[ONOS-5076] YANG data tree Builder

Change-Id: I25160b651c26e614d29d7fad85e63f77a262d77c
diff --git a/apps/yms/app/src/main/java/org/onosproject/yms/app/ydt/YdtExtendedWalker.java b/apps/yms/app/src/main/java/org/onosproject/yms/app/ydt/YdtExtendedWalker.java
new file mode 100644
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+++ b/apps/yms/app/src/main/java/org/onosproject/yms/app/ydt/YdtExtendedWalker.java
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+/*
+ * 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.yms.app.ydt;
+
+import org.onosproject.yms.ydt.YdtWalker;
+
+/**
+ * Abstraction of an entity which provides interfaces for YDT extended walker.
+ */
+public interface YdtExtendedWalker extends YdtWalker {
+
+    /**
+     * Walks the YANG data tree. Protocols implements YDT listener service and
+     * walks YDT tree with input as implemented object.
+     * YDT walker provides call backs to implemented methods.
+     *
+     * @param ydtListener YDT listener implemented by the protocol
+     * @param rootNode    root node of YDT
+     */
+    void walk(YdtExtendedListener ydtListener, YdtExtendedContext rootNode);
+}