeature> getFeatureList() {
+        return listOfFeature;
+    }
+
+    @Override
+    public void addFeatureList(YangFeature feature) {
+        if (getFeatureList() == null) {
+            setListOfFeature(new LinkedList<>());
+        }
+        getFeatureList().add(feature);
+    }
+
+    @Override
+    public void setListOfFeature(List<YangFeature> listOfFeature) {
+        this.listOfFeature = listOfFeature;
+    }
+
     /**
     /**
      * Returns the name space of module elements.
      * Returns the name space of module elements.
      *
      *
@@ -558,10 +587,11 @@ public class YangModule
     public List<YangResolutionInfo> getUnresolvedResolutionList(ResolvableType type) {
     public List<YangResolutionInfo> getUnresolvedResolutionList(ResolvableType type) {
         if (type == ResolvableType.YANG_DERIVED_DATA_TYPE) {
         if (type == ResolvableType.YANG_DERIVED_DATA_TYPE) {
             return derivedTypeResolutionList;
             return derivedTypeResolutionList;
-        } else {
+        } else if (type == ResolvableType.YANG_USES) {
             return usesResolutionList;
             return usesResolutionList;
+        } else {
+            return ifFeatureResolutionList;
         }
         }
-
     }
     }
 
 
     @Override
     @Override
@@ -571,6 +601,8 @@ public class YangModule
             derivedTypeResolutionList.add(resolutionInfo);
             derivedTypeResolutionList.add(resolutionInfo);
         } else if (type == ResolvableType.YANG_USES) {
         } else if (type == ResolvableType.YANG_USES) {
             usesResolutionList.add(resolutionInfo);
             usesResolutionList.add(resolutionInfo);
+        } else if (type == ResolvableType.YANG_IF_FEATURE) {
+            ifFeatureResolutionList.add(resolutionInfo);
         }
         }
     }
     }
 
 
@@ -581,6 +613,8 @@ public class YangModule
             derivedTypeResolutionList = resolutionList;
             derivedTypeResolutionList = resolutionList;
         } else if (type == ResolvableType.YANG_USES) {
         } else if (type == ResolvableType.YANG_USES) {
             usesResolutionList = resolutionList;
             usesResolutionList = resolutionList;
+        } else if (type == ResolvableType.YANG_IF_FEATURE) {
+            ifFeatureResolutionList.add((YangResolutionInfo) resolutionList);
         }
         }
 
 
     }
     }

@@ -55,7 +55,7 @@ public class YangMust implements YangDesc, YangReference, Parsable, Serializable
     /**
     /**
      * Constraint info.
      * Constraint info.
      */
      */
-    private String constratint;
+    private String constraint;
 
 
     /**
     /**
      * Description string.
      * Description string.
@@ -78,17 +78,17 @@ public class YangMust implements YangDesc, YangReference, Parsable, Serializable
      *
      *
      * @return the constraint
      * @return the constraint
      */
      */
-    public String getConstratint() {
-        return constratint;
+    public String getConstraint() {
+        return constraint;
     }
     }
 
 
     /**
     /**
      * Sets the constraint.
      * Sets the constraint.
      *
      *
-     * @param constratint the constraint to set
+     * @param constraint the constraint to set
      */
      */
-    public void setConstratint(String constratint) {
-        this.constratint = constratint;
+    public void setConstraint(String constraint) {
+        this.constraint = constraint;
     }
     }
 
 
     /**
     /**

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.datamodel;
+
+import java.util.List;
+
+/**
+ * Abstraction of must entity. It is used to abstract the data holders of must.
+ */
+public interface YangMustHolder {
+
+    /**
+     * Returns the list of must from data holder like container / list.
+     *
+     * @return the list of must
+     */
+    List<YangMust> getListOfMust();
+
+    /**
+     * Sets the list of must.
+     *
+     * @param mustConstraintList the list of must to set
+     */
+    void setListOfMust(List<YangMust> mustConstraintList);
+
+    /**
+     * Adds must in data holder like container / list.
+     *
+     * @param must the must to be added
+     */
+    void addMust(YangMust must);
+}

@@ -60,7 +60,7 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  *      | container    | 7.5     | 0..n        | -child nodes     |
  *      | container    | 7.5     | 0..n        | -child nodes     |
  *      | description  | 7.19.3  | 0..1        | -string          |
  *      | description  | 7.19.3  | 0..1        | -string          |
  *      | grouping     | 7.11    | 0..n        | -child nodes     |
  *      | grouping     | 7.11    | 0..n        | -child nodes     |
- *      | if-feature   | 7.18.2  | 0..n        | -TODO            |
+ *      | if-feature   | 7.18.2  | 0..n        | -YangIfFeature   |
  *      | leaf         | 7.6     | 0..n        | -YangLeaf        |
  *      | leaf         | 7.6     | 0..n        | -YangLeaf        |
  *      | leaf-list    | 7.7     | 0..n        | -YangLeafList    |
  *      | leaf-list    | 7.7     | 0..n        | -YangLeafList    |
  *      | list         | 7.8     | 0..n        | -child nodes     |
  *      | list         | 7.8     | 0..n        | -child nodes     |
@@ -76,7 +76,8 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  */
  */
 public class YangNotification
 public class YangNotification
         extends YangNode
         extends YangNode
-        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder {
+        implements YangLeavesHolder, YangCommonInfo, Parsable, CollisionDetector, YangAugmentationHolder,
+        YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201611L;
     private static final long serialVersionUID = 806201611L;
 
 
@@ -111,6 +112,11 @@ public class YangNotification
     private YangStatusType status = YangStatusType.CURRENT;
     private YangStatusType status = YangStatusType.CURRENT;
 
 
     /**
     /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Create a notification node.
      * Create a notification node.
      */
      */
     public YangNotification() {
     public YangNotification() {
@@ -221,4 +227,22 @@ public class YangNotification
     public void setStatus(YangStatusType status) {
     public void setStatus(YangStatusType status) {
         this.status = status;
         this.status = status;
     }
     }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
 }
 }

@@ -16,7 +16,7 @@
 package org.onosproject.yangutils.datamodel;
 package org.onosproject.yangutils.datamodel;
 
 
 import java.io.Serializable;
 import java.io.Serializable;
-
+import java.util.Date;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
@@ -41,6 +41,7 @@ import org.onosproject.yangutils.datamodel.utils.YangConstructType;
  *                | reference    | 7.19.4  | 0..1        |sring            |
  *                | reference    | 7.19.4  | 0..1        |sring            |
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  */
  */
+
 /**
 /**
  * Represents the information about the revision.
  * Represents the information about the revision.
  */
  */
@@ -51,7 +52,7 @@ public class YangRevision implements YangDesc, YangReference, Parsable, Serializ
     /**
     /**
      * Revision date. Date string in the format "YYYY-MM-DD"
      * Revision date. Date string in the format "YYYY-MM-DD"
      */
      */
-    private String revDate;
+    private Date revDate;
 
 
     /**
     /**
      * Description of revision.
      * Description of revision.
@@ -74,7 +75,7 @@ public class YangRevision implements YangDesc, YangReference, Parsable, Serializ
      *
      *
      * @return the revision date
      * @return the revision date
      */
      */
-    public String getRevDate() {
+    public Date getRevDate() {
         return revDate;
         return revDate;
     }
     }
 
 
@@ -83,7 +84,7 @@ public class YangRevision implements YangDesc, YangReference, Parsable, Serializ
      *
      *
      * @param revDate the revision date to set
      * @param revDate the revision date to set
      */
      */
-    public void setRevDate(String revDate) {
+    public void setRevDate(Date revDate) {
         this.revDate = revDate;
         this.revDate = revDate;
     }
     }
 
 

@@ -16,6 +16,8 @@
 
 
 package org.onosproject.yangutils.datamodel;
 package org.onosproject.yangutils.datamodel;
 
 
+import java.util.LinkedList;
+import java.util.List;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
 import org.onosproject.yangutils.datamodel.utils.YangConstructType;
@@ -44,7 +46,7 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  *    +--------------+---------+-------------+------------------+
  *    +--------------+---------+-------------+------------------+
  *    | description  | 7.19.3  | 0..1        | -string          |
  *    | description  | 7.19.3  | 0..1        | -string          |
  *    | grouping     | 7.11    | 0..n        | -child nodes     |
  *    | grouping     | 7.11    | 0..n        | -child nodes     |
- *    | if-feature   | 7.18.2  | 0..n        | -TODO            |
+ *    | if-feature   | 7.18.2  | 0..n        | -YangIfFeature   |
  *    | input        | 7.13.2  | 0..1        | -child nodes     |
  *    | input        | 7.13.2  | 0..1        | -child nodes     |
  *    | output       | 7.13.3  | 0..1        | -child nodes     |
  *    | output       | 7.13.3  | 0..1        | -child nodes     |
  *    | reference    | 7.19.4  | 0..1        | -string          |
  *    | reference    | 7.19.4  | 0..1        | -string          |
@@ -57,7 +59,7 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.detectCol
  * Represents data model node to maintain information defined in YANG rpc.
  * Represents data model node to maintain information defined in YANG rpc.
  */
  */
 public class YangRpc extends YangNode implements YangCommonInfo, Parsable,
 public class YangRpc extends YangNode implements YangCommonInfo, Parsable,
-        CollisionDetector {
+        CollisionDetector, YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201613L;
     private static final long serialVersionUID = 806201613L;
 
 
@@ -82,6 +84,11 @@ public class YangRpc extends YangNode implements YangCommonInfo, Parsable,
     private YangStatusType status = YangStatusType.CURRENT;
     private YangStatusType status = YangStatusType.CURRENT;
 
 
     /**
     /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Create a rpc node.
      * Create a rpc node.
      */
      */
     public YangRpc() {
     public YangRpc() {
@@ -156,4 +163,22 @@ public class YangRpc extends YangNode implements YangCommonInfo, Parsable,
     public void setStatus(YangStatusType status) {
     public void setStatus(YangStatusType status) {
         this.status = status;
         this.status = status;
     }
     }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
 }
 }

@@ -57,7 +57,7 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.resolveLi
  *                | description  | 7.19.3  | 0..1        | - string         |
  *                | description  | 7.19.3  | 0..1        | - string         |
  *                | deviation    | 7.18.3  | 0..n        | - TODO           |
  *                | deviation    | 7.18.3  | 0..n        | - TODO           |
  *                | extension    | 7.17    | 0..n        | - TODO           |
  *                | extension    | 7.17    | 0..n        | - TODO           |
- *                | feature      | 7.18.1  | 0..n        | - TODO           |
+ *                | feature      | 7.18.1  | 0..n        | - YangFeature    |
  *                | grouping     | 7.11    | 0..n        | - child nodes    |
  *                | grouping     | 7.11    | 0..n        | - child nodes    |
  *                | identity     | 7.16    | 0..n        | - TODO           |
  *                | identity     | 7.16    | 0..n        | - TODO           |
  *                | import       | 7.1.5   | 0..n        | - YangImport     |
  *                | import       | 7.1.5   | 0..n        | - YangImport     |
@@ -82,7 +82,7 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.resolveLi
 public class YangSubModule
 public class YangSubModule
         extends YangNode
         extends YangNode
         implements YangLeavesHolder, YangDesc, YangReference, Parsable, CollisionDetector, YangReferenceResolver,
         implements YangLeavesHolder, YangDesc, YangReference, Parsable, CollisionDetector, YangReferenceResolver,
-        RpcNotificationContainer {
+        RpcNotificationContainer, YangFeatureHolder {
 
 
     private static final long serialVersionUID = 806201614L;
     private static final long serialVersionUID = 806201614L;
 
 
@@ -133,6 +133,11 @@ public class YangSubModule
     private List<YangLeafList> listOfLeafList;
     private List<YangLeafList> listOfLeafList;
 
 
     /**
     /**
+     * List of feature at root level in the module.
+     */
+    private List<YangFeature> listOfFeature;
+
+    /**
      * Organization owner of the sub-module.
      * Organization owner of the sub-module.
      */
      */
     private String organization;
     private String organization;
@@ -199,12 +204,18 @@ public class YangSubModule
     private List<YangResolutionInfo> usesResolutionList;
     private List<YangResolutionInfo> usesResolutionList;
 
 
     /**
     /**
+     * if-feature resolution list.
+     */
+    private List<YangResolutionInfo> ifFeatureResolutionList;
+
+    /**
      * Creates a sub module node.
      * Creates a sub module node.
      */
      */
     public YangSubModule() {
     public YangSubModule() {
         super(YangNodeType.SUB_MODULE_NODE);
         super(YangNodeType.SUB_MODULE_NODE);
         derivedTypeResolutionList = new LinkedList<>();
         derivedTypeResolutionList = new LinkedList<>();
         usesResolutionList = new LinkedList<>();
         usesResolutionList = new LinkedList<>();
+        ifFeatureResolutionList = new LinkedList<>();
         importList = new LinkedList<YangImport>();
         importList = new LinkedList<YangImport>();
         includeList = new LinkedList<YangInclude>();
         includeList = new LinkedList<YangInclude>();
         listOfLeaf = new LinkedList<YangLeaf>();
         listOfLeaf = new LinkedList<YangLeaf>();
@@ -538,8 +549,10 @@ public class YangSubModule
     public List<YangResolutionInfo> getUnresolvedResolutionList(ResolvableType type) {
     public List<YangResolutionInfo> getUnresolvedResolutionList(ResolvableType type) {
         if (type == ResolvableType.YANG_DERIVED_DATA_TYPE) {
         if (type == ResolvableType.YANG_DERIVED_DATA_TYPE) {
             return derivedTypeResolutionList;
             return derivedTypeResolutionList;
-        } else {
+        } else if (type == ResolvableType.YANG_USES) {
             return usesResolutionList;
             return usesResolutionList;
+        } else {
+            return ifFeatureResolutionList;
         }
         }
     }
     }
 
 
@@ -550,6 +563,8 @@ public class YangSubModule
             derivedTypeResolutionList.add(resolutionInfo);
             derivedTypeResolutionList.add(resolutionInfo);
         } else if (type == ResolvableType.YANG_USES) {
         } else if (type == ResolvableType.YANG_USES) {
             usesResolutionList.add(resolutionInfo);
             usesResolutionList.add(resolutionInfo);
+        } else if (type == ResolvableType.YANG_IF_FEATURE) {
+            ifFeatureResolutionList.add(resolutionInfo);
         }
         }
     }
     }
 
 
@@ -560,6 +575,8 @@ public class YangSubModule
             derivedTypeResolutionList = resolutionList;
             derivedTypeResolutionList = resolutionList;
         } else if (type == ResolvableType.YANG_USES) {
         } else if (type == ResolvableType.YANG_USES) {
             usesResolutionList = resolutionList;
             usesResolutionList = resolutionList;
+        } else if (type == ResolvableType.YANG_IF_FEATURE) {
+            ifFeatureResolutionList = resolutionList;
         }
         }
 
 
     }
     }
@@ -601,4 +618,22 @@ public class YangSubModule
             yangImport.addReferenceToImport(yangNodeSet);
             yangImport.addReferenceToImport(yangNodeSet);
         }
         }
     }
     }
+
+    @Override
+    public List<YangFeature> getFeatureList() {
+        return listOfFeature;
+    }
+
+    @Override
+    public void addFeatureList(YangFeature feature) {
+        if (getFeatureList() == null) {
+            setListOfFeature(new LinkedList<>());
+        }
+        getFeatureList().add(feature);
+    }
+
+    @Override
+    public void setListOfFeature(List<YangFeature> listOfFeature) {
+        this.listOfFeature = listOfFeature;
+    }
 }
 }

@@ -48,11 +48,11 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.getParent
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  *                | augment      | 7.15    | 0..1        | -child nodes     |
  *                | augment      | 7.15    | 0..1        | -child nodes     |
  *                | description  | 7.19.3  | 0..1        | -string          |
  *                | description  | 7.19.3  | 0..1        | -string          |
- *                | if-feature   | 7.18.2  | 0..n        | -TODO            |
+ *                | if-feature   | 7.18.2  | 0..n        | -YangIfFeature   |
  *                | refine       | 7.12.2  | 0..1        | -TODO            |
  *                | refine       | 7.12.2  | 0..1        | -TODO            |
  *                | reference    | 7.19.4  | 0..1        | -string          |
  *                | reference    | 7.19.4  | 0..1        | -string          |
  *                | status       | 7.19.2  | 0..1        | -YangStatus      |
  *                | status       | 7.19.2  | 0..1        | -YangStatus      |
- *                | when         | 7.19.5  | 0..1        | -TODO            |
+ *                | when         | 7.19.5  | 0..1        | -YangWhen        |
  *                +--------------+---------+-------------+------------------+
  *                +--------------+---------+-------------+------------------+
  */
  */
 
 
@@ -61,7 +61,8 @@ import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.getParent
  */
  */
 public class YangUses
 public class YangUses
         extends YangNode
         extends YangNode
-        implements YangCommonInfo, Parsable, Resolvable, CollisionDetector {
+        implements YangCommonInfo, Parsable, Resolvable, CollisionDetector, YangWhenHolder,
+        YangIfFeatureHolder {
 
 
     private static final long serialVersionUID = 806201617L;
     private static final long serialVersionUID = 806201617L;
 
 
@@ -91,6 +92,16 @@ public class YangUses
     private YangStatusType status;
     private YangStatusType status;
 
 
     /**
     /**
+     * When data of the node.
+     */
+    private YangWhen when;
+
+    /**
+     * List of if-feature.
+     */
+    private List<YangIfFeature> ifFeatureList;
+
+    /**
      * Status of resolution. If completely resolved enum value is "RESOLVED",
      * Status of resolution. If completely resolved enum value is "RESOLVED",
      * if not enum value is "UNRESOLVED", in case reference of grouping/typedef
      * if not enum value is "UNRESOLVED", in case reference of grouping/typedef
      * is added to uses/type but it's not resolved value of enum should be
      * is added to uses/type but it's not resolved value of enum should be
@@ -144,6 +155,26 @@ public class YangUses
     }
     }
 
 
     /**
     /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    @Override
+    public YangWhen getWhen() {
+        return when;
+    }
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    @Override
+    public void setWhen(YangWhen when) {
+        this.when = when;
+    }
+
+    /**
      * Returns the description.
      * Returns the description.
      *
      *
      * @return the description
      * @return the description
@@ -503,4 +534,22 @@ public class YangUses
     public List<List<YangLeafList>> getUsesResolvedListOfLeafList() {
     public List<List<YangLeafList>> getUsesResolvedListOfLeafList() {
         return resolvedGroupingLeafLists;
         return resolvedGroupingLeafLists;
     }
     }
+
+    @Override
+    public List<YangIfFeature> getIfFeatureList() {
+        return ifFeatureList;
+    }
+
+    @Override
+    public void addIfFeatureList(YangIfFeature ifFeature) {
+        if (getIfFeatureList() == null) {
+            setIfFeatureList(new LinkedList<>());
+        }
+        getIfFeatureList().add(ifFeature);
+    }
+
+    @Override
+    public void setIfFeatureList(List<YangIfFeature> ifFeatureList) {
+        this.ifFeatureList = ifFeatureList;
+    }
 }
 }

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.yangutils.datamodel;
+
+import java.io.Serializable;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
+import org.onosproject.yangutils.datamodel.utils.YangConstructType;
+
+/*
+ * Reference RFC 6020.
+ *
+ * The "when" statement makes its parent data definition statement
+ * conditional.  The node defined by the parent data definition
+ * statement is only valid when the condition specified by the "when"
+ * statement is satisfied.
+ *
+ * The statement's argument is an XPath expression, which is used to formally
+ * specify this condition.  If the XPath  expression conceptually evaluates to
+ * "true" for a particular instance, then the node defined by the parent data
+ * definition statement is valid; otherwise, it is not.
+ *
+ *  The when's sub-statements
+ *
+ *                +---------------+---------+-------------+------------------+
+ *                | substatement  | section | cardinality |data model mapping|
+ *                +---------------+---------+-------------+------------------+
+ *                | description   | 7.19.3  | 0..1        | -string          |
+ *                | reference     | 7.19.4  | 0..1        | -string          |
+ *                +---------------+---------+-------------+------------------+
+ */
+
+/**
+ * Represents information defined in YANG when.
+ */
+public class YangWhen implements YangDesc, YangReference, Parsable, Serializable {
+
+    private static final long serialVersionUID = 806201646L;
+
+    /**
+     * When condition info.
+     */
+    private String condition;
+
+    /**
+     * Description string.
+     */
+    private String description;
+
+    /**
+     * Reference string.
+     */
+    private String reference;
+
+    /**
+     * Creates a YANG when restriction.
+     */
+    public YangWhen() {
+    }
+
+    /**
+     * Returns the condition.
+     *
+     * @return the condition
+     */
+    public String getCondition() {
+        return condition;
+    }
+
+    /**
+     * Sets the condition.
+     *
+     * @param condition the condition to set
+     */
+    public void setCondition(String condition) {
+        this.condition = condition;
+    }
+
+    /**
+     * Returns the description.
+     *
+     * @return the description
+     */
+    @Override
+    public String getDescription() {
+        return description;
+    }
+
+    /**
+     * Sets the description.
+     *
+     * @param description set the description
+     */
+    @Override
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    /**
+     * Returns the textual reference.
+     *
+     * @return the reference
+     */
+    @Override
+    public String getReference() {
+        return reference;
+    }
+
+    /**
+     * Sets the textual reference.
+     *
+     * @param reference the reference to set
+     */
+    @Override
+    public void setReference(String reference) {
+        this.reference = reference;
+    }
+
+    /**
+     * Returns the type of the parsed data.
+     *
+     * @return returns WHEN_DATA
+     */
+    @Override
+    public YangConstructType getYangConstructType() {
+        return YangConstructType.WHEN_DATA;
+    }
+
+    /**
+     * Validates the data on entering the corresponding parse tree node.
+     *
+     * @throws DataModelException a violation of data model rules
+     */
+    @Override
+    public void validateDataOnEntry() throws DataModelException {
+        // TODO auto-generated method stub, to be implemented by parser
+    }
+
+    /**
+     * Validates the data on exiting the corresponding parse tree node.
+     *
+     * @throws DataModelException a violation of data model rules
+     */
+    @Override
+    public void validateDataOnExit() throws DataModelException {
+        // TODO auto-generated method stub, to be implemented by parser
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.datamodel;
+
+/**
+ * Abstraction of when entity. It is used to abstract the data holders of when.
+ */
+public interface YangWhenHolder {
+
+    /**
+     * Returns the when.
+     *
+     * @return the when
+     */
+    YangWhen getWhen();
+
+    /**
+     * Sets the when.
+     *
+     * @param when the when to set
+     */
+    void setWhen(YangWhen when);
+}

@@ -21,6 +21,7 @@ import java.util.Set;
 
 
 import org.onosproject.yangutils.datamodel.CollisionDetector;
 import org.onosproject.yangutils.datamodel.CollisionDetector;
 import org.onosproject.yangutils.datamodel.ResolvableType;
 import org.onosproject.yangutils.datamodel.ResolvableType;
+import org.onosproject.yangutils.datamodel.YangIfFeature;
 import org.onosproject.yangutils.datamodel.YangLeaf;
 import org.onosproject.yangutils.datamodel.YangLeaf;
 import org.onosproject.yangutils.datamodel.YangLeafList;
 import org.onosproject.yangutils.datamodel.YangLeafList;
 import org.onosproject.yangutils.datamodel.YangLeavesHolder;
 import org.onosproject.yangutils.datamodel.YangLeavesHolder;
@@ -29,13 +30,14 @@ import org.onosproject.yangutils.datamodel.YangReferenceResolver;
 import org.onosproject.yangutils.datamodel.YangResolutionInfo;
 import org.onosproject.yangutils.datamodel.YangResolutionInfo;
 import org.onosproject.yangutils.datamodel.YangRpc;
 import org.onosproject.yangutils.datamodel.YangRpc;
 import org.onosproject.yangutils.datamodel.YangType;
 import org.onosproject.yangutils.datamodel.YangType;
+import org.onosproject.yangutils.datamodel.YangUses;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 
 
-
 /**
 /**
  * Represents utilities for data model tree.
  * Represents utilities for data model tree.
  */
  */
 public final class DataModelUtils {
 public final class DataModelUtils {
+
     /**
     /**
      * Creates a new data model tree utility.
      * Creates a new data model tree utility.
      */
      */
@@ -161,11 +163,15 @@ public final class DataModelUtils {
                 .getEntityToResolve() instanceof YangType) {
                 .getEntityToResolve() instanceof YangType) {
             resolutionNode.addToResolutionList(resolutionInfo,
             resolutionNode.addToResolutionList(resolutionInfo,
                     ResolvableType.YANG_DERIVED_DATA_TYPE);
                     ResolvableType.YANG_DERIVED_DATA_TYPE);
-        } else {
+        } else if (resolutionInfo.getEntityToResolveInfo()
+                .getEntityToResolve() instanceof YangUses) {
             resolutionNode.addToResolutionList(resolutionInfo,
             resolutionNode.addToResolutionList(resolutionInfo,
                     ResolvableType.YANG_USES);
                     ResolvableType.YANG_USES);
+        } else if (resolutionInfo.getEntityToResolveInfo()
+                .getEntityToResolve() instanceof YangIfFeature) {
+            resolutionNode.addToResolutionList(resolutionInfo,
+                    ResolvableType.YANG_IF_FEATURE);
         }
         }
-
     }
     }
 
 
     /**
     /**

@@ -46,6 +46,11 @@ public enum ResolvableStatus {
      * Identifies that resolvable entity is inter file linked (i.e. complete
      * Identifies that resolvable entity is inter file linked (i.e. complete
      * linking with external files).
      * linking with external files).
      */
      */
-    INTER_FILE_LINKED
+    INTER_FILE_LINKED,
+
+    /**
+     * Identifies that resolvable entity is referred node is not defined.
+     */
+    UNDEFINED
 
 
 }
 }

@@ -18,6 +18,7 @@ package org.onosproject.yangutils.linker.impl;
 import java.io.Serializable;
 import java.io.Serializable;
 
 
 import org.onosproject.yangutils.datamodel.YangEntityToResolveInfo;
 import org.onosproject.yangutils.datamodel.YangEntityToResolveInfo;
+import org.onosproject.yangutils.datamodel.YangIfFeature;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangType;
 import org.onosproject.yangutils.datamodel.YangType;
 import org.onosproject.yangutils.datamodel.YangUses;
 import org.onosproject.yangutils.datamodel.YangUses;
@@ -76,6 +77,8 @@ public class YangEntityToResolveInfoImpl<T> implements YangEntityToResolveInfo<T
             prefix = ((YangType<?>) entityToBeResolved).getPrefix();
             prefix = ((YangType<?>) entityToBeResolved).getPrefix();
         } else if (entityToBeResolved instanceof YangUses) {
         } else if (entityToBeResolved instanceof YangUses) {
             prefix = ((YangUses) entityToBeResolved).getPrefix();
             prefix = ((YangUses) entityToBeResolved).getPrefix();
+        } else if (entityToBeResolved instanceof YangIfFeature) {
+            prefix = ((YangIfFeature) entityToBeResolved).getPrefix();
         } else {
         } else {
             throw new LinkerException("Linker Exception: Entity to resolved is other than type/uses");
             throw new LinkerException("Linker Exception: Entity to resolved is other than type/uses");
         }
         }

@@ -156,6 +156,8 @@ public class YangLinkerManager
             throws LinkerException {
             throws LinkerException {
         for (YangNode yangNode : yangNodeSet) {
         for (YangNode yangNode : yangNodeSet) {
             try {
             try {
+                ((YangReferenceResolver) yangNode)
+                        .resolveInterFileLinking(ResolvableType.YANG_IF_FEATURE);
                 ((YangReferenceResolver) yangNode).resolveInterFileLinking(ResolvableType.YANG_USES);
                 ((YangReferenceResolver) yangNode).resolveInterFileLinking(ResolvableType.YANG_USES);
                 ((YangReferenceResolver) yangNode)
                 ((YangReferenceResolver) yangNode)
                         .resolveInterFileLinking(ResolvableType.YANG_DERIVED_DATA_TYPE);
                         .resolveInterFileLinking(ResolvableType.YANG_DERIVED_DATA_TYPE);

@@ -17,15 +17,22 @@
 package org.onosproject.yangutils.linker.impl;
 package org.onosproject.yangutils.linker.impl;
 
 
 import java.io.Serializable;
 import java.io.Serializable;
+import java.util.Iterator;
+import java.util.List;
 import java.util.Stack;
 import java.util.Stack;
 
 
 import org.onosproject.yangutils.datamodel.Resolvable;
 import org.onosproject.yangutils.datamodel.Resolvable;
 import org.onosproject.yangutils.datamodel.YangDataTypes;
 import org.onosproject.yangutils.datamodel.YangDataTypes;
 import org.onosproject.yangutils.datamodel.YangDerivedInfo;
 import org.onosproject.yangutils.datamodel.YangDerivedInfo;
+import org.onosproject.yangutils.datamodel.YangEntityToResolveInfo;
+import org.onosproject.yangutils.datamodel.YangFeature;
+import org.onosproject.yangutils.datamodel.YangFeatureHolder;
 import org.onosproject.yangutils.datamodel.YangGrouping;
 import org.onosproject.yangutils.datamodel.YangGrouping;
+import org.onosproject.yangutils.datamodel.YangIfFeature;
 import org.onosproject.yangutils.datamodel.YangImport;
 import org.onosproject.yangutils.datamodel.YangImport;
 import org.onosproject.yangutils.datamodel.YangInclude;
 import org.onosproject.yangutils.datamodel.YangInclude;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNodeIdentifier;
 import org.onosproject.yangutils.datamodel.YangReferenceResolver;
 import org.onosproject.yangutils.datamodel.YangReferenceResolver;
 import org.onosproject.yangutils.datamodel.YangResolutionInfo;
 import org.onosproject.yangutils.datamodel.YangResolutionInfo;
 import org.onosproject.yangutils.datamodel.YangType;
 import org.onosproject.yangutils.datamodel.YangType;
@@ -39,9 +46,11 @@ import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.INTER_F
 import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.INTRA_FILE_RESOLVED;
 import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.INTRA_FILE_RESOLVED;
 import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.LINKED;
 import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.LINKED;
 import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.RESOLVED;
 import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.RESOLVED;
+import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.UNDEFINED;
 import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.UNRESOLVED;
 import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.UNRESOLVED;
 import static org.onosproject.yangutils.linker.YangLinkingPhase.INTER_FILE;
 import static org.onosproject.yangutils.linker.YangLinkingPhase.INTER_FILE;
 import static org.onosproject.yangutils.linker.YangLinkingPhase.INTRA_FILE;
 import static org.onosproject.yangutils.linker.YangLinkingPhase.INTRA_FILE;
+import static org.onosproject.yangutils.utils.UtilConstants.FEATURE_LINKER_ERROR;
 import static org.onosproject.yangutils.utils.UtilConstants.GROUPING_LINKER_ERROR;
 import static org.onosproject.yangutils.utils.UtilConstants.GROUPING_LINKER_ERROR;
 import static org.onosproject.yangutils.utils.UtilConstants.TYPEDEF_LINKER_ERROR;
 import static org.onosproject.yangutils.utils.UtilConstants.TYPEDEF_LINKER_ERROR;
 
 
@@ -64,7 +73,7 @@ public class YangResolutionInfoImpl<T>
     /**
     /**
      * Error line number.
      * Error line number.
      */
      */
-    private  transient int lineNumber;
+    private transient int lineNumber;
 
 
     /**
     /**
      * Error character position in number.
      * Error character position in number.
@@ -115,7 +124,7 @@ public class YangResolutionInfoImpl<T>
 
 
         setCurReferenceResolver(dataModelRootNode);
         setCurReferenceResolver(dataModelRootNode);
 
 
-        // Current node to resolve, it can be a YANG type or YANG uses.
+        // Current node to resolve, it can be a YANG type, YANG uses or YANG if-feature.
         T entityToResolve = getEntityToResolveInfo().getEntityToResolve();
         T entityToResolve = getEntityToResolveInfo().getEntityToResolve();
 
 
         // Check if linking is already done
         // Check if linking is already done
@@ -128,7 +137,8 @@ public class YangResolutionInfoImpl<T>
                 return;
                 return;
             }
             }
         } else {
         } else {
-            throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
+            throw new DataModelException("Data Model Exception: Entity to resolved is other than " +
+                    "type/uses/if-feature");
         }
         }
 
 
         // Push the initial entity to resolve in stack.
         // Push the initial entity to resolve in stack.
@@ -154,57 +164,60 @@ public class YangResolutionInfoImpl<T>
 
 
                 Resolvable resolvable = (Resolvable) entityToResolve;
                 Resolvable resolvable = (Resolvable) entityToResolve;
                 switch (resolvable.getResolvableStatus()) {
                 switch (resolvable.getResolvableStatus()) {
-                case RESOLVED: {
-                    /*
-                     * If the entity is already resolved in the stack, then pop
-                     * it and continue with the remaining stack elements to
-                     * resolve
-                     */
-                    getPartialResolvedStack().pop();
-                    break;
-                }
+                    case RESOLVED: {
+                        /*
+                         * If the entity is already resolved in the stack, then pop
+                         * it and continue with the remaining stack elements to
+                         * resolve
+                         */
+                        getPartialResolvedStack().pop();
+                        break;
+                    }
 
 
-                case LINKED: {
-                    /*
-                     * If the top of the stack is already linked then resolve
-                     * the references and pop the entity and continue with
-                     * remaining stack elements to resolve.
-                     */
-                    resolveTopOfStack(INTRA_FILE);
-                    getPartialResolvedStack().pop();
-                    break;
-                }
+                    case LINKED: {
+                        /*
+                         * If the top of the stack is already linked then resolve
+                         * the references and pop the entity and continue with
+                         * remaining stack elements to resolve.
+                         */
+                        resolveTopOfStack(INTRA_FILE);
+                        getPartialResolvedStack().pop();
+                        break;
+                    }
 
 
-                case INTRA_FILE_RESOLVED: {
-                    /*
-                     * Pop the top of the stack.
-                     */
-                    getPartialResolvedStack().pop();
-                    break;
-                }
+                    case INTRA_FILE_RESOLVED: {
+                        /*
+                         * Pop the top of the stack.
+                         */
+                        getPartialResolvedStack().pop();
+                        break;
+                    }
 
 
-                case UNRESOLVED: {
-                    linkTopOfStackReferenceUpdateStack();
-
-                    if (resolvable.getResolvableStatus() == UNRESOLVED) {
-                        // If current entity is still not resolved, then
-                        // linking/resolution has failed.
-                        String errorInfo;
-                        if (resolvable instanceof YangType) {
-                            errorInfo = TYPEDEF_LINKER_ERROR;
-                        } else {
-                            errorInfo = GROUPING_LINKER_ERROR;
+                    case UNRESOLVED: {
+                        linkTopOfStackReferenceUpdateStack();
+
+                        if (resolvable.getResolvableStatus() == UNRESOLVED) {
+                            // If current entity is still not resolved, then
+                            // linking/resolution has failed.
+                            String errorInfo;
+                            if (resolvable instanceof YangType) {
+                                errorInfo = TYPEDEF_LINKER_ERROR;
+                            } else if (resolvable instanceof YangUses) {
+                                errorInfo = GROUPING_LINKER_ERROR;
+                            } else {
+                                errorInfo = FEATURE_LINKER_ERROR;
+                            }
+                            DataModelException dataModelException =
+                                    new DataModelException(errorInfo);
+                            dataModelException.setLine(getLineNumber());
+                            dataModelException.setCharPosition(getCharPosition());
+                            throw dataModelException;
                         }
                         }
-                        DataModelException dataModelException = new DataModelException(errorInfo);
-                        dataModelException.setLine(getLineNumber());
-                        dataModelException.setCharPosition(getCharPosition());
-                        throw dataModelException;
+                        break;
+                    }
+                    default: {
+                        throw new DataModelException("Data Model Exception: Unsupported, linker state");
                     }
                     }
-                    break;
-                }
-                default: {
-                    throw new DataModelException("Data Model Exception: Unsupported, linker state");
-                }
 
 
                 }
                 }
 
 
@@ -222,8 +235,9 @@ public class YangResolutionInfoImpl<T>
     private void resolveTopOfStack(YangLinkingPhase linkingPhase)
     private void resolveTopOfStack(YangLinkingPhase linkingPhase)
             throws DataModelException {
             throws DataModelException {
         ((Resolvable) getCurrentEntityToResolveFromStack()).resolve();
         ((Resolvable) getCurrentEntityToResolveFromStack()).resolve();
-        if (((Resolvable) getCurrentEntityToResolveFromStack()).getResolvableStatus() != INTRA_FILE_RESOLVED) {
-            // Sets the resolution status in inside the type/uses.
+        if (((Resolvable) getCurrentEntityToResolveFromStack()).getResolvableStatus() != INTRA_FILE_RESOLVED
+                && ((Resolvable) getCurrentEntityToResolveFromStack()).getResolvableStatus() != UNDEFINED) {
+            // Sets the resolution status in inside the type/uses/if-feature.
             ((Resolvable) getCurrentEntityToResolveFromStack()).setResolvableStatus(RESOLVED);
             ((Resolvable) getCurrentEntityToResolveFromStack()).setResolvableStatus(RESOLVED);
         }
         }
     }
     }
@@ -253,21 +267,61 @@ public class YangResolutionInfoImpl<T>
         YangNode potentialAncestorWithReferredNode = getPartialResolvedStack().peek()
         YangNode potentialAncestorWithReferredNode = getPartialResolvedStack().peek()
                 .getHolderOfEntityToResolve();
                 .getHolderOfEntityToResolve();
 
 
-        /**
-         * Traverse up in the ancestor tree to check if the referred node is
-         * defined
-         */
-        while (potentialAncestorWithReferredNode != null) {
+        if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+            resolveSelfFileLinkingForIfFeature(potentialAncestorWithReferredNode);
+            return;
+        } else {
 
 
             /**
             /**
-             * Check for the referred node defined in a ancestor scope
+             * Traverse up in the ancestor tree to check if the referred node is
+             * defined
              */
              */
-            YangNode potentialReferredNode = potentialAncestorWithReferredNode.getChild();
-            if (isReferredNodeInSiblingListProcessed(potentialReferredNode)) {
-                return;
+            while (potentialAncestorWithReferredNode != null) {
+
+                /**
+                 * Check for the referred node defined in a ancestor scope
+                 */
+                YangNode potentialReferredNode = potentialAncestorWithReferredNode.getChild();
+                if (isReferredNodeInSiblingListProcessed(potentialReferredNode)) {
+                    return;
+                }
+
+                potentialAncestorWithReferredNode = potentialAncestorWithReferredNode.getParent();
             }
             }
+        }
 
 
-            potentialAncestorWithReferredNode = potentialAncestorWithReferredNode.getParent();
+        /*
+         * In case prefix is not present it's a candidate for inter-file
+         * resolution via include list.
+         */
+        if (getRefPrefix() == null) {
+            ((Resolvable) getCurrentEntityToResolveFromStack()).setResolvableStatus(INTRA_FILE_RESOLVED);
+        }
+    }
+
+    /**
+     * Resolves self file linking for if-feature.
+     *
+     * @param potentialAncestorWithReferredNode if-feature holder node
+     * @throws DataModelException DataModelException a violation of data model
+     *                            rules
+     */
+    private void resolveSelfFileLinkingForIfFeature(YangNode potentialAncestorWithReferredNode)
+            throws DataModelException {
+
+        YangFeatureHolder featureHolder = getFeatureHolder(potentialAncestorWithReferredNode);
+        YangNode potentialReferredNode = (YangNode) featureHolder;
+        if (isReferredNode(potentialReferredNode)) {
+
+            // Adds reference link of entity to the node under resolution.
+            addReferredEntityLink(potentialReferredNode, LINKED);
+
+            /**
+             * resolve the reference and update the partial resolution stack
+             * with any further recursive references
+             */
+            addUnresolvedRecursiveReferenceToStack(potentialReferredNode);
+            return;
         }
         }
 
 
         /*
         /*
@@ -279,6 +333,22 @@ public class YangResolutionInfoImpl<T>
         }
         }
     }
     }
 
 
+
+    /**
+     * Returns feature holder(module/sub-module node) .
+     *
+     * @param potentialAncestorWithReferredNode if-feature holder node
+     */
+    private YangFeatureHolder getFeatureHolder(YangNode potentialAncestorWithReferredNode) {
+        while (potentialAncestorWithReferredNode != null) {
+            if (potentialAncestorWithReferredNode instanceof YangFeatureHolder) {
+                return (YangFeatureHolder) potentialAncestorWithReferredNode;
+            }
+            potentialAncestorWithReferredNode = potentialAncestorWithReferredNode.getParent();
+        }
+        return null;
+    }
+
     /**
     /**
      * Checks if the reference in self file or in external file.
      * Checks if the reference in self file or in external file.
      *
      *
@@ -352,6 +422,14 @@ public class YangResolutionInfoImpl<T>
                  */
                  */
                 return isNodeNameSameAsResolutionInfoName(potentialReferredNode);
                 return isNodeNameSameAsResolutionInfoName(potentialReferredNode);
             }
             }
+        } else if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+            if (potentialReferredNode instanceof YangFeatureHolder) {
+                /*
+                 * Check if name of node name matches with the entity being
+                 * resolved
+                 */
+                return isNodeNameSameAsResolutionInfoName(potentialReferredNode);
+            }
         } else {
         } else {
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
         }
         }
@@ -381,12 +459,31 @@ public class YangResolutionInfoImpl<T>
                     ((YangUses) getCurrentEntityToResolveFromStack()).getName())) {
                     ((YangUses) getCurrentEntityToResolveFromStack()).getName())) {
                 return true;
                 return true;
             }
             }
+        } else if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+            return isFeatureDefinedInNode(node);
         } else {
         } else {
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
         }
         }
         return false;
         return false;
     }
     }
 
 
+    private boolean isFeatureDefinedInNode(YangNode node) throws DataModelException {
+        YangNodeIdentifier ifFeature = ((YangIfFeature) getCurrentEntityToResolveFromStack()).getName();
+        List<YangFeature> featureList = ((YangFeatureHolder) node).getFeatureList();
+        if (featureList != null && !featureList.isEmpty()) {
+            Iterator<YangFeature> iterator = featureList.iterator();
+            while (iterator.hasNext()) {
+                YangFeature feature = iterator.next();
+                if (ifFeature.getName().equals(feature.getName())) {
+                    ((YangIfFeature) getCurrentEntityToResolveFromStack()).setReferredFeature(feature);
+                    ((YangIfFeature) getCurrentEntityToResolveFromStack()).setReferredFeatureHolder(node);
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
     /**
     /**
      * Adds reference of grouping/typedef in uses/type.
      * Adds reference of grouping/typedef in uses/type.
      *
      *
@@ -403,6 +500,8 @@ public class YangResolutionInfoImpl<T>
         } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
         } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
             ((YangUses) getCurrentEntityToResolveFromStack())
             ((YangUses) getCurrentEntityToResolveFromStack())
                     .setRefGroup((YangGrouping) referredNode);
                     .setRefGroup((YangGrouping) referredNode);
+        } else if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+            // do nothing , referred node is already set
         } else {
         } else {
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
         }
         }
@@ -440,6 +539,8 @@ public class YangResolutionInfoImpl<T>
              * return true, else return false.
              * return true, else return false.
              */
              */
             addUnResolvedUsesToStack(referredNode);
             addUnResolvedUsesToStack(referredNode);
+        } else if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+            addUnResolvedIfFeatureToStack(referredNode);
         } else {
         } else {
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
         }
         }
@@ -469,6 +570,26 @@ public class YangResolutionInfoImpl<T>
     }
     }
 
 
     /**
     /**
+     * Returns if there is any unresolved if-feature in feature.
+     *
+     * @param node module/submodule node
+     */
+    private void addUnResolvedIfFeatureToStack(YangNode node) {
+        YangFeature refFeature = ((YangIfFeature) getCurrentEntityToResolveFromStack()).getReferredFeature();
+        List<YangIfFeature> ifFeatureList = refFeature.getIfFeatureList();
+        if (ifFeatureList != null && !ifFeatureList.isEmpty()) {
+            Iterator<YangIfFeature> ifFeatureIterator = ifFeatureList.iterator();
+            while (ifFeatureIterator.hasNext()) {
+                YangIfFeature ifFeature = ifFeatureIterator.next();
+                YangEntityToResolveInfo<YangIfFeature> unResolvedEntityInfo = new YangEntityToResolveInfoImpl<>();
+                unResolvedEntityInfo.setEntityToResolve(ifFeature);
+                unResolvedEntityInfo.setHolderOfEntityToResolve(node);
+                addInPartialResolvedStack((YangEntityToResolveInfoImpl<T>) unResolvedEntityInfo);
+            }
+        }
+    }
+
+    /**
      * Returns stack of YANG type with partially resolved YANG construct
      * Returns stack of YANG type with partially resolved YANG construct
      * hierarchy.
      * hierarchy.
      *
      *
@@ -600,6 +721,8 @@ public class YangResolutionInfoImpl<T>
             refPrefix = ((YangType<?>) getCurrentEntityToResolveFromStack()).getPrefix();
             refPrefix = ((YangType<?>) getCurrentEntityToResolveFromStack()).getPrefix();
         } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
         } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
             refPrefix = ((YangUses) getCurrentEntityToResolveFromStack()).getPrefix();
             refPrefix = ((YangUses) getCurrentEntityToResolveFromStack()).getPrefix();
+        } else if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+            refPrefix = ((YangIfFeature) getCurrentEntityToResolveFromStack()).getPrefix();
         } else {
         } else {
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
         }
         }
@@ -623,41 +746,50 @@ public class YangResolutionInfoImpl<T>
 
 
                 Resolvable resolvable = (Resolvable) entityToResolve;
                 Resolvable resolvable = (Resolvable) entityToResolve;
                 switch (resolvable.getResolvableStatus()) {
                 switch (resolvable.getResolvableStatus()) {
-                case RESOLVED: {
-                    /*
-                     * If the entity is already resolved in the stack, then pop
-                     * it and continue with the remaining stack elements to
-                     * resolve
-                     */
-                    getPartialResolvedStack().pop();
-                    break;
-                }
+                    case RESOLVED: {
+                        /*
+                         * If the entity is already resolved in the stack, then pop
+                         * it and continue with the remaining stack elements to
+                         * resolve
+                         */
+                        getPartialResolvedStack().pop();
+                        break;
+                    }
 
 
-                case INTER_FILE_LINKED: {
-                    /*
-                     * If the top of the stack is already linked then resolve
-                     * the references and pop the entity and continue with
-                     * remaining stack elements to resolve
-                     */
-                    resolveTopOfStack(INTER_FILE);
-                    getPartialResolvedStack().pop();
-                    break;
-                }
+                    case INTER_FILE_LINKED: {
+                        /*
+                         * If the top of the stack is already linked then resolve
+                         * the references and pop the entity and continue with
+                         * remaining stack elements to resolve
+                         */
+                        resolveTopOfStack(INTER_FILE);
+                        getPartialResolvedStack().pop();
+                        break;
+                    }
 
 
-                case INTRA_FILE_RESOLVED: {
-                    /*
-                     * If the top of the stack is intra file resolved then check
-                     * if top of stack is linked, if not link it using
-                     * import/include list and push the linked referred entity
-                     * to the stack, otherwise only push it to the stack.
-                     */
-                    linkInterFileTopOfStackRefUpdateStack();
-                    break;
-                }
+                    case INTRA_FILE_RESOLVED: {
+                        /*
+                         * If the top of the stack is intra file resolved then check
+                         * if top of stack is linked, if not link it using
+                         * import/include list and push the linked referred entity
+                         * to the stack, otherwise only push it to the stack.
+                         */
+                        linkInterFileTopOfStackRefUpdateStack();
+                        break;
+                    }
 
 
-                default: {
-                    throw new DataModelException("Data Model Exception: Unsupported, linker state");
-                }
+                    case UNDEFINED: {
+                        /*
+                         * In case of if-feature resolution, if referred "feature" is not
+                         * defined then the resolvable status will be undefined.
+                         */
+                        getPartialResolvedStack().pop();
+                        break;
+                    }
+
+                    default: {
+                        throw new DataModelException("Data Model Exception: Unsupported, linker state");
+                    }
 
 
                 }
                 }
 
 
@@ -701,6 +833,11 @@ public class YangResolutionInfoImpl<T>
                     return;
                     return;
                 }
                 }
             }
             }
+
+            if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+                ((YangIfFeature) getCurrentEntityToResolveFromStack()).setResolvableStatus(UNDEFINED);
+                return;
+            }
             // Exception when referred typedef/grouping is not found.
             // Exception when referred typedef/grouping is not found.
             DataModelException dataModelException = new DataModelException("YANG file error: Referred " +
             DataModelException dataModelException = new DataModelException("YANG file error: Referred " +
                     "typedef/grouping for a given type/uses can't be found.");
                     "typedef/grouping for a given type/uses can't be found.");
@@ -735,6 +872,8 @@ public class YangResolutionInfoImpl<T>
                 linkedNode = findRefTypedef(yangInclude.getIncludedNode());
                 linkedNode = findRefTypedef(yangInclude.getIncludedNode());
             } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
             } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
                 linkedNode = findRefGrouping(yangInclude.getIncludedNode());
                 linkedNode = findRefGrouping(yangInclude.getIncludedNode());
+            } else if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+                linkedNode = findRefFeature(yangInclude.getIncludedNode());
             }
             }
             if (linkedNode != null) {
             if (linkedNode != null) {
                 // Add the link to external entity.
                 // Add the link to external entity.
@@ -776,6 +915,8 @@ public class YangResolutionInfoImpl<T>
                     linkedNode = findRefTypedef(yangImport.getImportedNode());
                     linkedNode = findRefTypedef(yangImport.getImportedNode());
                 } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
                 } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
                     linkedNode = findRefGrouping(yangImport.getImportedNode());
                     linkedNode = findRefGrouping(yangImport.getImportedNode());
+                } else if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+                    linkedNode = findRefFeature(yangImport.getImportedNode());
                 }
                 }
                 if (linkedNode != null) {
                 if (linkedNode != null) {
                     // Add the link to external entity.
                     // Add the link to external entity.
@@ -816,6 +957,8 @@ public class YangResolutionInfoImpl<T>
             return (T) derivedInfo.getReferredTypeDef();
             return (T) derivedInfo.getReferredTypeDef();
         } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
         } else if (getCurrentEntityToResolveFromStack() instanceof YangUses) {
             return (T) ((YangUses) getCurrentEntityToResolveFromStack()).getRefGroup();
             return (T) ((YangUses) getCurrentEntityToResolveFromStack()).getRefGroup();
+        } else if (getCurrentEntityToResolveFromStack() instanceof YangIfFeature) {
+            return (T) ((YangIfFeature) getCurrentEntityToResolveFromStack()).getReferredFeatureHolder();
         } else {
         } else {
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
             throw new DataModelException("Data Model Exception: Entity to resolved is other than type/uses");
         }
         }
@@ -842,6 +985,29 @@ public class YangResolutionInfoImpl<T>
     }
     }
 
 
     /**
     /**
+     * Finds the referred feature node at the root level of imported/included node.
+     *
+     * @param refNode module/sub-module node
+     * @return referred feature
+     */
+    private YangNode findRefFeature(YangNode refNode) {
+        YangNodeIdentifier ifFeature = ((YangIfFeature) getCurrentEntityToResolveFromStack()).getName();
+        List<YangFeature> featureList = ((YangFeatureHolder) refNode).getFeatureList();
+
+        if (featureList != null && !featureList.isEmpty()) {
+            Iterator<YangFeature> iterator = featureList.iterator();
+            while (iterator.hasNext()) {
+                YangFeature feature = iterator.next();
+                if (ifFeature.getName().equals(feature.getName())) {
+                    ((YangIfFeature) getCurrentEntityToResolveFromStack()).setReferredFeature(feature);
+                    return refNode;
+                }
+            }
+        }
+        return null;
+    }
+
+    /**
      * Finds the referred typedef node at the root level of imported/included node.
      * Finds the referred typedef node at the root level of imported/included node.
      *
      *
      * @param refNode module/sub-module node
      * @param refNode module/sub-module node

@@ -40,7 +40,9 @@ import org.onosproject.yangutils.parser.impl.listeners.DefaultListener;
 import org.onosproject.yangutils.parser.impl.listeners.DescriptionListener;
 import org.onosproject.yangutils.parser.impl.listeners.DescriptionListener;
 import org.onosproject.yangutils.parser.impl.listeners.EnumListener;
 import org.onosproject.yangutils.parser.impl.listeners.EnumListener;
 import org.onosproject.yangutils.parser.impl.listeners.EnumerationListener;
 import org.onosproject.yangutils.parser.impl.listeners.EnumerationListener;
+import org.onosproject.yangutils.parser.impl.listeners.FeatureListener;
 import org.onosproject.yangutils.parser.impl.listeners.GroupingListener;
 import org.onosproject.yangutils.parser.impl.listeners.GroupingListener;
+import org.onosproject.yangutils.parser.impl.listeners.IfFeatureListener;
 import org.onosproject.yangutils.parser.impl.listeners.ImportListener;
 import org.onosproject.yangutils.parser.impl.listeners.ImportListener;
 import org.onosproject.yangutils.parser.impl.listeners.IncludeListener;
 import org.onosproject.yangutils.parser.impl.listeners.IncludeListener;
 import org.onosproject.yangutils.parser.impl.listeners.InputListener;
 import org.onosproject.yangutils.parser.impl.listeners.InputListener;
@@ -53,6 +55,7 @@ import org.onosproject.yangutils.parser.impl.listeners.MandatoryListener;
 import org.onosproject.yangutils.parser.impl.listeners.MaxElementsListener;
 import org.onosproject.yangutils.parser.impl.listeners.MaxElementsListener;
 import org.onosproject.yangutils.parser.impl.listeners.MinElementsListener;
 import org.onosproject.yangutils.parser.impl.listeners.MinElementsListener;
 import org.onosproject.yangutils.parser.impl.listeners.ModuleListener;
 import org.onosproject.yangutils.parser.impl.listeners.ModuleListener;
+import org.onosproject.yangutils.parser.impl.listeners.MustListener;
 import org.onosproject.yangutils.parser.impl.listeners.NotificationListener;
 import org.onosproject.yangutils.parser.impl.listeners.NotificationListener;
 import org.onosproject.yangutils.parser.impl.listeners.NamespaceListener;
 import org.onosproject.yangutils.parser.impl.listeners.NamespaceListener;
 import org.onosproject.yangutils.parser.impl.listeners.OrganizationListener;
 import org.onosproject.yangutils.parser.impl.listeners.OrganizationListener;
@@ -76,6 +79,7 @@ import org.onosproject.yangutils.parser.impl.listeners.UnitsListener;
 import org.onosproject.yangutils.parser.impl.listeners.UsesListener;
 import org.onosproject.yangutils.parser.impl.listeners.UsesListener;
 import org.onosproject.yangutils.parser.impl.listeners.ValueListener;
 import org.onosproject.yangutils.parser.impl.listeners.ValueListener;
 import org.onosproject.yangutils.parser.impl.listeners.VersionListener;
 import org.onosproject.yangutils.parser.impl.listeners.VersionListener;
+import org.onosproject.yangutils.parser.impl.listeners.WhenListener;
 
 
 import static org.onosproject.yangutils.utils.UtilConstants.UNSUPPORTED_YANG_CONSTRUCT;
 import static org.onosproject.yangutils.utils.UtilConstants.UNSUPPORTED_YANG_CONSTRUCT;
 import static org.onosproject.yangutils.utils.UtilConstants.CURRENTLY_UNSUPPORTED;
 import static org.onosproject.yangutils.utils.UtilConstants.CURRENTLY_UNSUPPORTED;
@@ -473,22 +477,22 @@ public class TreeWalkListener implements GeneratedYangListener {
 
 
     @Override
     @Override
     public void enterFeatureStatement(GeneratedYangParser.FeatureStatementContext ctx) {
     public void enterFeatureStatement(GeneratedYangParser.FeatureStatementContext ctx) {
-        handleUnsupportedYangConstruct(YangConstructType.FEATURE_DATA, ctx, CURRENTLY_UNSUPPORTED);
+        FeatureListener.processFeatureEntry(this, ctx);
     }
     }
 
 
     @Override
     @Override
     public void exitFeatureStatement(GeneratedYangParser.FeatureStatementContext ctx) {
     public void exitFeatureStatement(GeneratedYangParser.FeatureStatementContext ctx) {
-        //TODO: to be implemented
+        FeatureListener.processFeatureExit(this, ctx);
     }
     }
 
 
     @Override
     @Override
     public void enterFeatureBody(GeneratedYangParser.FeatureBodyContext ctx) {
     public void enterFeatureBody(GeneratedYangParser.FeatureBodyContext ctx) {
-        //TODO : to be implemented
+        // do nothing
     }
     }
 
 
     @Override
     @Override
     public void exitFeatureBody(GeneratedYangParser.FeatureBodyContext ctx) {
     public void exitFeatureBody(GeneratedYangParser.FeatureBodyContext ctx) {
-        //TODO : to be implemented
+        // do nothing.
     }
     }
 
 
     @Override
     @Override
@@ -503,12 +507,12 @@ public class TreeWalkListener implements GeneratedYangListener {
 
 
     @Override
     @Override
     public void enterIfFeatureStatement(GeneratedYangParser.IfFeatureStatementContext ctx) {
     public void enterIfFeatureStatement(GeneratedYangParser.IfFeatureStatementContext ctx) {
-        // TODO: to be implemented
+        IfFeatureListener.processIfFeatureEntry(this, ctx);
     }
     }
 
 
     @Override
     @Override
     public void exitIfFeatureStatement(GeneratedYangParser.IfFeatureStatementContext ctx) {
     public void exitIfFeatureStatement(GeneratedYangParser.IfFeatureStatementContext ctx) {
-        // TODO: to be implemented
+        // do nothing.
     }
     }
 
 
     @Override
     @Override
@@ -813,12 +817,12 @@ public class TreeWalkListener implements GeneratedYangListener {
 
 
     @Override
     @Override
     public void enterMustStatement(GeneratedYangParser.MustStatementContext ctx) {
     public void enterMustStatement(GeneratedYangParser.MustStatementContext ctx) {
-        // TODO: to be implemented
+        MustListener.processMustEntry(this, ctx);
     }
     }
 
 
     @Override
     @Override
     public void exitMustStatement(GeneratedYangParser.MustStatementContext ctx) {
     public void exitMustStatement(GeneratedYangParser.MustStatementContext ctx) {
-        // TODO: to be implemented
+        MustListener.processMustExit(this, ctx);
     }
     }
 
 
     @Override
     @Override
@@ -1083,12 +1087,12 @@ public class TreeWalkListener implements GeneratedYangListener {
 
 
     @Override
     @Override
     public void enterWhenStatement(GeneratedYangParser.WhenStatementContext ctx) {
     public void enterWhenStatement(GeneratedYangParser.WhenStatementContext ctx) {
-        // TODO: to be implemented
+        WhenListener.processWhenEntry(this, ctx);
     }
     }
 
 
     @Override
     @Override
     public void exitWhenStatement(GeneratedYangParser.WhenStatementContext ctx) {
     public void exitWhenStatement(GeneratedYangParser.WhenStatementContext ctx) {
-        // TODO: to be implemented
+        WhenListener.processWhenExit(this, ctx);
     }
     }
 
 
     @Override
     @Override

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ *  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]
+ *                         "}")
+ *
+ *
+ *
+ * ANTLR grammar rule
+ * featureStatement : FEATURE_KEYWORD string (STMTEND | LEFT_CURLY_BRACE featureBody RIGHT_CURLY_BRACE);
+ */
+
+import org.onosproject.yangutils.datamodel.YangFeature;
+import org.onosproject.yangutils.datamodel.YangFeatureHolder;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.datamodel.utils.YangConstructType.FEATURE_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.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.ListenerUtil.getValidIdentifier;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/**
+ * Represents listener based call back function corresponding to the "feature"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class FeatureListener {
+
+    /**
+     * Creates a new feature listener.
+     */
+    private FeatureListener() {
+    }
+
+    /**
+     * Performs validation and updates the data model tree.It is called when parser receives
+     * an input matching the grammar rule (feature).
+     *
+     * @param listener listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processFeatureEntry(TreeWalkListener listener,
+                                           GeneratedYangParser.FeatureStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, FEATURE_DATA, ctx.string().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.string().getText(), FEATURE_DATA, ctx);
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        if (tmpNode instanceof YangFeatureHolder) {
+            YangFeatureHolder featureHolder = (YangFeatureHolder) tmpNode;
+
+            YangFeature feature = new YangFeature();
+            feature.setName(identifier);
+
+            featureHolder.addFeatureList(feature);
+            listener.getParsedDataStack().push(feature);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, FEATURE_DATA,
+                    ctx.string().getText(), ENTRY));
+        }
+    }
+
+    /**
+     * Perform validations and updates the data model tree.It is called when parser exits from
+     * grammar rule(feature).
+     *
+     * @param listener listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processFeatureExit(TreeWalkListener listener,
+                                          GeneratedYangParser.FeatureStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, FEATURE_DATA, ctx.string().getText(), EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangFeature) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, FEATURE_DATA,
+                    ctx.string().getText(), EXIT));
+        }
+    }
+}

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ *
+ * if-feature-stmt     = if-feature-keyword sep identifier-ref-arg-str
+ *                        optsep stmtend
+ *
+ * ANTLR grammar rule
+ * ifFeatureStatement : IF_FEATURE_KEYWORD string STMTEND;
+ */
+
+import org.onosproject.yangutils.datamodel.YangFeature;
+import org.onosproject.yangutils.datamodel.YangIfFeature;
+import org.onosproject.yangutils.datamodel.YangIfFeatureHolder;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNodeIdentifier;
+import org.onosproject.yangutils.datamodel.YangResolutionInfo;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
+import org.onosproject.yangutils.linker.impl.YangResolutionInfoImpl;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.datamodel.utils.DataModelUtils.addResolutionInfo;
+import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.UNRESOLVED;
+import static org.onosproject.yangutils.datamodel.utils.YangConstructType.IF_FEATURE_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructExtendedListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.UNHANDLED_PARSED_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidNodeIdentifier;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/**
+ * Represents listener based call back function corresponding to the "if-feature"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class IfFeatureListener {
+
+    /**
+     * Creates a new IfFeature listener.
+     */
+    private IfFeatureListener() {
+    }
+
+    /**
+     * Performs validation and updates the data model tree.It is called when parser receives
+     * an input matching the grammar rule (if-feature).
+     *
+     * @param listener listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processIfFeatureEntry(TreeWalkListener listener,
+                                             GeneratedYangParser.IfFeatureStatementContext ctx) {
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, IF_FEATURE_DATA, ctx.string().getText(), ENTRY);
+
+        // Validate if-feature argument string
+        YangNodeIdentifier nodeIdentifier = getValidNodeIdentifier(ctx.string().getText(),
+                IF_FEATURE_DATA, ctx);
+
+        YangIfFeature ifFeature = new YangIfFeature();
+        ifFeature.setName(nodeIdentifier);
+        ifFeature.setResolvableStatus(UNRESOLVED);
+        YangIfFeatureHolder ifFeatureHolder;
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        if (tmpNode instanceof YangIfFeatureHolder) {
+            ifFeatureHolder = (YangIfFeatureHolder) tmpNode;
+            ifFeatureHolder.addIfFeatureList(ifFeature);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, IF_FEATURE_DATA,
+                    ctx.string().getText(), ENTRY));
+        }
+
+        // Add resolution information to the list
+        Parsable parentNode;
+        if (tmpNode instanceof YangLeafList || tmpNode instanceof YangLeaf
+                || tmpNode instanceof YangFeature) {
+            Parsable leafData = listener.getParsedDataStack().pop();
+            parentNode = listener.getParsedDataStack().peek();
+            listener.getParsedDataStack().push(leafData);
+        } else {
+            parentNode = tmpNode;
+        }
+
+        // Verify parent node of leaf
+        if (!(parentNode instanceof YangNode)) {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, IF_FEATURE_DATA,
+                    ctx.string().getText(), EXIT));
+        }
+
+        int errorLine = ctx.getStart().getLine();
+        int errorPosition = ctx.getStart().getCharPositionInLine();
+        YangResolutionInfoImpl resolutionInfo = new YangResolutionInfoImpl<YangIfFeature>(ifFeature,
+                (YangNode) parentNode, errorLine,
+                errorPosition);
+        addToResolutionList(resolutionInfo, ctx);
+    }
+
+    /**
+     * Add to resolution list.
+     *
+     * @param resolutionInfo resolution information.
+     * @param ctx            context object of the grammar rule
+     */
+    private static void addToResolutionList(YangResolutionInfo<YangIfFeature> resolutionInfo,
+                                            GeneratedYangParser.IfFeatureStatementContext ctx) {
+
+        try {
+            addResolutionInfo(resolutionInfo);
+        } catch (DataModelException e) {
+            throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
+                    IF_FEATURE_DATA, ctx.string().getText(), EXIT, e.getMessage()));
+        }
+    }
+}

@@ -16,11 +16,13 @@
 
 
 package org.onosproject.yangutils.parser.impl.listeners;
 package org.onosproject.yangutils.parser.impl.listeners;
 
 
+import java.util.Date;
 import org.onosproject.yangutils.datamodel.ResolvableType;
 import org.onosproject.yangutils.datamodel.ResolvableType;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangReferenceResolver;
 import org.onosproject.yangutils.datamodel.YangReferenceResolver;
 import org.onosproject.yangutils.datamodel.YangRevision;
 import org.onosproject.yangutils.datamodel.YangRevision;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.linker.exceptions.LinkerException;
 import org.onosproject.yangutils.linker.exceptions.LinkerException;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
@@ -34,8 +36,8 @@ import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMes
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
 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_CURRENT_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getCurrentDateForRevision;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
-import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.setCurrentDateForRevision;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.translator.tojava.YangDataModelFactory.getYangModuleNode;
 import static org.onosproject.yangutils.translator.tojava.YangDataModelFactory.getYangModuleNode;
@@ -91,13 +93,6 @@ public final class ModuleListener {
             yangModule.setVersion((byte) 1);
             yangModule.setVersion((byte) 1);
         }
         }
 
 
-        if (ctx.moduleBody().revisionStatements().revisionStatement().isEmpty()) {
-            String currentDate = setCurrentDateForRevision();
-            YangRevision currentRevision = new YangRevision();
-            currentRevision.setRevDate(currentDate);
-            yangModule.setRevision(currentRevision);
-        }
-
         listener.getParsedDataStack().push(yangModule);
         listener.getParsedDataStack().push(yangModule);
     }
     }
 
 
@@ -113,12 +108,23 @@ public final class ModuleListener {
         // Check for stack to be non empty.
         // Check for stack to be non empty.
         checkStackIsNotEmpty(listener, MISSING_HOLDER, MODULE_DATA, ctx.identifier().getText(), EXIT);
         checkStackIsNotEmpty(listener, MISSING_HOLDER, MODULE_DATA, ctx.identifier().getText(), EXIT);
 
 
-        if (!(listener.getParsedDataStack().peek() instanceof YangModule)) {
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        if (!(tmpNode instanceof YangModule)) {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, MODULE_DATA,
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, MODULE_DATA,
                     ctx.identifier().getText(), EXIT));
                     ctx.identifier().getText(), EXIT));
         }
         }
+
+        if (((YangModule) tmpNode).getRevision() == null) {
+            Date currentDate = getCurrentDateForRevision();
+            YangRevision currentRevision = new YangRevision();
+            currentRevision.setRevDate(currentDate);
+            ((YangModule) tmpNode).setRevision(currentRevision);
+        }
+
         try {
         try {
             ((YangReferenceResolver) listener.getParsedDataStack()
             ((YangReferenceResolver) listener.getParsedDataStack()
+                    .peek()).resolveSelfFileLinking(ResolvableType.YANG_IF_FEATURE);
+            ((YangReferenceResolver) listener.getParsedDataStack()
                     .peek()).resolveSelfFileLinking(ResolvableType.YANG_USES);
                     .peek()).resolveSelfFileLinking(ResolvableType.YANG_USES);
             ((YangReferenceResolver) listener.getParsedDataStack()
             ((YangReferenceResolver) listener.getParsedDataStack()
                     .peek()).resolveSelfFileLinking(ResolvableType.YANG_DERIVED_DATA_TYPE);
                     .peek()).resolveSelfFileLinking(ResolvableType.YANG_DERIVED_DATA_TYPE);

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import org.onosproject.yangutils.datamodel.YangMust;
+import org.onosproject.yangutils.datamodel.YangMustHolder;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.datamodel.utils.YangConstructType.MUST_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.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.ListenerUtil.removeQuotesAndHandleConcat;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ *
+ *  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]
+ *                          "}")
+ *
+ * ANTLR grammar rule
+ * mustStatement : MUST_KEYWORD string (STMTEND | LEFT_CURLY_BRACE commonStatements RIGHT_CURLY_BRACE);
+ */
+
+/**
+ * Represents listener based call back function corresponding to the
+ * "must" rule defined in ANTLR grammar file for corresponding ABNF rule
+ * in RFC 6020.
+ */
+public final class MustListener {
+
+    /**
+     * Creates a new must listener.
+     */
+    private MustListener() {
+    }
+
+    /**
+     * Perform validations and updates the data model tree.It is called when parser
+     * receives an input matching the grammar rule (must).
+     *
+     * @param listener listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processMustEntry(TreeWalkListener listener,
+                                        GeneratedYangParser.MustStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, MUST_DATA, ctx.string().getText(), ENTRY);
+        String constraint = removeQuotesAndHandleConcat(ctx.string().getText());
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        if (tmpNode instanceof YangMustHolder) {
+
+            YangMust must = new YangMust();
+            must.setConstraint(constraint);
+
+            YangMustHolder mustHolder = (YangMustHolder) tmpNode;
+            mustHolder.addMust(must);
+
+            listener.getParsedDataStack().push(must);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, MUST_DATA,
+                    ctx.string().getText(), ENTRY));
+        }
+
+    }
+
+    /**
+     * Performs validation and updates the data model tree.It is called when parser
+     * exits from grammar rule (must).
+     *
+     * @param listener listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processMustExit(TreeWalkListener listener,
+                                       GeneratedYangParser.MustStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, MUST_DATA, ctx.string().getText(), EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangMust) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, MUST_DATA,
+                    ctx.string().getText(), EXIT));
+        }
+    }
+}

@@ -16,6 +16,7 @@
 
 
 package org.onosproject.yangutils.parser.impl.listeners;
 package org.onosproject.yangutils.parser.impl.listeners;
 
 
+import java.util.Date;
 import org.onosproject.yangutils.datamodel.YangImport;
 import org.onosproject.yangutils.datamodel.YangImport;
 import org.onosproject.yangutils.datamodel.YangInclude;
 import org.onosproject.yangutils.datamodel.YangInclude;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.datamodel.utils.Parsable;
@@ -28,8 +29,7 @@ import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLoc
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
 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.INVALID_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
-import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.isDateValid;
-import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.removeQuotesAndHandleConcat;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidDateFromString;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 
 
 /*
 /*
@@ -87,13 +87,7 @@ public final class RevisionDateListener {
         checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATE_DATA, ctx.dateArgumentString().getText(),
         checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATE_DATA, ctx.dateArgumentString().getText(),
                 ENTRY);
                 ENTRY);
 
 
-        String date = removeQuotesAndHandleConcat(ctx.dateArgumentString().getText());
-        if (!isDateValid(date)) {
-            ParserException parserException = new ParserException("YANG file error: Input date is not correct");
-            parserException.setLine(ctx.getStart().getLine());
-            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
-            throw parserException;
-        }
+        Date date = getValidDateFromString(ctx.dateArgumentString().getText(), ctx);
 
 
         // Obtain the node of the stack.
         // Obtain the node of the stack.
         Parsable tmpNode = listener.getParsedDataStack().peek();
         Parsable tmpNode = listener.getParsedDataStack().peek();

@@ -16,6 +16,7 @@
 
 
 package org.onosproject.yangutils.parser.impl.listeners;
 package org.onosproject.yangutils.parser.impl.listeners;
 
 
+import java.util.Date;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangRevision;
 import org.onosproject.yangutils.datamodel.YangRevision;
 import org.onosproject.yangutils.datamodel.YangSubModule;
 import org.onosproject.yangutils.datamodel.YangSubModule;
@@ -31,8 +32,7 @@ import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMes
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
 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_CURRENT_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
-import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.isDateValid;
-import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.removeQuotesAndHandleConcat;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidDateFromString;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 
 
 /*
 /*
@@ -88,20 +88,7 @@ public final class RevisionListener {
         // Check for stack to be non empty.
         // Check for stack to be non empty.
         checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATA, ctx.dateArgumentString().getText(), ENTRY);
         checkStackIsNotEmpty(listener, MISSING_HOLDER, REVISION_DATA, ctx.dateArgumentString().getText(), ENTRY);
 
 
-        // Validate for reverse chronological order of revision & for revision
-        // value.
-        if (!validateRevision(listener, ctx)) {
-            return;
-            // TODO to be implemented.
-        }
-
-        String date = removeQuotesAndHandleConcat(ctx.dateArgumentString().getText());
-        if (!isDateValid(date)) {
-            ParserException parserException = new ParserException("YANG file error: Input date is not correct");
-            parserException.setLine(ctx.getStart().getLine());
-            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
-            throw parserException;
-        }
+        Date date = getValidDateFromString(ctx.dateArgumentString().getText(), ctx);
 
 
         YangRevision revisionNode = new YangRevision();
         YangRevision revisionNode = new YangRevision();
         revisionNode.setRevDate(date);
         revisionNode.setRevDate(date);
@@ -134,12 +121,26 @@ public final class RevisionListener {
             switch (tmpNode.getYangConstructType()) {
             switch (tmpNode.getYangConstructType()) {
                 case MODULE_DATA: {
                 case MODULE_DATA: {
                     YangModule module = (YangModule) tmpNode;
                     YangModule module = (YangModule) tmpNode;
-                    module.setRevision((YangRevision) tmpRevisionNode);
+                    if (module.getRevision() != null) {
+                        Date curRevisionDate = module.getRevision().getRevDate();
+                        if (curRevisionDate.before(((YangRevision) tmpRevisionNode).getRevDate())) {
+                            module.setRevision((YangRevision) tmpRevisionNode);
+                        }
+                    } else {
+                        module.setRevision((YangRevision) tmpRevisionNode);
+                    }
                     break;
                     break;
                 }
                 }
                 case SUB_MODULE_DATA: {
                 case SUB_MODULE_DATA: {
                     YangSubModule subModule = (YangSubModule) tmpNode;
                     YangSubModule subModule = (YangSubModule) tmpNode;
-                    subModule.setRevision((YangRevision) tmpRevisionNode);
+                    if (subModule.getRevision() != null) {
+                        Date curRevisionDate = subModule.getRevision().getRevDate();
+                        if (curRevisionDate.before(((YangRevision) tmpRevisionNode).getRevDate())) {
+                            subModule.setRevision((YangRevision) tmpRevisionNode);
+                        }
+                    } else {
+                        subModule.setRevision((YangRevision) tmpRevisionNode);
+                    }
                     break;
                     break;
                 }
                 }
                 default:
                 default:

@@ -16,11 +16,13 @@
 
 
 package org.onosproject.yangutils.parser.impl.listeners;
 package org.onosproject.yangutils.parser.impl.listeners;
 
 
+import java.util.Date;
 import org.onosproject.yangutils.datamodel.ResolvableType;
 import org.onosproject.yangutils.datamodel.ResolvableType;
 import org.onosproject.yangutils.datamodel.YangReferenceResolver;
 import org.onosproject.yangutils.datamodel.YangReferenceResolver;
 import org.onosproject.yangutils.datamodel.YangRevision;
 import org.onosproject.yangutils.datamodel.YangRevision;
 import org.onosproject.yangutils.datamodel.YangSubModule;
 import org.onosproject.yangutils.datamodel.YangSubModule;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
 import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
 import org.onosproject.yangutils.linker.exceptions.LinkerException;
 import org.onosproject.yangutils.linker.exceptions.LinkerException;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
@@ -34,8 +36,8 @@ import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMes
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
 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_CURRENT_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getCurrentDateForRevision;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.getValidIdentifier;
-import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.setCurrentDateForRevision;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 import static org.onosproject.yangutils.translator.tojava.YangDataModelFactory.getYangSubModuleNode;
 import static org.onosproject.yangutils.translator.tojava.YangDataModelFactory.getYangSubModuleNode;
@@ -94,13 +96,6 @@ public final class SubModuleListener {
             yangSubModule.setVersion((byte) 1);
             yangSubModule.setVersion((byte) 1);
         }
         }
 
 
-        if (ctx.submoduleBody().revisionStatements().revisionStatement().isEmpty()) {
-            String currentDate = setCurrentDateForRevision();
-            YangRevision currentRevision = new YangRevision();
-            currentRevision.setRevDate(currentDate);
-            yangSubModule.setRevision(currentRevision);
-        }
-
         listener.getParsedDataStack().push(yangSubModule);
         listener.getParsedDataStack().push(yangSubModule);
     }
     }
 
 
@@ -118,12 +113,23 @@ public final class SubModuleListener {
         checkStackIsNotEmpty(listener, MISSING_HOLDER, SUB_MODULE_DATA, ctx.identifier().getText(),
         checkStackIsNotEmpty(listener, MISSING_HOLDER, SUB_MODULE_DATA, ctx.identifier().getText(),
                 EXIT);
                 EXIT);
 
 
-        if (!(listener.getParsedDataStack().peek() instanceof YangSubModule)) {
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        if (!(tmpNode instanceof YangSubModule)) {
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, SUB_MODULE_DATA,
             throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, SUB_MODULE_DATA,
                     ctx.identifier().getText(), EXIT));
                     ctx.identifier().getText(), EXIT));
         }
         }
+
+        if (((YangSubModule) tmpNode).getRevision() == null) {
+            Date currentDate = getCurrentDateForRevision();
+            YangRevision currentRevision = new YangRevision();
+            currentRevision.setRevDate(currentDate);
+            ((YangSubModule) tmpNode).setRevision(currentRevision);
+        }
+
         try {
         try {
             ((YangReferenceResolver) listener.getParsedDataStack().peek())
             ((YangReferenceResolver) listener.getParsedDataStack().peek())
+                    .resolveSelfFileLinking(ResolvableType.YANG_IF_FEATURE);
+            ((YangReferenceResolver) listener.getParsedDataStack().peek())
                     .resolveSelfFileLinking(ResolvableType.YANG_USES);
                     .resolveSelfFileLinking(ResolvableType.YANG_USES);
             ((YangReferenceResolver) listener.getParsedDataStack().peek())
             ((YangReferenceResolver) listener.getParsedDataStack().peek())
                     .resolveSelfFileLinking(ResolvableType.YANG_DERIVED_DATA_TYPE);
                     .resolveSelfFileLinking(ResolvableType.YANG_DERIVED_DATA_TYPE);

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import org.onosproject.yangutils.datamodel.YangWhen;
+import org.onosproject.yangutils.datamodel.YangWhenHolder;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+import static org.onosproject.yangutils.datamodel.utils.YangConstructType.WHEN_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.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.ListenerUtil.removeQuotesAndHandleConcat;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ *
+ *  when-stmt           = when-keyword sep string optsep
+ *                        (";" /
+ *                         "{" stmtsep
+ *                             ;; these stmts can appear in any order
+ *                             [description-stmt stmtsep]
+ *                             [reference-stmt stmtsep]
+ *                          "}")
+ *
+ * ANTLR grammar rule
+ * whenStatement : WHEN_KEYWORD string (STMTEND | LEFT_CURLY_BRACE ((descriptionStatement? referenceStatement?)
+ *       | (referenceStatement? descriptionStatement?)) RIGHT_CURLY_BRACE);
+ */
+
+/**
+ * Represents listener based call back function corresponding to the
+ * "when" rule defined in ANTLR grammar file for corresponding ABNF rule
+ * in RFC 6020.
+ */
+public final class WhenListener {
+
+    /**
+     * Creates a new when listener.
+     */
+    private WhenListener() {
+    }
+
+    /**
+     * Perform validations and updates the data model tree.It is called when parser
+     * receives an input matching the grammar rule (when).
+     *
+     * @param listener listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processWhenEntry(TreeWalkListener listener,
+                                        GeneratedYangParser.WhenStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, WHEN_DATA, ctx.string().getText(), ENTRY);
+        String condition = removeQuotesAndHandleConcat(ctx.string().getText());
+
+        YangWhenHolder whenHolder;
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        if (tmpNode instanceof YangWhenHolder) {
+            whenHolder = (YangWhenHolder) tmpNode;
+
+            YangWhen when = new YangWhen();
+            when.setCondition(condition);
+
+            whenHolder.setWhen(when);
+            listener.getParsedDataStack().push(when);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER,
+                    WHEN_DATA, ctx.string().getText(), ENTRY));
+        }
+    }
+
+    /**
+     * Performs validation and updates the data model tree.It is called when parser
+     * exits from grammar rule (when).
+     *
+     * @param listener listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processWhenExit(TreeWalkListener listener,
+                                       GeneratedYangParser.WhenStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, WHEN_DATA, ctx.string().getText(), EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangWhen) {
+            listener.getParsedDataStack().pop();
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, WHEN_DATA,
+                    ctx.string().getText(), EXIT));
+        }
+    }
+}

@@ -18,7 +18,7 @@ package org.onosproject.yangutils.parser.impl.parserutils;
 
 
 import java.text.ParseException;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.text.SimpleDateFormat;
-import java.util.Calendar;
+import java.util.Date;
 import java.util.LinkedList;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.List;
 import java.util.regex.Pattern;
 import java.util.regex.Pattern;
@@ -30,20 +30,18 @@ import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 
 
 import static org.onosproject.yangutils.utils.UtilConstants.ADD;
 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.CARET;
+import static org.onosproject.yangutils.utils.UtilConstants.COLON;
 import static org.onosproject.yangutils.utils.UtilConstants.CURRENTLY_UNSUPPORTED;
 import static org.onosproject.yangutils.utils.UtilConstants.CURRENTLY_UNSUPPORTED;
-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.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.FALSE;
-import static org.onosproject.yangutils.utils.UtilConstants.YANG_FILE_ERROR;
 import static org.onosproject.yangutils.utils.UtilConstants.IDENTITYREF;
 import static org.onosproject.yangutils.utils.UtilConstants.IDENTITYREF;
-import static org.onosproject.yangutils.utils.UtilConstants.LEAFREF;
 import static org.onosproject.yangutils.utils.UtilConstants.INSTANCE_IDENTIFIER;
 import static org.onosproject.yangutils.utils.UtilConstants.INSTANCE_IDENTIFIER;
+import static org.onosproject.yangutils.utils.UtilConstants.LEAFREF;
+import static org.onosproject.yangutils.utils.UtilConstants.QUOTES;
+import static org.onosproject.yangutils.utils.UtilConstants.SLASH;
+import static org.onosproject.yangutils.utils.UtilConstants.TRUE;
+import static org.onosproject.yangutils.utils.UtilConstants.YANG_FILE_ERROR;
 
 
 /**
 /**
  * Represents an utility for listener.
  * Represents an utility for listener.
@@ -256,17 +254,24 @@ public final class ListenerUtil {
     }
     }
 
 
     /**
     /**
-     * Sets current date and makes it in usable format for revision.
+     * Returns current date and makes it in usable format for revision.
      *
      *
      * @return usable current date format for revision
      * @return usable current date format for revision
      */
      */
-    public static String setCurrentDateForRevision() {
+    public static Date getCurrentDateForRevision() {
 
 
-        Calendar date = Calendar.getInstance();
         SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
         SimpleDateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
-        String dateForRevision = dateFormat.format(date.getTime()).replaceAll(SLASH, HYPHEN).replaceAll(SPACE,
-                EMPTY_STRING);
-        return dateForRevision;
+
+        Date date = new Date();
+        String dateInString = dateFormat.format(date);
+        try {
+            //if not valid, it will throw ParseException
+            Date now = dateFormat.parse(dateInString);
+            return date;
+        } catch (ParseException e) {
+            ParserException parserException = new ParserException("YANG file error: Input date is not correct");
+            throw parserException;
+        }
     }
     }
 
 
     /**
     /**
@@ -373,4 +378,35 @@ public final class ListenerUtil {
         parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
         parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
         throw parserException;
         throw parserException;
     }
     }
+
+    /**
+     * Returns date and makes it in usable format for revision.
+     *
+     * @param dateInString date argument string from yang file
+     * @param ctx          yang construct's context to get the line number and character position
+     * @return date format for revision
+     */
+    public static Date getValidDateFromString(String dateInString, ParserRuleContext ctx) {
+        String dateArgument = removeQuotesAndHandleConcat(dateInString);
+        if (dateArgument == null || !dateArgument.matches(DATE_PATTERN)) {
+            ParserException parserException = new ParserException("YANG file error: Input date is not correct");
+            parserException.setLine(ctx.getStart().getLine());
+            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+            throw parserException;
+        }
+
+        SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT);
+        sdf.setLenient(false);
+
+        try {
+            //if not valid, it will throw ParseException
+            Date date = sdf.parse(dateArgument);
+            return date;
+        } catch (ParseException e) {
+            ParserException parserException = new ParserException("YANG file error: Input date is not correct");
+            parserException.setLine(ctx.getStart().getLine());
+            parserException.setCharPosition(ctx.getStart().getCharPositionInLine());
+            throw parserException;
+        }
+    }
 }
 }
\ No newline at end of file

@@ -18,7 +18,9 @@ package org.onosproject.yangutils.translator.tojava.utils;
 
 
 import java.io.File;
 import java.io.File;
 import java.io.IOException;
 import java.io.IOException;
+import java.text.SimpleDateFormat;
 import java.util.ArrayList;
 import java.util.ArrayList;
+import java.util.Date;
 import java.util.List;
 import java.util.List;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.translator.exception.TranslatorException;
 import org.onosproject.yangutils.translator.exception.TranslatorException;
@@ -59,6 +61,7 @@ public final class JavaIdentifierSyntax {
     private static final int INDEX_TWO = 2;
     private static final int INDEX_TWO = 2;
     private static final int VALUE_CHECK = 10;
     private static final int VALUE_CHECK = 10;
     private static final String ZERO = "0";
     private static final String ZERO = "0";
+    private static final String DATE_FORMAT = "yyyy-MM-dd";
 
 
     /**
     /**
      * Create instance of java identifier syntax.
      * Create instance of java identifier syntax.
@@ -75,7 +78,7 @@ public final class JavaIdentifierSyntax {
      * @param conflictResolver object of YANG to java naming conflict util
      * @param conflictResolver object of YANG to java naming conflict util
      * @return the root package string
      * @return the root package string
      */
      */
-    public static String getRootPackage(byte version, String nameSpace, String revision,
+    public static String getRootPackage(byte version, String nameSpace, Date revision,
                                         YangToJavaNamingConflictUtil conflictResolver) {
                                         YangToJavaNamingConflictUtil conflictResolver) {
 
 
         String pkg;
         String pkg;
@@ -125,30 +128,23 @@ public final class JavaIdentifierSyntax {
      *
      *
      * @param date YANG module revision
      * @param date YANG module revision
      * @return revision string
      * @return revision string
-     * @throws TranslatorException when date is invalid.
      */
      */
-    private static String getYangRevisionStr(String date) throws TranslatorException {
-
-        String[] revisionArr = date.split(HYPHEN);
+    private static String getYangRevisionStr(Date date) {
+        SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT);
+        String dateInString = sdf.format(date);
+        String[] revisionArr = dateInString.split(HYPHEN);
 
 
         String rev = REVISION_PREFIX;
         String rev = REVISION_PREFIX;
         rev = rev + revisionArr[INDEX_ZERO];
         rev = rev + revisionArr[INDEX_ZERO];
 
 
-        if (Integer.parseInt(revisionArr[INDEX_ONE]) <= MAX_MONTHS
-                && Integer.parseInt(revisionArr[INDEX_TWO]) <= MAX_DAYS) {
-            for (int i = INDEX_ONE; i < revisionArr.length; i++) {
-
-                Integer val = Integer.parseInt(revisionArr[i]);
-                if (val < VALUE_CHECK) {
-                    rev = rev + ZERO;
-                }
-                rev = rev + val;
+        for (int i = INDEX_ONE; i < revisionArr.length; i++) {
+            Integer val = Integer.parseInt(revisionArr[i]);
+            if (val < VALUE_CHECK) {
+                rev = rev + ZERO;
             }
             }
-
-            return rev;
-        } else {
-            throw new TranslatorException("Date in revision is not proper: " + date);
+            rev = rev + val;
         }
         }
+        return rev;
     }
     }
 
 
     /**
     /**

@@ -1140,6 +1140,12 @@ public final class UtilConstants {
             + "grouping for given uses";
             + "grouping for given uses";
 
 
     /**
     /**
+     * Static attribute for grouping linker error information.
+     */
+    public static final String FEATURE_LINKER_ERROR = "YANG file error: Unable to find feature "
+            + "for given if-feature";
+
+    /**
      * Static attribute for reference.
      * Static attribute for reference.
      */
      */
     public static final String REFERENCE = "Reference";
     public static final String REFERENCE = "Reference";

@@ -16,14 +16,15 @@
 
 
 package org.onosproject.yangutils.parser.impl.listeners;
 package org.onosproject.yangutils.parser.impl.listeners;
 
 
+import java.io.IOException;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
 import org.junit.Test;
 import org.junit.Test;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
 import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
 
 
-import java.io.IOException;
-
 import static org.hamcrest.core.Is.is;
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertThat;
 
 
@@ -33,6 +34,8 @@ import static org.junit.Assert.assertThat;
 public class ImportListenerTest {
 public class ImportListenerTest {
 
 
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
+    private static final String DATE_FORMAT = "yyyy-MM-dd";
+    private final SimpleDateFormat simpleDateFormat = new SimpleDateFormat(DATE_FORMAT);
 
 
     /**
     /**
      * Checks if mandatory parameter prefix is present in import.
      * Checks if mandatory parameter prefix is present in import.
@@ -65,12 +68,12 @@ public class ImportListenerTest {
      * Checks if import listener updates the data model tree.
      * Checks if import listener updates the data model tree.
      */
      */
     @Test
     @Test
-    public void processImportValidEntry() throws IOException, ParserException {
+    public void processImportValidEntry() throws IOException, ParserException, ParseException {
 
 
         YangNode node = manager.getDataModel("src/test/resources/ImportValidEntry.yang");
         YangNode node = manager.getDataModel("src/test/resources/ImportValidEntry.yang");
 
 
         // Checks for the revision value in data model tree.
         // Checks for the revision value in data model tree.
-        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is("2015-02-03"));
+        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is(simpleDateFormat.parse("2015-02-03")));
         // Checks for the prefix id in data model tree.
         // Checks for the prefix id in data model tree.
         assertThat(((YangModule) node).getImportList().get(0).getPrefixId(), is("On2"));
         assertThat(((YangModule) node).getImportList().get(0).getPrefixId(), is("On2"));
         // Checks for the module name in data model tree.
         // Checks for the module name in data model tree.

@@ -16,14 +16,15 @@
 
 
 package org.onosproject.yangutils.parser.impl.listeners;
 package org.onosproject.yangutils.parser.impl.listeners;
 
 
+import java.io.IOException;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
 import org.junit.Test;
 import org.junit.Test;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
 import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
 
 
-import java.io.IOException;
-
 import static org.hamcrest.core.Is.is;
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertThat;
 
 
@@ -33,6 +34,8 @@ import static org.junit.Assert.assertThat;
 public class IncludeListenerTest {
 public class IncludeListenerTest {
 
 
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
+    private static final String DATE_FORMAT = "yyyy-MM-dd";
+    private final SimpleDateFormat simpleDateFormat = new SimpleDateFormat(DATE_FORMAT);
 
 
     /**
     /**
      * Checks if include listener with ; is valid and updates the data
      * Checks if include listener with ; is valid and updates the data
@@ -65,43 +68,43 @@ public class IncludeListenerTest {
      * and updates the data model tree.
      * and updates the data model tree.
      */
      */
     @Test
     @Test
-    public void processIncludeWithDate() throws IOException, ParserException {
+    public void processIncludeWithDate() throws IOException, ParserException, ParseException {
 
 
         YangNode node = manager.getDataModel("src/test/resources/IncludeWithDate.yang");
         YangNode node = manager.getDataModel("src/test/resources/IncludeWithDate.yang");
 
 
         // Checks for the sub module name in data model tree.
         // Checks for the sub module name in data model tree.
         assertThat(((YangModule) node).getIncludeList().get(0).getSubModuleName(), is("itut"));
         assertThat(((YangModule) node).getIncludeList().get(0).getSubModuleName(), is("itut"));
-        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is("2016-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is(simpleDateFormat.parse("2016-02-03")));
     }
     }
 
 
     /**
     /**
      * Checks if include has more than one occurrence.
      * Checks if include has more than one occurrence.
      */
      */
     @Test
     @Test
-    public void processIncludeMultiInstance() throws IOException, ParserException {
+    public void processIncludeMultiInstance() throws IOException, ParserException, ParseException {
 
 
         YangNode node = manager.getDataModel("src/test/resources/IncludeMultiInstance.yang");
         YangNode node = manager.getDataModel("src/test/resources/IncludeMultiInstance.yang");
 
 
         // Checks for the sub module name in data model tree.
         // Checks for the sub module name in data model tree.
         assertThat(((YangModule) node).getIncludeList().get(0).getSubModuleName(), is("itut"));
         assertThat(((YangModule) node).getIncludeList().get(0).getSubModuleName(), is("itut"));
-        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is("2016-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is(simpleDateFormat.parse("2016-02-03")));
         assertThat(((YangModule) node).getIncludeList().get(1).getSubModuleName(), is("sdn"));
         assertThat(((YangModule) node).getIncludeList().get(1).getSubModuleName(), is("sdn"));
-        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is("2014-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is(simpleDateFormat.parse("2014-02-03")));
     }
     }
 
 
     /**
     /**
      * Checks if include and import can come in any order.
      * Checks if include and import can come in any order.
      */
      */
     @Test
     @Test
-    public void processIncludeImportAnyOrder() throws IOException, ParserException {
+    public void processIncludeImportAnyOrder() throws IOException, ParserException, ParseException {
 
 
         YangNode node = manager.getDataModel("src/test/resources/IncludeImportAnyOrder.yang");
         YangNode node = manager.getDataModel("src/test/resources/IncludeImportAnyOrder.yang");
 
 
         // Checks for the sub module name in data model tree.
         // Checks for the sub module name in data model tree.
         assertThat(((YangModule) node).getIncludeList().get(0).getSubModuleName(), is("itut"));
         assertThat(((YangModule) node).getIncludeList().get(0).getSubModuleName(), is("itut"));
-        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is("2016-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is(simpleDateFormat.parse("2016-02-03")));
         assertThat(((YangModule) node).getIncludeList().get(1).getSubModuleName(), is("sdn"));
         assertThat(((YangModule) node).getIncludeList().get(1).getSubModuleName(), is("sdn"));
-        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is("2014-02-03"));
+        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is(simpleDateFormat.parse("2014-02-03")));
     }
     }
 
 
     /**
     /**

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangMust;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.ListIterator;
+
+import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Test cases for testing must listener functionality.
+ */
+public class MustListenerTest {
+
+    private final YangUtilsParserManager manager = new YangUtilsParserManager();
+
+    /**
+     * Checks if must listener updates the data model.
+     */
+    @Test
+    public void processContainerSubStatementMust() throws IOException, ParserException {
+        YangNode node = manager.getDataModel("src/test/resources/ContainerSubStatementMust.yang");
+
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangContainer yangContainer = (YangContainer) yangNode.getChild();
+        assertThat(yangContainer.getName(), is("interface"));
+
+        String expectedConstraint = "ifType != 'ethernet' or (ifType = 'ethernet' and ifMTU = 1500)";
+        List<YangMust> mustConstraintList = yangContainer.getListOfMust();
+        assertThat(mustConstraintList.iterator().next().getConstraint(), is(expectedConstraint));
+    }
+
+    /**
+     * Checks if must listener updates the data model.
+     */
+    @Test
+    public void processLeafSubStatementMust() throws IOException, ParserException {
+        YangNode node = manager.getDataModel("src/test/resources/LeafSubStatementMust.yang");
+
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        ListIterator<YangLeaf> leafIterator = yangNode.getListOfLeaf().listIterator();
+        YangLeaf leafInfo = leafIterator.next();
+
+        assertThat(leafInfo.getListOfMust().iterator().next().getConstraint(), is("ifType != 'ethernet'"));
+    }
+}
\ No newline at end of file

@@ -16,14 +16,15 @@
 
 
 package org.onosproject.yangutils.parser.impl.listeners;
 package org.onosproject.yangutils.parser.impl.listeners;
 
 
+import java.io.IOException;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
 import org.junit.Test;
 import org.junit.Test;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
 import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
 
 
-import java.io.IOException;
-
 import static org.hamcrest.core.Is.is;
 import static org.hamcrest.core.Is.is;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertThat;
 
 
@@ -33,6 +34,8 @@ import static org.junit.Assert.assertThat;
 public class RevisionDateListenerTest {
 public class RevisionDateListenerTest {
 
 
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
+    private static final String DATE_FORMAT = "yyyy-MM-dd";
+    private final SimpleDateFormat simpleDateFormat = new SimpleDateFormat(DATE_FORMAT);
 
 
     /**
     /**
      * Checks if revision date syntax is correct in include.
      * Checks if revision date syntax is correct in include.
@@ -56,26 +59,26 @@ public class RevisionDateListenerTest {
      * Checks revision date in quotes inside include.
      * Checks revision date in quotes inside include.
      */
      */
     @Test
     @Test
-    public void processRevisionDateInQuotesAtInclude() throws IOException, ParserException {
+    public void processRevisionDateInQuotesAtInclude() throws IOException, ParserException, ParseException {
 
 
         YangNode node = manager.getDataModel("src/test/resources/RevisionDateInQuotesAtInclude.yang");
         YangNode node = manager.getDataModel("src/test/resources/RevisionDateInQuotesAtInclude.yang");
         // Checks for the version value in data model tree.
         // Checks for the version value in data model tree.
-        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is("2015-02-03"));
-        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is("2016-02-03"));
-        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is("2014-02-03"));
+        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is(simpleDateFormat.parse("2015-02-03")));
+        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is(simpleDateFormat.parse("2016-02-03")));
+        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is(simpleDateFormat.parse("2014-02-03")));
     }
     }
 
 
     /**
     /**
      * Checks revision date in quotes inside import.
      * Checks revision date in quotes inside import.
      */
      */
     @Test
     @Test
-    public void processRevisionDateInQuotesAtImport() throws IOException, ParserException {
+    public void processRevisionDateInQuotesAtImport() throws IOException, ParserException, ParseException {
 
 
         YangNode node = manager.getDataModel("src/test/resources/RevisionDateInQuotesAtImport.yang");
         YangNode node = manager.getDataModel("src/test/resources/RevisionDateInQuotesAtImport.yang");
         // Checks for the version value in data model tree.
         // Checks for the version value in data model tree.
-        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is("2015-02-03"));
-        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is("2016-02-03"));
-        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is("2014-02-03"));
+        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is(simpleDateFormat.parse("2015-02-03")));
+        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is(simpleDateFormat.parse("2016-02-03")));
+        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is(simpleDateFormat.parse("2014-02-03")));
     }
     }
 
 
     /**
     /**
@@ -100,13 +103,13 @@ public class RevisionDateListenerTest {
      * Checks if revision date listener updates the data model tree.
      * Checks if revision date listener updates the data model tree.
      */
      */
     @Test
     @Test
-    public void processRevisionDateValidEntry() throws IOException, ParserException {
+    public void processRevisionDateValidEntry() throws IOException, ParserException, ParseException {
 
 
         YangNode node = manager.getDataModel("src/test/resources/RevisionDateValidEntry.yang");
         YangNode node = manager.getDataModel("src/test/resources/RevisionDateValidEntry.yang");
 
 
         // Checks for the version value in data model tree.
         // Checks for the version value in data model tree.
-        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is("2015-02-03"));
-        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is("2016-02-03"));
-        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is("2014-02-03"));
+        assertThat(((YangModule) node).getImportList().get(0).getRevision(), is(simpleDateFormat.parse("2015-02-03")));
+        assertThat(((YangModule) node).getIncludeList().get(0).getRevision(), is(simpleDateFormat.parse("2016-02-03")));
+        assertThat(((YangModule) node).getIncludeList().get(1).getRevision(), is(simpleDateFormat.parse("2014-02-03")));
     }
     }
 }
 }
\ No newline at end of file

@@ -16,14 +16,15 @@
 
 
 package org.onosproject.yangutils.parser.impl.listeners;
 package org.onosproject.yangutils.parser.impl.listeners;
 
 
+import java.io.IOException;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
 import org.junit.Test;
 import org.junit.Test;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangModule;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.datamodel.YangNode;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
 import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
 
 
-import java.io.IOException;
-
 import static org.hamcrest.core.Is.is;
 import static org.hamcrest.core.Is.is;
 import static org.hamcrest.core.IsNull.notNullValue;
 import static org.hamcrest.core.IsNull.notNullValue;
 import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertThat;
@@ -34,18 +35,19 @@ import static org.junit.Assert.assertThat;
 public class RevisionListenerTest {
 public class RevisionListenerTest {
 
 
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
     private final YangUtilsParserManager manager = new YangUtilsParserManager();
+    private static final String DATE_FORMAT = "yyyy-MM-dd";
+    private final SimpleDateFormat simpleDateFormat = new SimpleDateFormat(DATE_FORMAT);
 
 
     /**
     /**
      * Checks if revision doesn't have optional parameters "revision and
      * Checks if revision doesn't have optional parameters "revision and
      * description".
      * description".
      */
      */
     @Test
     @Test
-    public void processRevisionNoOptionalParameter() throws IOException, ParserException {
+    public void processRevisionNoOptionalParameter() throws IOException, ParserException, ParseException {
 
 
         YangNode node = manager.getDataModel("src/test/resources/RevisionNoOptionalParameter.yang");
         YangNode node = manager.getDataModel("src/test/resources/RevisionNoOptionalParameter.yang");
-
         // Checks for the version value in data model tree.
         // Checks for the version value in data model tree.
-        assertThat(((YangModule) node).getRevision().getRevDate(), is("2016-02-03"));
+        assertThat(((YangModule) node).getRevision().getRevDate(), is(simpleDateFormat.parse("2016-02-03")));
     }
     }
 
 
     /**
     /**
@@ -75,4 +77,14 @@ public class RevisionListenerTest {
         YangNode node = manager.getDataModel("src/test/resources/RevisionAbsence.yang");
         YangNode node = manager.getDataModel("src/test/resources/RevisionAbsence.yang");
         assertThat(((YangModule) node).getRevision().getRevDate(), notNullValue());
         assertThat(((YangModule) node).getRevision().getRevDate(), notNullValue());
     }
     }
+
+    /**
+     * Checks latest date is stored when there are multiple revisions.
+     */
+    @Test
+    public void processWithMultipleRevision() throws IOException, ParserException, ParseException {
+
+        YangNode node = manager.getDataModel("src/test/resources/MultipleRevision.yang");
+        assertThat(((YangModule) node).getRevision().getRevDate(), is(simpleDateFormat.parse("2013-07-15")));
+    }
 }
 }
\ No newline at end of file

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+
+import java.io.IOException;
+import java.util.ListIterator;
+
+import static org.hamcrest.core.Is.is;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Test cases for testing when listener functionality.
+ */
+public class WhenListenerTest {
+
+    private final YangUtilsParserManager manager = new YangUtilsParserManager();
+
+    /**
+     * Checks if when listener updates the data model.
+     */
+    @Test
+    public void processContainerSubStatementWhen() throws IOException, ParserException {
+        YangNode node = manager.getDataModel("src/test/resources/ContainerSubStatementWhen.yang");
+
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        YangList yangList = (YangList) yangNode.getChild();
+        assertThat(yangList.getName(), is("interface-switching-capability"));
+
+        YangContainer container = (YangContainer) yangList.getNextSibling();
+        assertThat(container.getName(), is("time-division-multiplex-capable"));
+
+        String expectedConstraint = "../switching-capability = 'TDM'";
+        assertThat(container.getWhen().getCondition(), is(expectedConstraint));
+    }
+
+    /**
+     * Checks if when listener updates the data model.
+     */
+    @Test
+    public void processLeafSubStatementWhen() throws IOException, ParserException {
+        YangNode node = manager.getDataModel("src/test/resources/LeafSubStatementWhen.yang");
+
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("Test"));
+
+        ListIterator<YangLeaf> leafIterator = yangNode.getListOfLeaf().listIterator();
+        YangLeaf leafInfo = leafIterator.next();
+
+        assertThat(leafInfo.getWhen().getCondition(), is("ifType != 'ethernet'"));
+    }
+}
\ No newline at end of file

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.plugin.manager;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.ListIterator;
+import org.apache.maven.plugin.MojoExecutionException;
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangFeature;
+import org.onosproject.yangutils.datamodel.YangIfFeature;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.linker.impl.YangLinkerManager;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.utils.io.impl.YangFileScanner;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+import static org.onosproject.yangutils.datamodel.YangNodeType.MODULE_NODE;
+import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.INTRA_FILE_RESOLVED;
+import static org.onosproject.yangutils.datamodel.utils.ResolvableStatus.RESOLVED;
+
+/**
+ * Test cases for testing inter file linking.
+ */
+public class InterFileIfFeatureLinkingTest {
+
+    private final YangUtilManager utilManager = new YangUtilManager();
+    private final YangLinkerManager yangLinkerManager = new YangLinkerManager();
+
+    /**
+     * Checks inter file feature linking with imported file.
+     */
+    @Test
+    public void processFeatureInImportedFile()
+            throws IOException, ParserException, MojoExecutionException {
+
+        String searchDir = "src/test/resources/interfilefeatureimport";
+        utilManager.createYangFileInfoSet(YangFileScanner.getYangFiles(searchDir));
+        utilManager.parseYangFileInfoSet();
+        utilManager.createYangNodeSet();
+
+        YangNode selfNode = null;
+        YangNode refNode1 = null;
+        YangNode refNode2 = null;
+
+        // Create YANG node set
+        yangLinkerManager.createYangNodeSet(utilManager.getYangNodeSet());
+
+        // Add references to import list.
+        yangLinkerManager.addRefToYangFilesImportList(utilManager.getYangNodeSet());
+
+        // Carry out inter-file linking.
+        yangLinkerManager.processInterFileLinking(utilManager.getYangNodeSet());
+
+        for (YangNode rootNode : utilManager.getYangNodeSet()) {
+            if (rootNode.getName().equals("syslog1")) {
+                selfNode = rootNode;
+            } else if (rootNode.getName().equals("syslog2")) {
+                refNode1 = rootNode;
+            } else {
+                refNode2 = rootNode;
+            }
+        }
+        // Check whether the data model tree returned is of type module.
+        assertThat(selfNode instanceof YangModule, is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(selfNode.getNodeType(), is(MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) selfNode;
+        assertThat(yangNode.getName(), is("syslog1"));
+
+        ListIterator<YangFeature> featureIterator = yangNode.getFeatureList().listIterator();
+        YangFeature feature = featureIterator.next();
+        assertThat(feature.getName(), is("frr-te"));
+
+        YangIfFeature ifFeature = feature.getIfFeatureList().iterator().next();
+        assertThat(ifFeature.getName().getName(), is("p2mp-te"));
+        assertThat(ifFeature.getName().getPrefix(), is("sys2"));
+        assertThat(ifFeature.getResolvableStatus(), is(RESOLVED));
+
+        YangContainer container = (YangContainer) selfNode.getChild();
+        assertThat(container.getName(), is("speed"));
+        YangLeaf leaf = container.getListOfLeaf().iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("frr-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(RESOLVED));
+    }
+
+    /**
+     * Checks inter file feature linking with included file.
+     */
+    @Test
+    public void processFeatureInIncludedFile()
+            throws IOException, ParserException, MojoExecutionException {
+
+        String searchDir = "src/test/resources/interfilefeatureinclude";
+        utilManager.createYangFileInfoSet(YangFileScanner.getYangFiles(searchDir));
+        utilManager.parseYangFileInfoSet();
+        utilManager.createYangNodeSet();
+
+        YangNode selfNode = null;
+        YangNode refNode1 = null;
+        YangNode refNode2 = null;
+
+        // Create YANG node set
+        yangLinkerManager.createYangNodeSet(utilManager.getYangNodeSet());
+
+        // Carry out linking of sub module with module.
+        yangLinkerManager.linkSubModulesToParentModule(utilManager.getYangNodeSet());
+
+        // Add references to import list.
+        yangLinkerManager.addRefToYangFilesImportList(utilManager.getYangNodeSet());
+
+        // Add references to include list.
+        yangLinkerManager.addRefToYangFilesIncludeList(utilManager.getYangNodeSet());
+
+        // Carry out inter-file linking.
+        yangLinkerManager.processInterFileLinking(utilManager.getYangNodeSet());
+
+        for (YangNode rootNode : utilManager.getYangNodeSet()) {
+            if (rootNode.getName().equals("syslog3")) {
+                selfNode = rootNode;
+            } else if (rootNode.getName().equals("syslog4")) {
+                refNode1 = rootNode;
+            } else {
+                refNode2 = rootNode;
+            }
+        }
+
+        // Check whether the data model tree returned is of type module.
+        assertThat(selfNode instanceof YangModule, is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(selfNode.getNodeType(), is(MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) selfNode;
+        assertThat(yangNode.getName(), is("syslog3"));
+
+        ListIterator<YangFeature> featureIterator = yangNode.getFeatureList().listIterator();
+        YangFeature feature = featureIterator.next();
+        assertThat(feature.getName(), is("frr-te"));
+
+        YangIfFeature ifFeature = feature.getIfFeatureList().iterator().next();
+        assertThat(ifFeature.getName().getName(), is("p2mp-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(RESOLVED));
+
+        YangContainer container = (YangContainer) selfNode.getChild();
+        assertThat(container.getName(), is("speed"));
+        YangLeaf leaf = container.getListOfLeaf().iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("frr-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(RESOLVED));
+    }
+
+    /**
+     * Checks inter file feature linking with imported file with dependency.
+     */
+    @Test
+    public void processFeatureInImportedFileWithDependency()
+            throws IOException, ParserException, MojoExecutionException {
+
+        String searchDir = "src/test/resources/interfilefeatureimportdependency";
+        utilManager.createYangFileInfoSet(YangFileScanner.getYangFiles(searchDir));
+        utilManager.parseYangFileInfoSet();
+        utilManager.createYangNodeSet();
+
+        YangNode selfNode = null;
+        YangNode refNode1 = null;
+        YangNode refNode2 = null;
+
+        // Create YANG node set
+        yangLinkerManager.createYangNodeSet(utilManager.getYangNodeSet());
+
+        // Add references to import list.
+        yangLinkerManager.addRefToYangFilesImportList(utilManager.getYangNodeSet());
+
+        // Carry out inter-file linking.
+        yangLinkerManager.processInterFileLinking(utilManager.getYangNodeSet());
+
+        for (YangNode rootNode : utilManager.getYangNodeSet()) {
+            if (rootNode.getName().equals("syslog1")) {
+                selfNode = rootNode;
+            } else if (rootNode.getName().equals("syslog2")) {
+                refNode1 = rootNode;
+            } else {
+                refNode2 = rootNode;
+            }
+        }
+
+        // Check whether the data model tree returned is of type module.
+        assertThat(selfNode instanceof YangModule, is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(selfNode.getNodeType(), is(MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) selfNode;
+        assertThat(yangNode.getName(), is("syslog1"));
+
+        ListIterator<YangFeature> featureIterator = yangNode.getFeatureList().listIterator();
+        YangFeature feature = featureIterator.next();
+        assertThat(feature.getName(), is("frr-te"));
+
+        YangIfFeature ifFeature = feature.getIfFeatureList().iterator().next();
+        assertThat(ifFeature.getName().getName(), is("p2mp-te"));
+        assertThat(ifFeature.getName().getPrefix(), is("sys2"));
+        assertThat(ifFeature.getResolvableStatus(), is(RESOLVED));
+
+        YangContainer container = (YangContainer) selfNode.getChild();
+        assertThat(container.getName(), is("speed"));
+        YangLeaf leaf = container.getListOfLeaf().iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("frr-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(RESOLVED));
+    }
+
+    /**
+     * Checks inter file feature linking with included file with dependency.
+     */
+    @Test
+    public void processFeatureInIncludedFileWithDependency()
+            throws IOException, ParserException, MojoExecutionException {
+
+        String searchDir = "src/test/resources/interfilefeatureincludedependency";
+        utilManager.createYangFileInfoSet(YangFileScanner.getYangFiles(searchDir));
+        utilManager.parseYangFileInfoSet();
+        utilManager.createYangNodeSet();
+
+        YangNode selfNode = null;
+        YangNode refNode1 = null;
+        YangNode refNode2 = null;
+
+        // Create YANG node set
+        yangLinkerManager.createYangNodeSet(utilManager.getYangNodeSet());
+
+        // Carry out linking of sub module with module.
+        yangLinkerManager.linkSubModulesToParentModule(utilManager.getYangNodeSet());
+
+        // Add references to include list.
+        yangLinkerManager.addRefToYangFilesIncludeList(utilManager.getYangNodeSet());
+
+        // Add references to import list.
+        yangLinkerManager.addRefToYangFilesImportList(utilManager.getYangNodeSet());
+
+        // Carry out inter-file linking.
+        yangLinkerManager.processInterFileLinking(utilManager.getYangNodeSet());
+
+        for (YangNode rootNode : utilManager.getYangNodeSet()) {
+            if (rootNode.getName().equals("syslog1")) {
+                selfNode = rootNode;
+            } else if (rootNode.getName().equals("syslog2")) {
+                refNode1 = rootNode;
+            } else {
+                refNode2 = rootNode;
+            }
+        }
+
+        // Check whether the data model tree returned is of type module.
+        assertThat(selfNode instanceof YangModule, is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(selfNode.getNodeType(), is(MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) selfNode;
+        assertThat(yangNode.getName(), is("syslog1"));
+
+        ListIterator<YangFeature> featureIterator = yangNode.getFeatureList().listIterator();
+        YangFeature feature = featureIterator.next();
+        assertThat(feature.getName(), is("frr-te"));
+
+        YangIfFeature ifFeature = feature.getIfFeatureList().iterator().next();
+        assertThat(ifFeature.getName().getName(), is("p2mp-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(RESOLVED));
+
+        YangContainer container = (YangContainer) selfNode.getChild();
+        assertThat(container.getName(), is("speed"));
+        YangLeaf leaf = container.getListOfLeaf().iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("frr-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(RESOLVED));
+    }
+
+    /**
+     * Checks inter file feature linking with imported file with dependency
+     * feature undefined.
+     */
+    @Test
+    public void processFeatureInImportedFileWithDependencyUndefined()
+            throws IOException, ParserException, MojoExecutionException {
+
+        String searchDir = "src/test/resources/interfilefeatureimportdependencyUndefined";
+        utilManager.createYangFileInfoSet(YangFileScanner.getYangFiles(searchDir));
+        utilManager.parseYangFileInfoSet();
+        utilManager.createYangNodeSet();
+
+        YangNode selfNode = null;
+        YangNode refNode1 = null;
+        YangNode refNode2 = null;
+
+        // Create YANG node set
+        yangLinkerManager.createYangNodeSet(utilManager.getYangNodeSet());
+
+        // Add references to import list.
+        yangLinkerManager.addRefToYangFilesImportList(utilManager.getYangNodeSet());
+
+        // Carry out inter-file linking.
+        yangLinkerManager.processInterFileLinking(utilManager.getYangNodeSet());
+
+        for (YangNode rootNode : utilManager.getYangNodeSet()) {
+            if (rootNode.getName().equals("syslog1")) {
+                selfNode = rootNode;
+            } else if (rootNode.getName().equals("syslog2")) {
+                refNode1 = rootNode;
+            } else {
+                refNode2 = rootNode;
+            }
+        }
+
+        // Check whether the data model tree returned is of type module.
+        assertThat(selfNode instanceof YangModule, is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(selfNode.getNodeType(), is(MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) selfNode;
+        assertThat(yangNode.getName(), is("syslog1"));
+
+        ListIterator<YangFeature> featureIterator = yangNode.getFeatureList().listIterator();
+        YangFeature feature = featureIterator.next();
+        assertThat(feature.getName(), is("frr-te"));
+
+        YangIfFeature ifFeature = feature.getIfFeatureList().iterator().next();
+        assertThat(ifFeature.getName().getName(), is("p2mp-te"));
+        assertThat(ifFeature.getName().getPrefix(), is("sys2"));
+        assertThat(ifFeature.getResolvableStatus(), is(INTRA_FILE_RESOLVED));
+
+        YangContainer container = (YangContainer) selfNode.getChild();
+        assertThat(container.getName(), is("speed"));
+        YangLeaf leaf = container.getListOfLeaf().iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("frr-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(INTRA_FILE_RESOLVED));
+    }
+
+    /**
+     * Checks inter file feature linking with included file with dependency
+     * feature undefined.
+     */
+    @Test
+    public void processFeatureInIncludedFileWithDependencyUndefined()
+            throws IOException, ParserException, MojoExecutionException {
+
+        String searchDir = "src/test/resources/interfilefeatureincludedependencyUndefined";
+        utilManager.createYangFileInfoSet(YangFileScanner.getYangFiles(searchDir));
+        utilManager.parseYangFileInfoSet();
+        utilManager.createYangNodeSet();
+
+        YangNode selfNode = null;
+        YangNode refNode1 = null;
+        YangNode refNode2 = null;
+
+        // Create YANG node set
+        yangLinkerManager.createYangNodeSet(utilManager.getYangNodeSet());
+
+        // Carry out linking of sub module with module.
+        yangLinkerManager.linkSubModulesToParentModule(utilManager.getYangNodeSet());
+
+        // Add references to import list.
+        yangLinkerManager.addRefToYangFilesImportList(utilManager.getYangNodeSet());
+
+        // Add references to include list.
+        yangLinkerManager.addRefToYangFilesIncludeList(utilManager.getYangNodeSet());
+
+        // Carry out inter-file linking.
+        yangLinkerManager.processInterFileLinking(utilManager.getYangNodeSet());
+
+        for (YangNode rootNode : utilManager.getYangNodeSet()) {
+            if (rootNode.getName().equals("syslog1")) {
+                selfNode = rootNode;
+            } else if (rootNode.getName().equals("syslog2")) {
+                refNode1 = rootNode;
+            } else {
+                refNode2 = rootNode;
+            }
+        }
+
+        // Check whether the data model tree returned is of type module.
+        assertThat(selfNode instanceof YangModule, is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(selfNode.getNodeType(), is(MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) selfNode;
+        assertThat(yangNode.getName(), is("syslog1"));
+
+        ListIterator<YangFeature> featureIterator = yangNode.getFeatureList().listIterator();
+        YangFeature feature = featureIterator.next();
+        assertThat(feature.getName(), is("frr-te"));
+
+        YangIfFeature ifFeature = feature.getIfFeatureList().iterator().next();
+        assertThat(ifFeature.getName().getName(), is("p2mp-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(INTRA_FILE_RESOLVED));
+
+        YangContainer container = (YangContainer) selfNode.getChild();
+        assertThat(container.getName(), is("speed"));
+        YangLeaf leaf = container.getListOfLeaf().iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("frr-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(INTRA_FILE_RESOLVED));
+    }
+}
+

+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.plugin.manager;
+
+import java.io.IOException;
+import java.util.List;
+import org.junit.Test;
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangFeature;
+import org.onosproject.yangutils.datamodel.YangIfFeature;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangNodeType;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.datamodel.utils.ResolvableStatus;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+
+/**
+ * Test cases for testing if-feature intra file linking.
+ */
+public class IntraFileIfFeatureLinkingTest {
+
+    private final YangUtilsParserManager manager = new YangUtilsParserManager();
+
+    /**
+     * Checks self resolution when feature defined in same file.
+     */
+    @Test
+    public void processSelfFileLinkingWithFeature()
+            throws IOException, ParserException {
+
+        YangNode node = manager
+                .getDataModel("src/test/resources/SelfFileLinkingWithFeature.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("syslog"));
+
+        List<YangFeature> featureList = yangNode.getFeatureList();
+        YangFeature feature = featureList.iterator().next();
+        assertThat(feature.getName(), is("local-storage"));
+
+        YangContainer container = (YangContainer) yangNode.getChild();
+        assertThat(container.getName(), is("speed"));
+
+        List<YangLeaf> listOfLeaf = container.getListOfLeaf();
+        YangLeaf leaf = listOfLeaf.iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        YangIfFeature ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("local-storage"));
+        assertThat(ifFeature.getResolvableStatus(), is(ResolvableStatus.RESOLVED));
+    }
+
+    /**
+     * Checks self resolution when feature is undefined.
+     */
+    @Test
+    public void processSelfFileLinkingWithFeatureUndefined()
+            throws IOException, ParserException {
+
+        YangNode node = manager
+                .getDataModel("src/test/resources/SelfFileLinkingWithFeatureUndefined.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("syslog"));
+
+        YangContainer container = (YangContainer) yangNode.getChild();
+        assertThat(container.getName(), is("speed"));
+
+        List<YangLeaf> listOfLeaf = container.getListOfLeaf();
+        YangLeaf leaf = listOfLeaf.iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        YangIfFeature ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("local-storage"));
+        assertThat(ifFeature.getResolvableStatus(), is(ResolvableStatus.INTRA_FILE_RESOLVED));
+    }
+
+    /**
+     * Checks self resolution of feature with multiple dependency.
+     */
+    @Test
+    public void processSelfFileLinkingWithMultipleDependency() throws IOException, ParserException {
+        YangNode node = manager
+                .getDataModel("src/test/resources/SelfFileLinkingWithMultipleDependency.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("syslog"));
+
+        List<YangFeature> featureList = yangNode.getFeatureList();
+        YangFeature feature = featureList.iterator().next();
+        assertThat(feature.getName(), is("p2mp-te"));
+
+        YangContainer container = (YangContainer) yangNode.getChild();
+        assertThat(container.getName(), is("speed"));
+
+        List<YangLeaf> listOfLeaf = container.getListOfLeaf();
+        YangLeaf leaf = listOfLeaf.iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        YangIfFeature ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("frr-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(ResolvableStatus.RESOLVED));
+    }
+
+    /**
+     * Checks self resolution of feature with multiple dependency undefined.
+     */
+    @Test
+    public void processSelfFileLinkingWithMultipleDependencyUnresolved() throws IOException, ParserException {
+        YangNode node = manager
+                .getDataModel("src/test/resources/SelfFileLinkingWithMultipleDependencyUnresolved.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangModule yangNode = (YangModule) node;
+        assertThat(yangNode.getName(), is("syslog"));
+
+        List<YangFeature> featureList = yangNode.getFeatureList();
+        YangFeature feature = featureList.iterator().next();
+        assertThat(feature.getName(), is("frr-te"));
+
+        YangContainer container = (YangContainer) yangNode.getChild();
+        assertThat(container.getName(), is("speed"));
+
+        List<YangLeaf> listOfLeaf = container.getListOfLeaf();
+        YangLeaf leaf = listOfLeaf.iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        YangIfFeature ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("frr-te"));
+        assertThat(ifFeature.getResolvableStatus(), is(ResolvableStatus.INTRA_FILE_RESOLVED));
+    }
+
+    /**
+     * Checks self resolution when feature is defined in same file in submodule.
+     */
+    @Test
+    public void processSelfFileLinkingWithFeatureInSubModule()
+            throws IOException, ParserException {
+
+        YangNode node = manager
+                .getDataModel("src/test/resources/SelfFileLinkingWithFeatureInSubModule.yang");
+
+        // Check whether the data model tree returned is of type module.
+        assertThat((node instanceof YangSubModule), is(true));
+
+        // Check whether the node type is set properly to module.
+        assertThat(node.getNodeType(), is(YangNodeType.SUB_MODULE_NODE));
+
+        // Check whether the module name is set correctly.
+        YangSubModule yangNode = (YangSubModule) node;
+        assertThat(yangNode.getName(), is("syslog"));
+
+        List<YangFeature> featureList = yangNode.getFeatureList();
+        YangFeature feature = featureList.iterator().next();
+        assertThat(feature.getName(), is("local-storage"));
+
+        YangContainer container = (YangContainer) yangNode.getChild();
+        assertThat(container.getName(), is("speed"));
+
+        List<YangLeaf> listOfLeaf = container.getListOfLeaf();
+        YangLeaf leaf = listOfLeaf.iterator().next();
+        assertThat(leaf.getName(), is("local-storage-limit"));
+
+        List<YangIfFeature> ifFeatureList = leaf.getIfFeatureList();
+        YangIfFeature ifFeature = ifFeatureList.iterator().next();
+        assertThat(ifFeature.getName().getName(), is("local-storage"));
+        assertThat(ifFeature.getResolvableStatus(), is(ResolvableStatus.RESOLVED));
+    }
+}

@@ -20,6 +20,9 @@ import java.io.File;
 import java.io.IOException;
 import java.io.IOException;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.InvocationTargetException;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.Date;
 import org.junit.Rule;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 import org.junit.rules.ExpectedException;
@@ -104,6 +107,8 @@ public final class JavaIdentifierSyntaxTest {
     private static final String WITH_SMALL = "test_this";
     private static final String WITH_SMALL = "test_this";
     private static final String WITH_CAMEL_CASE_WITH_PREFIX = "123addPrefixTry";
     private static final String WITH_CAMEL_CASE_WITH_PREFIX = "123addPrefixTry";
     private static final String WITH_CAMEL_CASE_WITH_PREFIX1 = "abc1234567890Ss1123G123Gaa";
     private static final String WITH_CAMEL_CASE_WITH_PREFIX1 = "abc1234567890Ss1123G123Gaa";
+    private static final String DATE_FORMAT = "yyyy-MM-dd";
+    private static SimpleDateFormat simpleDateFormat = new SimpleDateFormat(DATE_FORMAT);
     private static YangToJavaNamingConflictUtil conflictResolver = new YangToJavaNamingConflictUtil();
     private static YangToJavaNamingConflictUtil conflictResolver = new YangToJavaNamingConflictUtil();
     private static final String BASE_DIR_PKG = "target.UnitTestCase.";
     private static final String BASE_DIR_PKG = "target.UnitTestCase.";
     private static final String DIR_PATH = "exist1.exist2.exist3";
     private static final String DIR_PATH = "exist1.exist2.exist3";
@@ -140,9 +145,10 @@ public final class JavaIdentifierSyntaxTest {
      * Unit test for root package generation with revision complexity.
      * Unit test for root package generation with revision complexity.
      */
      */
     @Test
     @Test
-    public void getRootPackageTest() {
+    public void getRootPackageTest() throws ParseException {
         conflictResolver.setPrefixForIdentifier(null);
         conflictResolver.setPrefixForIdentifier(null);
-        String rootPackage = getRootPackage((byte) 1, CHILD_PACKAGE, DATE1, conflictResolver);
+        Date date = simpleDateFormat.parse(DATE1);
+        String rootPackage = getRootPackage((byte) 1, CHILD_PACKAGE, date, conflictResolver);
         assertThat(rootPackage.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
         assertThat(rootPackage.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
                 + PERIOD + CHILD_WITH_PERIOD + PERIOD + DATE_WITH_REV1), is(true));
                 + PERIOD + CHILD_WITH_PERIOD + PERIOD + DATE_WITH_REV1), is(true));
     }
     }
@@ -151,31 +157,34 @@ public final class JavaIdentifierSyntaxTest {
      * Unit test for root package generation with invalid prefix.
      * Unit test for root package generation with invalid prefix.
      */
      */
     @Test
     @Test
-    public void getRootPackageWithInvalidPrefix() throws TranslatorException {
+    public void getRootPackageWithInvalidPrefix() throws TranslatorException, ParseException {
         thrown.expect(TranslatorException.class);
         thrown.expect(TranslatorException.class);
         thrown.expectMessage("The given prefix in pom.xml is invalid.");
         thrown.expectMessage("The given prefix in pom.xml is invalid.");
         conflictResolver.setPrefixForIdentifier(INVALID_PREFIX);
         conflictResolver.setPrefixForIdentifier(INVALID_PREFIX);
-        String rootPackage1 = getRootPackage((byte) 1, INVALID_NAME_SPACE_FOR_INVALID_PREFIX, DATE1, conflictResolver);
+        Date date = simpleDateFormat.parse(DATE1);
+        String rootPackage1 = getRootPackage((byte) 1, INVALID_NAME_SPACE_FOR_INVALID_PREFIX, date,
+                conflictResolver);
     }
     }
 
 
     /**
     /**
      * Unit test for root package generation with special characters presence.
      * Unit test for root package generation with special characters presence.
      */
      */
     @Test
     @Test
-    public void getRootPackageWithSpecialCharactersTest() {
+    public void getRootPackageWithSpecialCharactersTest() throws ParseException {
         conflictResolver.setPrefixForIdentifier(VALID_PREFIX);
         conflictResolver.setPrefixForIdentifier(VALID_PREFIX);
-        String rootPackage = getRootPackage((byte) 1, INVALID_NAME_SPACE1, DATE1, conflictResolver);
+        Date date = simpleDateFormat.parse(DATE1);
+        String rootPackage = getRootPackage((byte) 1, INVALID_NAME_SPACE1, date, conflictResolver);
         assertThat(rootPackage.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
         assertThat(rootPackage.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
                 + PERIOD + VALID_NAME_SPACE1 + PERIOD + DATE_WITH_REV1), is(true));
                 + PERIOD + VALID_NAME_SPACE1 + PERIOD + DATE_WITH_REV1), is(true));
         conflictResolver.setPrefixForIdentifier(null);
         conflictResolver.setPrefixForIdentifier(null);
-        String rootPackage1 = getRootPackage((byte) 1, INVALID_NAME_SPACE2, DATE1, conflictResolver);
+        String rootPackage1 = getRootPackage((byte) 1, INVALID_NAME_SPACE2, date, conflictResolver);
         assertThat(rootPackage1.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
         assertThat(rootPackage1.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
                 + PERIOD + VALID_NAME_SPACE2 + PERIOD + DATE_WITH_REV1), is(true));
                 + PERIOD + VALID_NAME_SPACE2 + PERIOD + DATE_WITH_REV1), is(true));
-        String rootPackage2 = getRootPackage((byte) 1, INVALID_NAME_SPACE3, DATE1, conflictResolver);
+        String rootPackage2 = getRootPackage((byte) 1, INVALID_NAME_SPACE3, date, conflictResolver);
         assertThat(rootPackage2.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
         assertThat(rootPackage2.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
                 + PERIOD + VALID_NAME_SPACE4 + PERIOD + DATE_WITH_REV1), is(true));
                 + PERIOD + VALID_NAME_SPACE4 + PERIOD + DATE_WITH_REV1), is(true));
         conflictResolver.setPrefixForIdentifier(INVALID_PREFIX1);
         conflictResolver.setPrefixForIdentifier(INVALID_PREFIX1);
-        String rootPackage3 = getRootPackage((byte) 1, INVALID_NAME_SPACE2, DATE1, conflictResolver);
+        String rootPackage3 = getRootPackage((byte) 1, INVALID_NAME_SPACE2, date, conflictResolver);
         assertThat(rootPackage3.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
         assertThat(rootPackage3.equals(DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER
                 + PERIOD + VALID_NAME_SPACE3 + PERIOD + DATE_WITH_REV1), is(true));
                 + PERIOD + VALID_NAME_SPACE3 + PERIOD + DATE_WITH_REV1), is(true));
 
 
@@ -185,8 +194,9 @@ public final class JavaIdentifierSyntaxTest {
      * Unit test for root package generation without complexity in revision.
      * Unit test for root package generation without complexity in revision.
      */
      */
     @Test
     @Test
-    public void getRootPackageWithRevTest() {
-        String rootPkgWithRev = getRootPackage((byte) 1, CHILD_PACKAGE, DATE2, null);
+    public void getRootPackageWithRevTest() throws ParseException {
+        Date date = simpleDateFormat.parse(DATE2);
+        String rootPkgWithRev = getRootPackage((byte) 1, CHILD_PACKAGE, date, null);
         assertThat(rootPkgWithRev.equals(
         assertThat(rootPkgWithRev.equals(
                 DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER + PERIOD + CHILD_WITH_PERIOD + PERIOD + DATE_WITH_REV2),
                 DEFAULT_BASE_PKG + PERIOD + VERSION_NUMBER + PERIOD + CHILD_WITH_PERIOD + PERIOD + DATE_WITH_REV2),
                 is(true));
                 is(true));

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    container interface {
+        leaf ifType {
+            type enumeration {
+                enum ethernet;
+                enum atm;
+            }
+        }
+        leaf ifMTU {
+            type uint32;
+        }
+        must "ifType != 'ethernet' or " +
+             "(ifType = 'ethernet' and ifMTU = 1500)" {
+            description "An ethernet MTU must be 1500";
+        }
+        must "ifType != 'atm' or " +
+             "(ifType = 'atm' and ifMTU <= 17966 and ifMTU >= 64)" {
+            description "An atm MTU must be  64 .. 17966";
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    list interface-switching-capability {
+         key "switching-capability";
+         description
+           "List of Interface Switching Capabilities Descriptors (ISCD)
+            for this link.";
+         reference
+           "RFC3471: Generalized Multi-Protocol Label Switching (GMPLS)
+            Signaling Functional Description.
+            RFC4203: OSPF Extensions in Support of Generalized
+            Multi-Protocol Label Switching (GMPLS).";
+         leaf switching-capability {
+           type string;
+           description
+             "Switching Capability for this interface.";
+         }
+     }
+     container time-division-multiplex-capable {
+         when "../switching-capability = 'TDM'" {
+             description "Valid only for TDM";
+         }
+         description
+             "Interface has time-division multiplex capabilities.";
+
+         leaf minimum-lsp-bandwidth {
+             type decimal64;
+         }
+     }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    leaf ifType {
+        type enumeration {
+            enum ethernet;
+            enum atm;
+        }
+        must "ifType != 'ethernet'" {
+            description "ifType is not ethernet";
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix Ant;
+    leaf ifType {
+        when "ifType != 'ethernet'" {
+            description "ifType is not ethernet";
+        }
+        type enumeration {
+            enum ethernet;
+            enum atm;
+        }
+    }
+}

+module Test {
+    yang-version 1;
+    namespace urn:ietf:params:xml:ns:yang:ietf-ospf;
+    prefix test;
+
+     revision 2013-07-15 {
+       description
+        "This revision adds the following new data types:
+         - yang-identifier
+         - hex-string
+         - uuid
+         - dotted-quad";
+       reference
+        "RFC 6991: Common YANG Data Types";
+     }
+     revision 2013-07-14 {
+       description
+        "This revision adds the following new data types:
+         - yang-identifier
+         - hex-string
+         - uuid
+         - dotted-quad";
+       reference
+        "RFC 6991: Common YANG Data Types";
+     }
+}

+module syslog {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix "sys";
+    feature local-storage {
+        description
+            "This feature means the device supports local
+             storage (memory, flash or disk) that can be used to
+             store syslog messages.";
+    }
+
+    container speed {
+        leaf local-storage-limit {
+             if-feature local-storage;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                  "The amount of local storage that can be
+                   used to hold syslog messages.";
+         }
+     }
+}

+submodule syslog {
+    yang-version 1;
+    belongs-to "syslog1" {
+        prefix "sys";
+    }
+    feature local-storage {
+        description
+            "This feature means the device supports local
+             storage (memory, flash or disk) that can be used to
+             store syslog messages.";
+    }
+
+    container speed {
+        leaf local-storage-limit {
+             if-feature local-storage;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                 "The amount of local storage that can be
+                  used to hold syslog messages.";
+         }
+    }
+}

+module syslog {
+    yang-version 1;
+    namespace http://huawei.com;
+    prefix "sys";
+
+    container speed {
+        leaf local-storage-limit {
+            if-feature local-storage;
+            type uint64;
+            units "kilobyte";
+            config false;
+            description
+                 "The amount of local storage that can be
+                  used to hold syslog messages.";
+        }
+    }
+}

+module syslog {
+     yang-version 1;
+     namespace http://huawei.com;
+     prefix "sys";
+
+     feature p2mp-te {
+       description "Indicates support for P2MP-TE";
+     }
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature p2mp-te;
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature frr-te;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+module syslog {
+     yang-version 1;
+     namespace http://huawei.com;
+     prefix "sys";
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature p2mp-te;
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature frr-te;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+module syslog {
+     yang-version 1;
+     namespace http://huawei.com;
+     prefix "sys";
+
+     feature p2mp-te {
+       description "Indicates support for P2MP-TE";
+     }
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature p2mp-te;
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature local-storage;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+module syslog1 {
+     yang-version 1;
+     namespace "http://huawei1.com";
+     prefix "sys1";
+
+     import "syslog2" {
+        prefix "sys2";
+     }
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature "sys2:p2mp-te";
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature frr-te;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+module syslog2 {
+     yang-version 1;
+     namespace "http://huawei2.com";
+     prefix "sys2";
+
+     feature p2mp-te {
+       description "Indicates support for P2MP-TE";
+     }
+}

+module syslog1 {
+     yang-version 1;
+     namespace "http://huawei1.com";
+     prefix "sys1";
+
+     import "syslog2" {
+        prefix "sys2";
+     }
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature "sys2:p2mp-te";
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature frr-te;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+module syslog2 {
+     yang-version 1;
+     namespace "http://huawei2.com";
+     prefix "sys2";
+
+     import "syslog3" {
+        prefix "sys3";
+     }
+
+     feature p2mp-te {
+       description "Indicates support for P2MP-TE";
+       if-feature "sys3:extended-admin-groups";
+     }
+}

+module syslog3 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys3";
+
+     feature extended-admin-groups {
+       description
+         "Indicates support for TE link extended admin
+         groups.";
+     }
+}

+module syslog1 {
+     yang-version 1;
+     namespace "http://huawei1.com";
+     prefix "sys1";
+
+     import "syslog2" {
+        prefix "sys2";
+     }
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature "sys2:p2mp-te";
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature frr-te;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+module syslog2 {
+     yang-version 1;
+     namespace "http://huawei2.com";
+     prefix "sys2";
+
+     import "syslog3" {
+        prefix "sys3";
+     }
+
+     feature p2mp-te {
+       description "Indicates support for P2MP-TE";
+       if-feature "sys3:extended-admin-groups";
+     }
+}
+

+module syslog3 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys3";
+}

+module syslog3 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys3";
+
+     include "syslog4";
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature "p2mp-te";
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature frr-te;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+submodule syslog4 {
+     yang-version 1;
+     belongs-to "syslog3" {
+         prefix "sys3";
+     }
+
+     feature p2mp-te {
+       description "Indicates support for P2MP-TE";
+     }
+}

+module syslog1 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys1";
+
+     include "syslog2";
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature "p2mp-te";
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature frr-te;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+submodule syslog2 {
+     yang-version 1;
+     belongs-to "syslog1" {
+         prefix "sys1";
+     }
+     
+     import "syslog3" {
+        prefix "sys3";
+     }
+
+     feature p2mp-te {
+       description "Indicates support for P2MP-TE";
+       if-feature "sys3:extended-admin-groups";
+     }
+}
+

+module syslog3 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys3";
+
+     feature extended-admin-groups {
+       description
+         "Indicates support for TE link extended admin
+         groups.";
+     }
+}

+module syslog1 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys1";
+
+     include "syslog2";
+
+     feature frr-te {
+       description "Indicates support for TE FastReroute (FRR)";
+       if-feature "p2mp-te";
+     }
+
+     container speed {
+         leaf local-storage-limit {
+             if-feature frr-te;
+             type uint64;
+             units "kilobyte";
+             config false;
+             description
+                     "The amount of local storage that can be
+                      used to hold syslog messages.";
+         }
+     }
+}

+submodule syslog2 {
+     yang-version 1;
+     belongs-to "syslog1" {
+         prefix "sys1";
+     }
+     
+     import "syslog3" {
+        prefix "sys3";
+     }
+
+     feature p2mp-te {
+       description "Indicates support for P2MP-TE";
+       if-feature "sys3:extended-admin-groups";
+     }
+}
+

+module syslog3 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys3";
+}

@@ -68,7 +68,7 @@
       * Features
       * Features
       */
       */
 
 
-     /*feature configuration-schedule {
+     feature configuration-schedule {
        description
        description
          "This feature indicates that the system supports
          "This feature indicates that the system supports
           configuration scheduling.";
           configuration scheduling.";
@@ -91,7 +91,7 @@
        description
        description
          "This feature indicates that the system supports
          "This feature indicates that the system supports
           template configuration.";
           template configuration.";
-     }*/
+     }
 
 
      /*
      /*
       * Typedefs
       * Typedefs

@@ -257,7 +257,7 @@
      }*/
      }*/
 
 
      /* TE basic features */
      /* TE basic features */
-     /*feature p2mp-te {
+     feature p2mp-te {
        description
        description
          "Indicates support for P2MP-TE";
          "Indicates support for P2MP-TE";
      }
      }
@@ -291,7 +291,7 @@
      feature named-path-constraints {
      feature named-path-constraints {
        description
        description
          "Indicates support for named path constraints";
          "Indicates support for named path constraints";
-     }*/
+     }
 
 
      grouping explicit-route-subobject {
      grouping explicit-route-subobject {
        description
        description