diff --git a/src/clients/iterative-query-controller.hpp b/src/clients/iterative-query-controller.hpp
index 83bf856..a04424e 100644
--- a/src/clients/iterative-query-controller.hpp
+++ b/src/clients/iterative-query-controller.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2017, Regents of the University of California.
+ * Copyright (c) 2014-2018, 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.
@@ -79,6 +79,11 @@
   void
   onData(const ndn::Interest& interest, const Data& data);
 
+  /**
+   * @brief called when any data are validated.
+   * It will unwrap the NACK record,
+   * so onSucceed callback will be called with only inner DoE
+   */
   void
   onDataValidated(const Data& data, NdnsContentType contentType);
 
@@ -130,6 +135,10 @@
     return m_nTryComps;
   }
 
+private:
+  bool
+  isAbsentByDoe(const Data& data) const;
+
 protected:
   security::v2::Validator* m_validator;
   /**
@@ -151,6 +160,8 @@
 
 private:
   Block m_lastLink;
+  Data m_doe;
+  Name m_lastLabelType;
   ndn::InMemoryStorage* m_nsCache;
 };