diff --git a/src/interest-container.hpp b/src/interest-container.hpp
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+/* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2012-2014 University of California, Los Angeles
+ *
+ * This file is part of ChronoSync, synchronization library for distributed realtime
+ * applications for NDN.
+ *
+ * ChronoSync 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.
+ *
+ * ChronoSync 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
+ * ChronoSync, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @author Zhenkai Zhu <http://irl.cs.ucla.edu/~zhenkai/>
+ * @author Chaoyi Bian <bcy@pku.edu.cn>
+ * @author Alexander Afanasyev <http://lasr.cs.ucla.edu/afanasyev/index.html>
+ * @author Yingdi Yu <yingdi@cs.ucla.edu>
+ */
+
+#ifndef CHRONOSYNC_INTEREST_CONTAINER_HPP
+#define CHRONOSYNC_INTEREST_CONTAINER_HPP
+
+#include "common.hpp"
+#include "mi-tag.hpp"
+#include "diff-state-container.hpp"
+
+#include <ndn-cxx/util/time.hpp>
+#include <ndn-cxx/util/scheduler.hpp>
+
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/tag.hpp>
+#include <boost/multi_index/hashed_index.hpp>
+#include <boost/multi_index/ordered_index.hpp>
+#include <boost/multi_index/member.hpp>
+
+namespace chronosync {
+
+namespace mi = boost::multi_index;
+
+/// @brief Entry to record unsatisfied Sync Interest
+class UnsatisfiedInterest : noncopyable
+{
+public:
+  UnsatisfiedInterest(shared_ptr<const Interest> interest,
+                      ndn::ConstBufferPtr digest,
+                      bool isUnknown = false);
+
+public:
+  shared_ptr<const Interest> interest;
+  ndn::ConstBufferPtr        digest;
+  bool                       isUnknown;
+  ndn::EventId               expirationEvent;
+};
+
+typedef boost::shared_ptr<UnsatisfiedInterest> UnsatisfiedInterestPtr;
+typedef boost::shared_ptr<const UnsatisfiedInterest> ConstUnsatisfiedInterestPtr;
+
+/**
+ * @brief Container for unsatisfied Sync Interests
+ */
+struct InterestContainer : public mi::multi_index_container<
+  UnsatisfiedInterestPtr,
+  mi::indexed_by<
+    mi::hashed_unique<
+      mi::tag<hashed>,
+      mi::member<UnsatisfiedInterest, ndn::ConstBufferPtr, &UnsatisfiedInterest::digest>,
+      DigestPtrHash,
+      DigestPtrEqual
+      >
+    >
+  >
+{
+};
+
+} // namespace chronosync
+
+#endif // CHRONOSYNC_INTEREST_CONTAINER_HPP