diff --git a/apps/yms/api/src/main/java/org/onosproject/yms/ydt/package-info.java b/apps/yms/api/src/main/java/org/onosproject/yms/ydt/package-info.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.
+ */
+
+/**
+ * Provides interfaces to build and obtain YANG data tree which is data
+ * (sub)instance representation, abstract of protocol.
+ *
+ * NBI protocol implementation takes care of the protocol specific
+ * operations. They are abstracted from the intricacies of understanding
+ * the application identification or handling the interaction with
+ * applications.
+ *
+ * NBI protocols need to handle the encoding and decoding of data to the
+ * protocol specific format. They are unaware of the YANG of applications,
+ * i.e. protocols are unaware of the data structure / organization in
+ * applications.
+ *
+ * They need to translate the protocol operation request, into a protocol
+ * independent abstract tree called the YANG data tree (YDT). In order to
+ * enable the protocol in building these abstract data tree, YANG
+ * management system provides a utility called the YANG data tree builder.
+ *
+ * Using the YANG data tree utility API's protocols are expected to walk
+ * the data received in request and pass the information during the walk.
+ * YANG data tree builder, identifies the application which supports the
+ * request and validates it against the schema defined in YANG, and
+ * constructs the abstract YANG data tree.
+ */
+package org.onosproject.yms.ydt;