diff --git a/src/validator.hpp b/src/validator.hpp
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+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014, Regents of the University of California.
+ *
+ * This file is part of NDNS (Named Data Networking Domain Name Service).
+ * See AUTHORS.md for complete list of NDNS authors and contributors.
+ *
+ * NDNS is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * NDNS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * NDNS, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef NDNS_VALIDATOR_HPP
+#define NDNS_VALIDATOR_HPP
+
+#include "config.hpp"
+
+#include "ndn-cxx/data.hpp"
+#include <ndn-cxx/security/validator-config.hpp>
+
+
+namespace ndn {
+namespace ndns {
+
+/**
+ * @brief NDNS validator, which validates Data with hierarchical way. Validator is used in three
+ * scenarios:
+ * 1) Dig client gets the final response Data;
+ * 2) Authoritative name server receives update request;
+ * 3) Update client gets the result of update request.
+ *
+ * @note Compared to its parent class, ValidatorConfig, the class provides is customized according
+ * to config file and the above working scenarios:
+ * 1) give the default path of config file;
+ * 2) default rule is the given path if not valid or the content is wrong.
+ *    Validator rule is must for NDNS, the daemon/dig/update must work even without manually edit
+ * 3) some wrapper provides default behavior when verification succeeds or fails
+ */
+class Validator : public ValidatorConfig
+{
+
+public:
+  static std::string VALIDATOR_CONF_FILE;
+
+  /**
+   * @brief the callback function which is called after validation finishes
+   * @param[in] callback The function is called after validation finishes, no matter validation
+   * succeeds or fails
+   */
+  explicit
+  Validator(Face& face, const std::string& confFile = VALIDATOR_CONF_FILE);
+
+  /**
+   * @brief validate the Data
+   */
+  virtual void
+  validate(const Data& data,
+           const OnDataValidated& onValidated,
+           const OnDataValidationFailed& onValidationFailed);
+
+private:
+  /**
+   * @brief the default callback function on data validated
+   */
+  void
+  onDataValidated(const shared_ptr<const Data>& data);
+
+  /**
+   * @brief the default callback function on data validation failed
+   */
+  void
+  onDataValidationFailed(const shared_ptr<const Data>& data, const std::string& str);
+
+};
+
+
+} // namespace ndns
+} // namespace ndn
+
+#endif // NDNS_VALIDATOR_HPP