11 files changed, 587 insertions, 257 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 50edfaf..d884224 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,7 +8,7 @@ find_package(DL REQUIRED)
 find_package(Readline REQUIRED)
 #find_package(KRB5 REQUIRED gssapi)
 find_package(OpenSSL REQUIRED)
-find_package(Boost REQUIRED regex signals system thread)
+find_package(Boost REQUIRED date_time regex signals system thread)
 find_package(MySQL)
 
 configure_file(${MAD_SOURCE_DIR}/config.h.in ${MAD_BINARY_DIR}/config.h)
diff --git a/src/Common/Backends/NetworkUserBackend.cpp b/src/Common/Backends/NetworkUserBackend.cpp
index f75783c..27f65f5 100644
--- a/src/Common/Backends/NetworkUserBackend.cpp
+++ b/src/Common/Backends/NetworkUserBackend.cpp
@@ -20,15 +20,30 @@
 #include "NetworkUserBackend.h"
 #include "../RequestManager.h"
 
+#include <boost/date_time/posix_time/posix_time.hpp>
+
 namespace Mad {
 namespace Common {
 namespace Backends {
 
+void NetworkUserBackend::SimpleUserRequest::sendRequest() {
+  Common::XmlPacket packet;
+  packet.setType(type);
+
+  if(!timestamp.is_not_a_date_time())
+    packet.set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
+  sendPacket(packet);
+}
+
 void NetworkUserBackend::IdUserRequest::sendRequest() {
   Common::XmlPacket packet;
   packet.setType(type);
   packet.set(idType, id);
 
+  if(!timestamp.is_not_a_date_time())
+    packet.set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
   sendPacket(packet);
 }
 
@@ -37,22 +52,33 @@ void NetworkUserBackend::NameUserRequest::sendRequest() {
   packet.setType(type);
   packet.set("name", name);
 
+  if(!timestamp.is_not_a_date_time())
+    packet.set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
   sendPacket(packet);
 }
 
-boost::shared_ptr<const std::map<unsigned long, UserInfo> > NetworkUserBackend::getUserList() throw(Core::Exception) {
-  boost::shared_ptr<SimpleUserRequest> request(new SimpleUserRequest(application, "ListUsers"));
+boost::shared_ptr<const std::map<unsigned long, UserInfo> > NetworkUserBackend::getUserList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<SimpleUserRequest> request(new SimpleUserRequest(application, "ListUsers", timestamp));
   application->getRequestManager()->sendRequest(connection, request);
+
   request->wait();
 
   std::pair<boost::shared_ptr<const XmlPacket>, Core::Exception> result = request->getResult();
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<std::map<unsigned long, UserInfo> > userList(new std::map<unsigned long, UserInfo>);
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
 
   const XmlPacket::List *users = result.first->getList("users");
   if(users) {
+    boost::shared_ptr<std::map<unsigned long, UserInfo> > userList(new std::map<unsigned long, UserInfo>);
+
     for(XmlPacket::List::const_iterator user = users->begin(); user != users->end(); ++user) {
       UserInfo userInfo(user->get<unsigned long>("uid"), user->get<const std::string&>("username"));
       userInfo.setGid(user->get<unsigned long>("gid"));
@@ -60,13 +86,15 @@ boost::shared_ptr<const std::map<unsigned long, UserInfo> > NetworkUserBackend::
 
       userList->insert(std::make_pair(userInfo.getUid(), userInfo));
     }
+
+    return userList;
   }
 
-  return userList;
+  return boost::shared_ptr<const std::map<unsigned long, UserInfo> >();
 }
 
-boost::shared_ptr<const UserInfo> NetworkUserBackend::getUserInfo(unsigned long uid) throw(Core::Exception) {
-  boost::shared_ptr<IdUserRequest> request(new IdUserRequest(application, "GetUserInfo", "uid", uid));
+boost::shared_ptr<const UserInfo> NetworkUserBackend::getUserInfo(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<IdUserRequest> request(new IdUserRequest(application, "GetUserInfo", "uid", uid, timestamp));
   application->getRequestManager()->sendRequest(connection, request);
   request->wait();
 
@@ -74,15 +102,29 @@ boost::shared_ptr<const UserInfo> NetworkUserBackend::getUserInfo(unsigned long
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<UserInfo> userInfo(new UserInfo(result.first->get<unsigned long>("uid"), result.first->get<const std::string&>("username")));
-  userInfo->setGid(result.first->get<unsigned long>("gid"));
-  userInfo->setFullName(result.first->get<const std::string&>("fullName"));
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
+
+  unsigned long uid2 = result.first->get<unsigned long>("uid");
 
-  return userInfo;
+  if(uid2) {
+    boost::shared_ptr<UserInfo> userInfo(new UserInfo(uid2, result.first->get<const std::string&>("username")));
+
+    userInfo->setGid(result.first->get<unsigned long>("gid"));
+    userInfo->setFullName(result.first->get<const std::string&>("fullName"));
+
+    return userInfo;
+  }
+
+  return boost::shared_ptr<const UserInfo>();
 }
 
-boost::shared_ptr<const UserInfo> NetworkUserBackend::getUserInfoByName(const std::string &name) throw(Core::Exception) {
-  boost::shared_ptr<NameUserRequest> request(new NameUserRequest(application, "GetUserInfo", name));
+boost::shared_ptr<const UserInfo> NetworkUserBackend::getUserInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<NameUserRequest> request(new NameUserRequest(application, "GetUserInfo", name, timestamp));
   application->getRequestManager()->sendRequest(connection, request);
   request->wait();
 
@@ -90,15 +132,29 @@ boost::shared_ptr<const UserInfo> NetworkUserBackend::getUserInfoByName(const st
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<UserInfo> userInfo(new UserInfo(result.first->get<unsigned long>("uid"), result.first->get<const std::string&>("username")));
-  userInfo->setGid(result.first->get<unsigned long>("gid"));
-  userInfo->setFullName(result.first->get<const std::string&>("fullName"));
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
+
+  unsigned long uid = result.first->get<unsigned long>("uid");
+
+  if(uid) {
+    boost::shared_ptr<UserInfo> userInfo(new UserInfo(uid, result.first->get<const std::string&>("username")));
+
+    userInfo->setGid(result.first->get<unsigned long>("gid"));
+    userInfo->setFullName(result.first->get<const std::string&>("fullName"));
 
-  return userInfo;
+    return userInfo;
+  }
+
+  return boost::shared_ptr<const UserInfo>();
 }
 
-boost::shared_ptr<const std::set<unsigned long> > NetworkUserBackend::getUserGroupList(unsigned long uid) throw(Core::Exception) {
-  boost::shared_ptr<IdUserRequest> request(new IdUserRequest(application, "ListUserGroups", "uid", uid));
+boost::shared_ptr<const std::set<unsigned long> > NetworkUserBackend::getUserGroupList(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<IdUserRequest> request(new IdUserRequest(application, "ListUserGroups", "uid", uid, timestamp));
   application->getRequestManager()->sendRequest(connection, request);
   request->wait();
 
@@ -106,19 +162,29 @@ boost::shared_ptr<const std::set<unsigned long> > NetworkUserBackend::getUserGro
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<std::set<unsigned long> > groupList(new std::set<unsigned long>);
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
 
   const XmlPacket::List *groups = result.first->getList("groups");
+
   if(groups) {
+    boost::shared_ptr<std::set<unsigned long> > groupList(new std::set<unsigned long>);
+
     for(XmlPacket::List::const_iterator group = groups->begin(); group != groups->end(); ++group)
       groupList->insert(group->get<unsigned long>("gid"));
+
+    return groupList;
   }
 
-  return groupList;
+  return boost::shared_ptr<const std::set<unsigned long> >();
 }
 
-boost::shared_ptr<const std::map<unsigned long, GroupInfo> > NetworkUserBackend::getGroupList() throw(Core::Exception) {
-  boost::shared_ptr<SimpleUserRequest> request(new SimpleUserRequest(application, "ListGroups"));
+boost::shared_ptr<const std::map<unsigned long, GroupInfo> > NetworkUserBackend::getGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<SimpleUserRequest> request(new SimpleUserRequest(application, "ListGroups", timestamp));
   application->getRequestManager()->sendRequest(connection, request);
   request->wait();
 
@@ -126,21 +192,30 @@ boost::shared_ptr<const std::map<unsigned long, GroupInfo> > NetworkUserBackend:
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<std::map<unsigned long, GroupInfo> > groupList(new std::map<unsigned long, GroupInfo>);
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
 
   const XmlPacket::List *groups = result.first->getList("groups");
   if(groups) {
+    boost::shared_ptr<std::map<unsigned long, GroupInfo> > groupList(new std::map<unsigned long, GroupInfo>);
+
     for(XmlPacket::List::const_iterator group = groups->begin(); group != groups->end(); ++group) {
       GroupInfo groupInfo(group->get<unsigned long>("gid"), group->get<const std::string&>("name"));
       groupList->insert(std::make_pair(groupInfo.getGid(), groupInfo));
     }
+
+    return groupList;
   }
 
-  return groupList;
+  return boost::shared_ptr<const std::map<unsigned long, GroupInfo> >();
 }
 
-boost::shared_ptr<const GroupInfo> NetworkUserBackend::getGroupInfo(unsigned long gid) throw(Core::Exception) {
-  boost::shared_ptr<IdUserRequest> request(new IdUserRequest(application, "GetGroupInfo", "gid", gid));
+boost::shared_ptr<const GroupInfo> NetworkUserBackend::getGroupInfo(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<IdUserRequest> request(new IdUserRequest(application, "GetGroupInfo", "gid", gid, timestamp));
   application->getRequestManager()->sendRequest(connection, request);
   request->wait();
 
@@ -148,13 +223,23 @@ boost::shared_ptr<const GroupInfo> NetworkUserBackend::getGroupInfo(unsigned lon
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<GroupInfo> groupInfo(new GroupInfo(result.first->get<unsigned long>("gid"), result.first->get<const std::string&>("name")));
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
+
+  unsigned long gid2 = result.first->get<unsigned long>("gid");
 
-  return groupInfo;
+  if(gid2)
+    return boost::shared_ptr<GroupInfo>(new GroupInfo(gid2, result.first->get<const std::string&>("name")));
+
+  return boost::shared_ptr<const GroupInfo>();
 }
 
-boost::shared_ptr<const GroupInfo> NetworkUserBackend::getGroupInfoByName(const std::string &name) throw(Core::Exception) {
-  boost::shared_ptr<NameUserRequest> request(new NameUserRequest(application, "GetGroupInfo", name));
+boost::shared_ptr<const GroupInfo> NetworkUserBackend::getGroupInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<NameUserRequest> request(new NameUserRequest(application, "GetGroupInfo", name, timestamp));
   application->getRequestManager()->sendRequest(connection, request);
   request->wait();
 
@@ -162,13 +247,23 @@ boost::shared_ptr<const GroupInfo> NetworkUserBackend::getGroupInfoByName(const
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<GroupInfo> groupInfo(new GroupInfo(result.first->get<unsigned long>("gid"), result.first->get<const std::string&>("name")));
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
+
+  unsigned long gid = result.first->get<unsigned long>("gid");
 
-  return groupInfo;
+  if(gid)
+    return boost::shared_ptr<GroupInfo>(new GroupInfo(gid, result.first->get<const std::string&>("name")));
+
+  return boost::shared_ptr<const GroupInfo>();
 }
 
-boost::shared_ptr<const std::set<unsigned long> > NetworkUserBackend::getGroupUserList(unsigned long gid) throw(Core::Exception) {
-  boost::shared_ptr<IdUserRequest> request(new IdUserRequest(application, "ListGroupUsers", "gid", gid));
+boost::shared_ptr<const std::set<unsigned long> > NetworkUserBackend::getGroupUserList(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<IdUserRequest> request(new IdUserRequest(application, "ListGroupUsers", "gid", gid, timestamp));
   application->getRequestManager()->sendRequest(connection, request);
   request->wait();
 
@@ -176,20 +271,29 @@ boost::shared_ptr<const std::set<unsigned long> > NetworkUserBackend::getGroupUs
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<std::set<unsigned long> > userList(new std::set<unsigned long>);
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
 
   const XmlPacket::List *users = result.first->getList("users");
   if(users) {
+    boost::shared_ptr<std::set<unsigned long> > userList(new std::set<unsigned long>);
+
     for(XmlPacket::List::const_iterator user = users->begin(); user != users->end(); ++user) {
       userList->insert(user->get<unsigned long>("uid"));
     }
+
+    return userList;
   }
 
-  return userList;
+  return boost::shared_ptr<const std::set<unsigned long> >();
 }
 
-boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > NetworkUserBackend::getFullUserGroupList() throw(Core::Exception) {
-  boost::shared_ptr<SimpleUserRequest> request(new SimpleUserRequest(application, "GetFullUserGroupList"));
+boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > NetworkUserBackend::getFullUserGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::shared_ptr<SimpleUserRequest> request(new SimpleUserRequest(application, "GetFullUserGroupList", timestamp));
   application->getRequestManager()->sendRequest(connection, request);
   request->wait();
 
@@ -197,15 +301,24 @@ boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > NetworkUse
   if(!result.first || result.second)
     throw result.second;
 
-  boost::shared_ptr<std::multimap<unsigned long, unsigned long> > ret(new std::multimap<unsigned long, unsigned long>);
+  if(timestamp) {
+    try {
+      *timestamp = boost::posix_time::from_iso_string(result.first->get<const std::string&>("timestamp"));
+    }
+    catch(...) {}
+  }
 
   const XmlPacket::List *list = result.first->getList("userGroupList");
   if(list) {
+    boost::shared_ptr<std::multimap<unsigned long, unsigned long> > ret(new std::multimap<unsigned long, unsigned long>);
+
     for(XmlPacket::List::const_iterator entry = list->begin(); entry != list->end(); ++entry)
       ret->insert(std::make_pair(entry->get<unsigned long>("uid"), entry->get<unsigned long>("gid")));
+
+    return ret;
   }
 
-  return ret;
+  return boost::shared_ptr<const std::multimap<unsigned long, unsigned long> >();
 }
 
 
diff --git a/src/Common/Backends/NetworkUserBackend.h b/src/Common/Backends/NetworkUserBackend.h
index 66be909..8faa8e3 100644
--- a/src/Common/Backends/NetworkUserBackend.h
+++ b/src/Common/Backends/NetworkUserBackend.h
@@ -21,7 +21,7 @@
 #define MAD_COMMON_BACKENDS_NETWORKUSERBACKEND_H_
 
 #include "../UserBackend.h"
-#include "../Requests/SimpleRequest.h"
+#include "../Request.h"
 
 namespace Mad {
 namespace Common {
@@ -29,9 +29,17 @@ namespace Backends {
 
 class NetworkUserBackend : public UserBackend {
   private:
-    class SimpleUserRequest : public Requests::SimpleRequest {
+    class SimpleUserRequest : public Request {
+      private:
+        std::string type;
+        boost::posix_time::ptime timestamp;
+
+      protected:
+        virtual void sendRequest();
+
       public:
-        SimpleUserRequest(Application *application, const std::string &type) : SimpleRequest(application, type) {}
+        SimpleUserRequest(Application *application, const std::string &type0, boost::posix_time::ptime *timestamp0)
+        : Request(application), type(type0), timestamp(timestamp0 ? *timestamp0 : boost::posix_time::not_a_date_time) {}
     };
 
     class IdUserRequest : public Request {
@@ -39,45 +47,45 @@ class NetworkUserBackend : public UserBackend {
         std::string type;
         std::string idType;
         unsigned long id;
-
+        boost::posix_time::ptime timestamp;
 
       protected:
         virtual void sendRequest();
 
       public:
-        IdUserRequest(Application *application, const std::string &type0, const std::string &idType0, unsigned long id0)
-        : Request(application), type(type0), idType(idType0), id(id0) {}
+        IdUserRequest(Application *application, const std::string &type0, const std::string &idType0, unsigned long id0, boost::posix_time::ptime *timestamp0)
+        : Request(application), type(type0), idType(idType0), id(id0), timestamp(timestamp0 ? *timestamp0 : boost::posix_time::not_a_date_time) {}
     };
 
     class NameUserRequest : public Request {
       private:
         std::string type;
         std::string name;
-
+        boost::posix_time::ptime timestamp;
 
       protected:
         virtual void sendRequest();
 
       public:
-        NameUserRequest(Application *application, const std::string &type0, const std::string &name0)
-        : Request(application), type(type0), name(name0) {}
+        NameUserRequest(Application *application, const std::string &type0, const std::string &name0, boost::posix_time::ptime *timestamp0)
+        : Request(application), type(type0), name(name0), timestamp(timestamp0 ? *timestamp0 : boost::posix_time::not_a_date_time) {}
     };
 
     Application *application;
     Connection *connection;
 
   protected:
-    virtual boost::shared_ptr<const std::map<unsigned long, UserInfo> > getUserList() throw(Core::Exception);
-    virtual boost::shared_ptr<const UserInfo> getUserInfo(unsigned long uid) throw(Core::Exception);
-    virtual boost::shared_ptr<const UserInfo> getUserInfoByName(const std::string &name) throw(Core::Exception);
-    virtual boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> > getUserList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const Common::UserInfo> getUserInfo(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const Common::UserInfo> getUserInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
-    virtual boost::shared_ptr<const std::map<unsigned long, GroupInfo> > getGroupList() throw(Core::Exception);
-    virtual boost::shared_ptr<const GroupInfo> getGroupInfo(unsigned long gid) throw(Core::Exception);
-    virtual boost::shared_ptr<const GroupInfo> getGroupInfoByName(const std::string &name) throw(Core::Exception);
-    virtual boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> > getGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const Common::GroupInfo> getGroupInfo(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const Common::GroupInfo> getGroupInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
-    virtual boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList() throw(Core::Exception);
+    virtual boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
     //virtual void setPassword(unsigned long uid, const std::string &password) throw(Core::Exception);
     //virtual void addUser(const UserInfo &userInfo) throw(Core::Exception);
diff --git a/src/Common/UserBackend.h b/src/Common/UserBackend.h
index 829aae7..4004dbc 100644
--- a/src/Common/UserBackend.h
+++ b/src/Common/UserBackend.h
@@ -31,6 +31,7 @@
 #include <set>
 #include <string>
 
+#include <boost/date_time/posix_time/posix_time_types.hpp>
 #include <boost/smart_ptr.hpp>
 
 
@@ -47,40 +48,40 @@ class UserBackend {
 
     UserBackend() {}
 
-    virtual boost::shared_ptr<const std::map<unsigned long, UserInfo> > getUserList() throw(Core::Exception) {
+    virtual boost::shared_ptr<const std::map<unsigned long, UserInfo> > getUserList(boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
-    virtual boost::shared_ptr<const UserInfo> getUserInfo(unsigned long uid _UNUSED_PARAMETER_) throw(Core::Exception) {
+    virtual boost::shared_ptr<const UserInfo> getUserInfo(unsigned long uid _UNUSED_PARAMETER_, boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
-    virtual boost::shared_ptr<const UserInfo> getUserInfoByName(const std::string &name _UNUSED_PARAMETER_) throw(Core::Exception) {
+    virtual boost::shared_ptr<const UserInfo> getUserInfoByName(const std::string &name _UNUSED_PARAMETER_, boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
-    virtual boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid _UNUSED_PARAMETER_) throw(Core::Exception) {
+    virtual boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid _UNUSED_PARAMETER_, boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
 
-    virtual boost::shared_ptr<const std::map<unsigned long, GroupInfo> > getGroupList() throw(Core::Exception) {
+    virtual boost::shared_ptr<const std::map<unsigned long, GroupInfo> > getGroupList(boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
-    virtual boost::shared_ptr<const GroupInfo> getGroupInfo(unsigned long gid _UNUSED_PARAMETER_) throw(Core::Exception) {
+    virtual boost::shared_ptr<const GroupInfo> getGroupInfo(unsigned long gid _UNUSED_PARAMETER_, boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
-    virtual boost::shared_ptr<const GroupInfo> getGroupInfoByName(const std::string &name _UNUSED_PARAMETER_) throw(Core::Exception) {
+    virtual boost::shared_ptr<const GroupInfo> getGroupInfoByName(const std::string &name _UNUSED_PARAMETER_, boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
-    virtual boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid _UNUSED_PARAMETER_) throw(Core::Exception) {
+    virtual boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid _UNUSED_PARAMETER_, boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
-    virtual boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList() throw(Core::Exception) {
+    virtual boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList(boost::posix_time::ptime *timestamp _UNUSED_PARAMETER_) throw(Core::Exception) {
       throw(Core::Exception(Core::Exception::NOT_IMPLEMENTED));
     }
 
diff --git a/src/Common/UserCache.cpp b/src/Common/UserCache.cpp
index 887e375..a32bcd3 100644
--- a/src/Common/UserCache.cpp
+++ b/src/Common/UserCache.cpp
@@ -23,40 +23,50 @@
 namespace Mad {
 namespace Common {
 
-boost::shared_ptr<const std::map<unsigned long, UserInfo> > UserCache::getUserList() throw(Core::Exception) {
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
-
-  if(users) {
-    application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Using cached user list");
-    return users;
-  }
-  else if(userException) {
-    application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Error cached");
-    throw userException;
-  }
+boost::shared_ptr<const std::map<unsigned long, UserInfo> > UserCache::getUserList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
   try {
-    users = backend->getUserList();
-
-    userNames.reset(new std::map<std::string, unsigned long>);
-    for(std::map<unsigned long, UserInfo>::const_iterator user = users->begin(); user != users->end(); ++user)
-      userNames->insert(std::make_pair(user->second.getUsername(), user->first));
-
-    return users;
+    boost::shared_ptr<const std::map<unsigned long, UserInfo> > newUsers = backend->getUserList(&userTime);
+
+    if(newUsers) {
+      users = newUsers;
+      userException = Core::Exception();
+
+      userNames.reset(new std::map<std::string, unsigned long>);
+      for(std::map<unsigned long, UserInfo>::const_iterator user = users->begin(); user != users->end(); ++user)
+        userNames->insert(std::make_pair(user->second.getUsername(), user->first));
+    }
+    else {
+      if(users)
+        application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Using cached user list");
+      else
+        application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Error cached");
+    }
   }
   catch(Core::Exception e) {
+    users.reset();
     userException = e;
-    throw userException;
   }
-}
 
-boost::shared_ptr<const UserInfo> UserCache::getUserInfo(unsigned long uid) throw(Core::Exception) {
-  getUserList();
+  if((!timestamp) || timestamp->is_not_a_date_time() || (*timestamp < userTime)) {
+    if(timestamp)
+      *timestamp = userTime;
+
+    if(users)
+      return users;
+    else
+      throw userException;
+  }
+
+  return boost::shared_ptr<const std::map<unsigned long, UserInfo> >();
+}
 
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
+boost::shared_ptr<const UserInfo> UserCache::getUserInfo(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
-  if(!users)
-    throw userException;
+  if(!getUserList(timestamp))
+    return boost::shared_ptr<const UserInfo>();
 
   std::map<unsigned long, UserInfo>::const_iterator user = users->find(uid);
 
@@ -66,13 +76,11 @@ boost::shared_ptr<const UserInfo> UserCache::getUserInfo(unsigned long uid) thro
   return boost::shared_ptr<UserInfo>(new UserInfo(user->second));
 }
 
-boost::shared_ptr<const UserInfo> UserCache::getUserInfoByName(const std::string &name) throw(Core::Exception) {
-  getUserList();
+boost::shared_ptr<const UserInfo> UserCache::getUserInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
-
-  if(!users)
-    throw userException;
+  if(!getUserList(timestamp))
+    return boost::shared_ptr<const UserInfo>();
 
   std::map<std::string, unsigned long>::const_iterator uid = userNames->find(name);
   if(uid == userNames->end())
@@ -83,13 +91,11 @@ boost::shared_ptr<const UserInfo> UserCache::getUserInfoByName(const std::string
   return boost::shared_ptr<UserInfo>(new UserInfo(user->second));
 }
 
-boost::shared_ptr<const std::set<unsigned long> > UserCache::getUserGroupList(unsigned long uid) throw(Core::Exception) {
-  getFullUserGroupList();
-
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
+boost::shared_ptr<const std::set<unsigned long> > UserCache::getUserGroupList(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
-  if(!userGroups)
-    throw userGroupException;
+  if(!getFullUserGroupList(timestamp))
+    return boost::shared_ptr<const std::set<unsigned long> >();
 
   std::pair<std::multimap<unsigned long, unsigned long>::const_iterator, std::multimap<unsigned long, unsigned long>::const_iterator> range = userGroups->equal_range(uid);
 
@@ -102,40 +108,50 @@ boost::shared_ptr<const std::set<unsigned long> > UserCache::getUserGroupList(un
 }
 
 
-boost::shared_ptr<const std::map<unsigned long, GroupInfo> > UserCache::getGroupList() throw(Core::Exception) {
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
-
-  if(groups) {
-    application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Using cached group list");
-    return groups;
-  }
-  else if(groupException) {
-    application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Error cached");
-    throw groupException;
-  }
+boost::shared_ptr<const std::map<unsigned long, GroupInfo> > UserCache::getGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
   try {
-    groups = backend->getGroupList();
-
-    groupNames.reset(new std::map<std::string, unsigned long>);
-    for(std::map<unsigned long, GroupInfo>::const_iterator group = groups->begin(); group != groups->end(); ++group)
-      groupNames->insert(std::make_pair(group->second.getName(), group->first));
-
-    return groups;
+    boost::shared_ptr<const std::map<unsigned long, GroupInfo> > newGroups = backend->getGroupList(&groupTime);
+
+    if(newGroups) {
+      groups = newGroups;
+      groupException = Core::Exception();
+
+      groupNames.reset(new std::map<std::string, unsigned long>);
+      for(std::map<unsigned long, GroupInfo>::const_iterator group = groups->begin(); group != groups->end(); ++group)
+        groupNames->insert(std::make_pair(group->second.getName(), group->first));
+    }
+    else {
+      if(groups)
+        application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Using cached group list");
+      else
+        application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Error cached");
+    }
   }
   catch(Core::Exception e) {
+    groups.reset();
     groupException = e;
-    throw groupException;
   }
-}
 
-boost::shared_ptr<const GroupInfo> UserCache::getGroupInfo(unsigned long gid) throw(Core::Exception) {
-  getGroupList();
+  if((!timestamp) || timestamp->is_not_a_date_time() || (*timestamp < groupTime)) {
+    if(timestamp)
+      *timestamp = groupTime;
+
+    if(groups)
+      return groups;
+    else
+      throw groupException;
+  }
+
+  return boost::shared_ptr<const std::map<unsigned long, GroupInfo> >();
+}
 
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
+boost::shared_ptr<const GroupInfo> UserCache::getGroupInfo(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
-  if(!groups)
-    throw groupException;
+  if(!getGroupList(timestamp))
+    return boost::shared_ptr<const GroupInfo>();
 
   std::map<unsigned long, GroupInfo>::const_iterator group = groups->find(gid);
 
@@ -145,13 +161,11 @@ boost::shared_ptr<const GroupInfo> UserCache::getGroupInfo(unsigned long gid) th
   return boost::shared_ptr<GroupInfo>(new GroupInfo(group->second));
 }
 
-boost::shared_ptr<const GroupInfo> UserCache::getGroupInfoByName(const std::string &name) throw(Core::Exception) {
-  getGroupList();
+boost::shared_ptr<const GroupInfo> UserCache::getGroupInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
-
-  if(!groups)
-    throw groupException;
+  if(!getGroupList(timestamp))
+    return boost::shared_ptr<const GroupInfo>();
 
   std::map<std::string, unsigned long>::const_iterator gid = groupNames->find(name);
   if(gid == groupNames->end())
@@ -162,13 +176,11 @@ boost::shared_ptr<const GroupInfo> UserCache::getGroupInfoByName(const std::stri
   return boost::shared_ptr<GroupInfo>(new GroupInfo(group->second));
 }
 
-boost::shared_ptr<const std::set<unsigned long> > UserCache::getGroupUserList(unsigned long gid) throw(Core::Exception) {
-  getFullUserGroupList();
-
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
+boost::shared_ptr<const std::set<unsigned long> > UserCache::getGroupUserList(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
-  if(!userGroups)
-    throw userGroupException;
+  if(!getFullUserGroupList(timestamp))
+    return boost::shared_ptr<const std::set<unsigned long> >();
 
   std::pair<std::multimap<unsigned long, unsigned long>::iterator, std::multimap<unsigned long, unsigned long>::iterator> range = groupUsers->equal_range(gid);
 
@@ -180,30 +192,43 @@ boost::shared_ptr<const std::set<unsigned long> > UserCache::getGroupUserList(un
   return users;
 }
 
-boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > UserCache::getFullUserGroupList() throw(Core::Exception) {
-  boost::lock_guard<boost::shared_mutex> lock(mutex);
+boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > UserCache::getFullUserGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
+  boost::lock_guard<boost::recursive_mutex> lock(mutex);
 
-  if(userGroups) {
-    application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Using cached user-group table");
-    return userGroups;
-  }
-  else if(userGroupException) {
-    application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Error cached");
-    throw userGroupException;
-  }
   try {
-    userGroups = backend->getFullUserGroupList();
-
-    groupUsers.reset(new std::multimap<unsigned long, unsigned long>);
-    for(std::multimap<unsigned long, unsigned long>::const_iterator usergroup = userGroups->begin(); usergroup != userGroups->end(); ++usergroup)
-      groupUsers->insert(std::make_pair(usergroup->second, usergroup->first));
-
-    return userGroups;
+    boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > newUserGroups = backend->getFullUserGroupList(&userGroupTime);
+
+    if(newUserGroups) {
+      userGroups = newUserGroups;
+      userGroupException = Core::Exception();
+
+      groupUsers.reset(new std::multimap<unsigned long, unsigned long>);
+      for(std::multimap<unsigned long, unsigned long>::const_iterator usergroup = userGroups->begin(); usergroup != userGroups->end(); ++usergroup)
+        groupUsers->insert(std::make_pair(usergroup->second, usergroup->first));
+    }
+    else {
+      if(userGroups)
+        application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Using cached user-group table");
+      else
+        application->log(Core::LoggerBase::USER, Core::LoggerBase::DEBUG, "Error cached");
+    }
   }
   catch(Core::Exception e) {
+    userGroups.reset();
     userGroupException = e;
-    throw userGroupException;
   }
+
+  if((!timestamp) || timestamp->is_not_a_date_time() || (*timestamp < userTime)) {
+    if(timestamp)
+      *timestamp = userGroupTime;
+
+    if(userGroups)
+      return userGroups;
+    else
+      throw userGroupException;
+  }
+
+  return boost::shared_ptr<const std::multimap<unsigned long, unsigned long> >();
 }
 
 }
diff --git a/src/Common/UserCache.h b/src/Common/UserCache.h
index 548be2e..0fe26be 100644
--- a/src/Common/UserCache.h
+++ b/src/Common/UserCache.h
@@ -24,7 +24,7 @@
 
 #include <limits>
 
-#include <boost/thread/shared_mutex.hpp>
+#include <boost/thread/recursive_mutex.hpp>
 
 namespace Mad {
 namespace Common {
@@ -40,32 +40,35 @@ class UserCache : public UserBackend, private boost::noncopyable {
 
     boost::shared_ptr<UserBackend> backend;
 
-    boost::shared_mutex mutex;
+    boost::recursive_mutex mutex;
 
     boost::shared_ptr<const std::map<unsigned long, UserInfo> > users;
     boost::shared_ptr<std::map<std::string, unsigned long> > userNames;
     Core::Exception userException;
+    boost::posix_time::ptime userTime;
 
     boost::shared_ptr<const std::map<unsigned long, GroupInfo> > groups;
     boost::shared_ptr<std::map<std::string, unsigned long> > groupNames;
     Core::Exception groupException;
+    boost::posix_time::ptime groupTime;
 
     boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > userGroups;
     boost::shared_ptr<std::multimap<unsigned long, unsigned long> > groupUsers;
     Core::Exception userGroupException;
+    boost::posix_time::ptime userGroupTime;
 
   protected:
-    virtual boost::shared_ptr<const std::map<unsigned long, UserInfo> > getUserList() throw(Core::Exception);
-    virtual boost::shared_ptr<const UserInfo> getUserInfo(unsigned long uid) throw(Core::Exception);
-    virtual boost::shared_ptr<const UserInfo> getUserInfoByName(const std::string &name) throw(Core::Exception);
-    virtual boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::map<unsigned long, UserInfo> > getUserList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const UserInfo> getUserInfo(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const UserInfo> getUserInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
-    virtual boost::shared_ptr<const std::map<unsigned long, GroupInfo> > getGroupList() throw(Core::Exception);
-    virtual boost::shared_ptr<const GroupInfo> getGroupInfo(unsigned long gid) throw(Core::Exception);
-    virtual boost::shared_ptr<const GroupInfo> getGroupInfoByName(const std::string &name) throw(Core::Exception);
-    virtual boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::map<unsigned long, GroupInfo> > getGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const GroupInfo> getGroupInfo(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const GroupInfo> getGroupInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
-    virtual boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList() throw(Core::Exception);
+    virtual boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
     virtual void setPassword(unsigned long uid, const std::string &password) throw(Core::Exception) {
       backend->setPassword(uid, password);
@@ -75,7 +78,9 @@ class UserCache : public UserBackend, private boost::noncopyable {
       backend->addUser(userInfo);
     }
 
-    UserCache(Application *application0, boost::shared_ptr<UserBackend> backend0) : application(application0), backend(backend0) {}
+    UserCache(Application *application0, boost::shared_ptr<UserBackend> backend0) : application(application0), backend(backend0),
+    userTime(boost::posix_time::not_a_date_time), groupTime(boost::posix_time::not_a_date_time),
+    userGroupTime(boost::posix_time::not_a_date_time) {}
 };
 
 }
diff --git a/src/Common/UserManager.cpp b/src/Common/UserManager.cpp
index 1b20395..4031140 100644
--- a/src/Common/UserManager.cpp
+++ b/src/Common/UserManager.cpp
@@ -41,14 +41,14 @@ void UserManager::registerBackendCached(boost::shared_ptr<UserBackend> backend)
 }
 
 
-boost::shared_ptr<const std::map<unsigned long, UserInfo> > UserManager::getUserList() throw(Core::Exception) {
+boost::shared_ptr<const std::map<unsigned long, UserInfo> > UserManager::getUserList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::lock_guard<boost::shared_mutex> lock(mutex);
 
   for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
     try {
-      return backend->second->getUserList();
+      return backend->second->getUserList(timestamp);
     }
     catch(Core::Exception e2) {
       if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
@@ -59,14 +59,14 @@ boost::shared_ptr<const std::map<unsigned long, UserInfo> > UserManager::getUser
   throw e;
 }
 
-boost::shared_ptr<const UserInfo> UserManager::getUserInfo(unsigned long uid) throw(Core::Exception) {
+boost::shared_ptr<const UserInfo> UserManager::getUserInfo(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::lock_guard<boost::shared_mutex> lock(mutex);
 
   for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
     try {
-      return backend->second->getUserInfo(uid);
+      return backend->second->getUserInfo(uid, timestamp);
     }
     catch(Core::Exception e2) {
       if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
@@ -77,14 +77,14 @@ boost::shared_ptr<const UserInfo> UserManager::getUserInfo(unsigned long uid) th
   throw e;
 }
 
-boost::shared_ptr<const UserInfo> UserManager::getUserInfoByName(const std::string &name) throw(Core::Exception) {
+boost::shared_ptr<const UserInfo> UserManager::getUserInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::lock_guard<boost::shared_mutex> lock(mutex);
 
   for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
     try {
-      return backend->second->getUserInfoByName(name);
+      return backend->second->getUserInfoByName(name, timestamp);
     }
     catch(Core::Exception e2) {
       if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
@@ -95,14 +95,14 @@ boost::shared_ptr<const UserInfo> UserManager::getUserInfoByName(const std::stri
   throw e;
 }
 
-boost::shared_ptr<const std::set<unsigned long> > UserManager::getUserGroupList(unsigned long uid) throw(Core::Exception) {
+boost::shared_ptr<const std::set<unsigned long> > UserManager::getUserGroupList(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::lock_guard<boost::shared_mutex> lock(mutex);
 
   for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
     try {
-      return backend->second->getUserGroupList(uid);
+      return backend->second->getUserGroupList(uid, timestamp);
     }
     catch(Core::Exception e2) {
       if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
@@ -113,7 +113,7 @@ boost::shared_ptr<const std::set<unsigned long> > UserManager::getUserGroupList(
   throw e;
 }
 
-boost::shared_ptr<const std::map<unsigned long, GroupInfo> > UserManager::getGroupList() throw(Core::Exception) {
+boost::shared_ptr<const std::map<unsigned long, GroupInfo> > UserManager::getGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::shared_ptr<const std::map<unsigned long, GroupInfo> > ret;
@@ -123,7 +123,7 @@ boost::shared_ptr<const std::map<unsigned long, GroupInfo> > UserManager::getGro
 
     for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
       try {
-        return backend->second->getGroupList();
+        return backend->second->getGroupList(timestamp);
       }
       catch(Core::Exception e2) {
         if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
@@ -135,14 +135,14 @@ boost::shared_ptr<const std::map<unsigned long, GroupInfo> > UserManager::getGro
   throw e;
 }
 
-boost::shared_ptr<const GroupInfo> UserManager::getGroupInfo(unsigned long gid) throw(Core::Exception) {
+boost::shared_ptr<const GroupInfo> UserManager::getGroupInfo(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::lock_guard<boost::shared_mutex> lock(mutex);
 
   for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
     try {
-      return backend->second->getGroupInfo(gid);
+      return backend->second->getGroupInfo(gid, timestamp);
     }
     catch(Core::Exception e2) {
       if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
@@ -153,14 +153,14 @@ boost::shared_ptr<const GroupInfo> UserManager::getGroupInfo(unsigned long gid)
   throw e;
 }
 
-boost::shared_ptr<const GroupInfo> UserManager::getGroupInfoByName(const std::string &name) throw(Core::Exception) {
+boost::shared_ptr<const GroupInfo> UserManager::getGroupInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::lock_guard<boost::shared_mutex> lock(mutex);
 
   for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
     try {
-      return backend->second->getGroupInfoByName(name);
+      return backend->second->getGroupInfoByName(name, timestamp);
     }
     catch(Core::Exception e2) {
       if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
@@ -171,14 +171,14 @@ boost::shared_ptr<const GroupInfo> UserManager::getGroupInfoByName(const std::st
   throw e;
 }
 
-boost::shared_ptr<const std::set<unsigned long> > UserManager::getGroupUserList(unsigned long gid) throw(Core::Exception) {
+boost::shared_ptr<const std::set<unsigned long> > UserManager::getGroupUserList(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::lock_guard<boost::shared_mutex> lock(mutex);
 
   for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
     try {
-      return backend->second->getGroupUserList(gid);
+      return backend->second->getGroupUserList(gid, timestamp);
     }
     catch(Core::Exception e2) {
       if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
@@ -189,14 +189,14 @@ boost::shared_ptr<const std::set<unsigned long> > UserManager::getGroupUserList(
   throw e;
 }
 
-boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > UserManager::getFullUserGroupList() throw(Core::Exception) {
+boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > UserManager::getFullUserGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   Core::Exception e(Core::Exception::NOT_IMPLEMENTED);
 
   boost::lock_guard<boost::shared_mutex> lock(mutex);
 
   for(BackendMap::iterator backend = backends.begin(); backend != backends.end(); ++backend) {
     try {
-      return backend->second->getFullUserGroupList();
+      return backend->second->getFullUserGroupList(timestamp);
     }
     catch(Core::Exception e2) {
       if(e.getErrorCode() == Core::Exception::NOT_IMPLEMENTED && e2.getErrorCode() != Core::Exception::NOT_IMPLEMENTED)
diff --git a/src/Common/UserManager.h b/src/Common/UserManager.h
index c545f01..5877bac 100644
--- a/src/Common/UserManager.h
+++ b/src/Common/UserManager.h
@@ -69,17 +69,17 @@ class UserManager : private boost::noncopyable {
       backends.erase(backend);
     }
 
-    boost::shared_ptr<const std::map<unsigned long, UserInfo> > getUserList() throw(Core::Exception);
-    boost::shared_ptr<const UserInfo> getUserInfo(unsigned long uid) throw(Core::Exception);
-    boost::shared_ptr<const UserInfo> getUserInfoByName(const std::string &name) throw(Core::Exception);
-    boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid) throw(Core::Exception);
+    boost::shared_ptr<const std::map<unsigned long, UserInfo> > getUserList(boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
+    boost::shared_ptr<const UserInfo> getUserInfo(unsigned long uid, boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
+    boost::shared_ptr<const UserInfo> getUserInfoByName(const std::string &name, boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
+    boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid, boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
 
-    boost::shared_ptr<const std::map<unsigned long, GroupInfo> > getGroupList() throw(Core::Exception);
-    boost::shared_ptr<const GroupInfo> getGroupInfo(unsigned long gid) throw(Core::Exception);
-    boost::shared_ptr<const GroupInfo> getGroupInfoByName(const std::string &name) throw(Core::Exception);
-    boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid) throw(Core::Exception);
+    boost::shared_ptr<const std::map<unsigned long, GroupInfo> > getGroupList(boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
+    boost::shared_ptr<const GroupInfo> getGroupInfo(unsigned long gid, boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
+    boost::shared_ptr<const GroupInfo> getGroupInfoByName(const std::string &name, boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
+    boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid, boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
 
-    boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList() throw(Core::Exception);
+    boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList(boost::posix_time::ptime *timestamp = 0) throw(Core::Exception);
 
     void setPassword(unsigned long uid, const std::string &password) throw(Core::Exception);
 
diff --git a/src/Server/RequestHandlers/UserRequestHandlerGroup.cpp b/src/Server/RequestHandlers/UserRequestHandlerGroup.cpp
index d579480..292e887 100644
--- a/src/Server/RequestHandlers/UserRequestHandlerGroup.cpp
+++ b/src/Server/RequestHandlers/UserRequestHandlerGroup.cpp
@@ -17,99 +17,196 @@
  * with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <config.h>
+
 #include "UserRequestHandlerGroup.h"
 #include "../Application.h"
+
 #include <Common/UserManager.h>
 
+#include <boost/date_time/posix_time/posix_time.hpp>
+
 namespace Mad {
 namespace Server {
 namespace RequestHandlers {
 
-void UserRequestHandlerGroup::handleUserListRequest(boost::shared_ptr<const Common::XmlPacket> packet _UNUSED_PARAMETER_, Common::XmlPacket *ret,
+void UserRequestHandlerGroup::handleUserListRequest(boost::shared_ptr<const Common::XmlPacket> packet, Common::XmlPacket *ret,
     Common::Connection *connection _UNUSED_PARAMETER_) {
-  boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> > info = application->getUserManager()->getUserList();
+  boost::posix_time::ptime timestamp(boost::posix_time::not_a_date_time);
+
+  const std::string &timestr = packet->get<const std::string&>("timestamp");
+  if(!timestr.empty()) {
+    try {
+      timestamp = boost::posix_time::from_iso_string(timestr);
+    }
+    catch(...) {}
+  }
+
+  boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> > users = application->getUserManager()->getUserList(&timestamp);
 
   ret->setType("OK");
-  Common::XmlPacket::List *list = ret->createList("users");
 
-  for(std::map<unsigned long, Common::UserInfo>::const_iterator user = info->begin(); user != info->end(); ++user) {
-    Common::XmlPacket::List::iterator entry = list->addEntry();
+  if(!timestamp.is_not_a_date_time())
+    ret->set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
+  if(users) {
+    Common::XmlPacket::List *list = ret->createList("users");
+
+    for(std::map<unsigned long, Common::UserInfo>::const_iterator user = users->begin(); user != users->end(); ++user) {
+      Common::XmlPacket::List::iterator entry = list->addEntry();
 
-    entry->set("uid", user->second.getUid());
-    entry->set("gid", user->second.getGid());
-    entry->set("username", user->second.getUsername());
-    entry->set("fullName", user->second.getFullName());
+      entry->set("uid", user->second.getUid());
+      entry->set("gid", user->second.getGid());
+      entry->set("username", user->second.getUsername());
+      entry->set("fullName", user->second.getFullName());
+    }
   }
 }
 
 void UserRequestHandlerGroup::handleUserInfoRequest(boost::shared_ptr<const Common::XmlPacket> packet, Common::XmlPacket *ret,
     Common::Connection *connection _UNUSED_PARAMETER_) {
+  boost::posix_time::ptime timestamp(boost::posix_time::not_a_date_time);
+
+  const std::string &timestr = packet->get<const std::string&>("timestamp");
+  if(!timestr.empty()) {
+    try {
+      timestamp = boost::posix_time::from_iso_string(timestr);
+    }
+    catch(...) {}
+  }
+
   boost::shared_ptr<const Common::UserInfo> info;
 
   unsigned long uid = packet->get<unsigned long>("uid");
   if(uid)
-    info = application->getUserManager()->getUserInfo(uid);
+    info = application->getUserManager()->getUserInfo(uid, &timestamp);
   else
-    info = application->getUserManager()->getUserInfoByName(packet->get<const std::string&>("name"));
+    info = application->getUserManager()->getUserInfoByName(packet->get<const std::string&>("name"), &timestamp);
 
   ret->setType("OK");
 
-  ret->set("uid", info->getUid());
-  ret->set("gid", info->getGid());
-  ret->set("username", info->getUsername());
-  ret->set("fullName", info->getFullName());
+  if(!timestamp.is_not_a_date_time())
+    ret->set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
+  if(info) {
+    ret->set("uid", info->getUid());
+    ret->set("gid", info->getGid());
+    ret->set("username", info->getUsername());
+    ret->set("fullName", info->getFullName());
+  }
 }
 
 void UserRequestHandlerGroup::handleUserGroupListRequest(boost::shared_ptr<const Common::XmlPacket> packet, Common::XmlPacket *ret,
     Common::Connection *connection _UNUSED_PARAMETER_) {
-  boost::shared_ptr<const std::set<unsigned long> > groups = application->getUserManager()->getUserGroupList(packet->get<unsigned long>("uid"));
+  boost::posix_time::ptime timestamp(boost::posix_time::not_a_date_time);
+
+  const std::string &timestr = packet->get<const std::string&>("timestamp");
+  if(!timestr.empty()) {
+    try {
+      timestamp = boost::posix_time::from_iso_string(timestr);
+    }
+    catch(...) {}
+  }
+
+  boost::shared_ptr<const std::set<unsigned long> > groups = application->getUserManager()->getUserGroupList(packet->get<unsigned long>("uid"), &timestamp);
 
   ret->setType("OK");
-  Common::XmlPacket::List *list = ret->createList("groups");
 
-  for(std::set<unsigned long>::const_iterator group = groups->begin(); group != groups->end(); ++group) {
-    Common::XmlPacket::List::iterator entry = list->addEntry();
+  if(!timestamp.is_not_a_date_time())
+    ret->set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
+  if(groups) {
+    Common::XmlPacket::List *list = ret->createList("groups");
+
+    for(std::set<unsigned long>::const_iterator group = groups->begin(); group != groups->end(); ++group) {
+      Common::XmlPacket::List::iterator entry = list->addEntry();
 
-    entry->set("gid", *group);
+      entry->set("gid", *group);
+    }
   }
 }
 
-void UserRequestHandlerGroup::handleGroupListRequest(boost::shared_ptr<const Common::XmlPacket> packet _UNUSED_PARAMETER_, Common::XmlPacket *ret,
+void UserRequestHandlerGroup::handleGroupListRequest(boost::shared_ptr<const Common::XmlPacket> packet, Common::XmlPacket *ret,
     Common::Connection *connection _UNUSED_PARAMETER_) {
-  boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> > info = application->getUserManager()->getGroupList();
+  boost::posix_time::ptime timestamp(boost::posix_time::not_a_date_time);
+
+  const std::string &timestr = packet->get<const std::string&>("timestamp");
+  if(!timestr.empty()) {
+    try {
+      timestamp = boost::posix_time::from_iso_string(timestr);
+    }
+    catch(...) {}
+  }
+
+  boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> > groups = application->getUserManager()->getGroupList(&timestamp);
 
   ret->setType("OK");
-  Common::XmlPacket::List *list = ret->createList("groups");
 
-  for(std::map<unsigned long, Common::GroupInfo>::const_iterator group = info->begin(); group != info->end(); ++group) {
-    Common::XmlPacket::List::iterator entry = list->addEntry();
+  if(!timestamp.is_not_a_date_time())
+    ret->set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
+  if(groups) {
+    Common::XmlPacket::List *list = ret->createList("groups");
+
+    for(std::map<unsigned long, Common::GroupInfo>::const_iterator group = groups->begin(); group != groups->end(); ++group) {
+      Common::XmlPacket::List::iterator entry = list->addEntry();
 
-    entry->set("gid", group->second.getGid());
-    entry->set("name", group->second.getName());
+      entry->set("gid", group->second.getGid());
+      entry->set("name", group->second.getName());
+    }
   }
 }
 
 void UserRequestHandlerGroup::handleGroupInfoRequest(boost::shared_ptr<const Common::XmlPacket> packet, Common::XmlPacket *ret,
     Common::Connection *connection _UNUSED_PARAMETER_) {
+  boost::posix_time::ptime timestamp(boost::posix_time::not_a_date_time);
+
+  const std::string &timestr = packet->get<const std::string&>("timestamp");
+  if(!timestr.empty()) {
+    try {
+      timestamp = boost::posix_time::from_iso_string(timestr);
+    }
+    catch(...) {}
+  }
+
   boost::shared_ptr<const Common::GroupInfo> info;
 
   unsigned long gid = packet->get<unsigned long>("gid");
   if(gid)
-    info = application->getUserManager()->getGroupInfo(gid);
+    info = application->getUserManager()->getGroupInfo(gid, &timestamp);
   else
-    info = application->getUserManager()->getGroupInfoByName(packet->get<const std::string&>("name"));
+    info = application->getUserManager()->getGroupInfoByName(packet->get<const std::string&>("name"), &timestamp);
 
   ret->setType("OK");
 
-  ret->set("gid", info->getGid());
-  ret->set("name", info->getName());
+  if(!timestamp.is_not_a_date_time())
+    ret->set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
+  if(info) {
+    ret->set("gid", info->getGid());
+    ret->set("name", info->getName());
+  }
 }
 
 void UserRequestHandlerGroup::handleGroupUserListRequest(boost::shared_ptr<const Common::XmlPacket> packet, Common::XmlPacket *ret,
     Common::Connection *connection _UNUSED_PARAMETER_) {
-  boost::shared_ptr<const std::set<unsigned long> > users = application->getUserManager()->getGroupUserList(packet->get<unsigned long>("gid"));
+  boost::posix_time::ptime timestamp(boost::posix_time::not_a_date_time);
+
+  const std::string &timestr = packet->get<const std::string&>("timestamp");
+  if(!timestr.empty()) {
+    try {
+      timestamp = boost::posix_time::from_iso_string(timestr);
+    }
+    catch(...) {}
+  }
+
+  boost::shared_ptr<const std::set<unsigned long> > users = application->getUserManager()->getGroupUserList(packet->get<unsigned long>("gid"), &timestamp);
 
   ret->setType("OK");
+
+  if(!timestamp.is_not_a_date_time())
+    ret->set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
   Common::XmlPacket::List *list = ret->createList("users");
 
   for(std::set<unsigned long>::const_iterator user = users->begin(); user != users->end(); ++user) {
@@ -119,18 +216,34 @@ void UserRequestHandlerGroup::handleGroupUserListRequest(boost::shared_ptr<const
   }
 }
 
-void UserRequestHandlerGroup::handleFullUserGroupListRequest(boost::shared_ptr<const Common::XmlPacket> packet _UNUSED_PARAMETER_, Common::XmlPacket *ret,
+void UserRequestHandlerGroup::handleFullUserGroupListRequest(boost::shared_ptr<const Common::XmlPacket> packet, Common::XmlPacket *ret,
     Common::Connection *connection _UNUSED_PARAMETER_) {
-  boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > userGroups = application->getUserManager()->getFullUserGroupList();
+  boost::posix_time::ptime timestamp(boost::posix_time::not_a_date_time);
+
+  const std::string &timestr = packet->get<const std::string&>("timestamp");
+  if(!timestr.empty()) {
+    try {
+      timestamp = boost::posix_time::from_iso_string(timestr);
+    }
+    catch(...) {}
+  }
+
+  boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > userGroups = application->getUserManager()->getFullUserGroupList(&timestamp);
 
   ret->setType("OK");
-  Common::XmlPacket::List *list = ret->createList("userGroupList");
 
-  for(std::map<unsigned long, unsigned long>::const_iterator userGroup = userGroups->begin(); userGroup != userGroups->end(); ++userGroup) {
-    Common::XmlPacket::List::iterator entry = list->addEntry();
+  if(!timestamp.is_not_a_date_time())
+    ret->set("timestamp", boost::posix_time::to_iso_string(timestamp));
+
+  if(userGroups) {
+    Common::XmlPacket::List *list = ret->createList("userGroupList");
+
+    for(std::map<unsigned long, unsigned long>::const_iterator userGroup = userGroups->begin(); userGroup != userGroups->end(); ++userGroup) {
+      Common::XmlPacket::List::iterator entry = list->addEntry();
 
-    entry->set("uid", userGroup->first);
-    entry->set("gid", userGroup->second);
+      entry->set("uid", userGroup->first);
+      entry->set("gid", userGroup->second);
+    }
   }
 }
 
diff --git a/src/modules/UserBackendMysql/UserBackendMysql.cpp b/src/modules/UserBackendMysql/UserBackendMysql.cpp
index 6d64a51..82258e8 100644
--- a/src/modules/UserBackendMysql/UserBackendMysql.cpp
+++ b/src/modules/UserBackendMysql/UserBackendMysql.cpp
@@ -134,11 +134,18 @@ void UserBackendMysql::configFinished() {
 }
 
 
-boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> > UserBackendMysql::getUserList() throw(Core::Exception) {
+boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> > UserBackendMysql::getUserList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> >();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
@@ -164,11 +171,18 @@ boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> > UserBackendM
   return users;
 }
 
-boost::shared_ptr<const Common::UserInfo> UserBackendMysql::getUserInfo(unsigned long uid) throw(Core::Exception) {
+boost::shared_ptr<const Common::UserInfo> UserBackendMysql::getUserInfo(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const Common::UserInfo>();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
@@ -205,11 +219,18 @@ boost::shared_ptr<const Common::UserInfo> UserBackendMysql::getUserInfo(unsigned
   throw Core::Exception(Core::Exception::NOT_FOUND);
 }
 
-boost::shared_ptr<const Common::UserInfo> UserBackendMysql::getUserInfoByName(const std::string &name) throw(Core::Exception) {
+boost::shared_ptr<const Common::UserInfo> UserBackendMysql::getUserInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const Common::UserInfo>();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
@@ -243,11 +264,18 @@ boost::shared_ptr<const Common::UserInfo> UserBackendMysql::getUserInfoByName(co
   throw Core::Exception(Core::Exception::NOT_FOUND);
 }
 
-boost::shared_ptr<const std::set<unsigned long> > UserBackendMysql::getUserGroupList(unsigned long uid) throw(Core::Exception) {
+boost::shared_ptr<const std::set<unsigned long> > UserBackendMysql::getUserGroupList(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const std::set<unsigned long> >();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
@@ -275,11 +303,18 @@ boost::shared_ptr<const std::set<unsigned long> > UserBackendMysql::getUserGroup
 }
 
 
-boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> > UserBackendMysql::getGroupList() throw(Core::Exception) {
+boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> > UserBackendMysql::getGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> >();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
@@ -302,11 +337,18 @@ boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> > UserBackend
   return groups;
 }
 
-boost::shared_ptr<const Common::GroupInfo> UserBackendMysql::getGroupInfo(unsigned long gid) throw(Core::Exception) {
+boost::shared_ptr<const Common::GroupInfo> UserBackendMysql::getGroupInfo(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const Common::GroupInfo>();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
@@ -335,11 +377,18 @@ boost::shared_ptr<const Common::GroupInfo> UserBackendMysql::getGroupInfo(unsign
   throw Core::Exception(Core::Exception::NOT_FOUND);
 }
 
-boost::shared_ptr<const Common::GroupInfo> UserBackendMysql::getGroupInfoByName(const std::string &name) throw(Core::Exception) {
+boost::shared_ptr<const Common::GroupInfo> UserBackendMysql::getGroupInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const Common::GroupInfo>();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
@@ -365,11 +414,18 @@ boost::shared_ptr<const Common::GroupInfo> UserBackendMysql::getGroupInfoByName(
   throw Core::Exception(Core::Exception::NOT_FOUND);
 }
 
-boost::shared_ptr<const std::set<unsigned long> > UserBackendMysql::getGroupUserList(unsigned long gid) throw(Core::Exception) {
+boost::shared_ptr<const std::set<unsigned long> > UserBackendMysql::getGroupUserList(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const std::set<unsigned long> >();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
@@ -396,11 +452,18 @@ boost::shared_ptr<const std::set<unsigned long> > UserBackendMysql::getGroupUser
   return users;
 }
 
-boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > UserBackendMysql::getFullUserGroupList() throw(Core::Exception) {
+boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > UserBackendMysql::getFullUserGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception) {
   application->getThreadManager()->detach();
 
   boost::unique_lock<boost::mutex> lock(mutex);
 
+  if(timestamp) {
+    if(timestamp->is_not_a_date_time() || *timestamp < lastUpdate)
+      *timestamp = lastUpdate;
+    else
+      return boost::shared_ptr<const std::multimap<unsigned long, unsigned long> >();
+  }
+
   if(!mysql || mysql_ping(mysql))
     throw Core::Exception(Core::Exception::NOT_AVAILABLE);
 
diff --git a/src/modules/UserBackendMysql/UserBackendMysql.h b/src/modules/UserBackendMysql/UserBackendMysql.h
index eadbf3b..52a134a 100644
--- a/src/modules/UserBackendMysql/UserBackendMysql.h
+++ b/src/modules/UserBackendMysql/UserBackendMysql.h
@@ -49,26 +49,28 @@ class UserBackendMysql : public Common::UserBackend, private Core::Configurable
 
     MYSQL *mysql;
 
+    boost::posix_time::ptime lastUpdate;
+
     boost::mutex mutex;
 
   protected:
     virtual bool handleConfigEntry(const Core::ConfigEntry &entry, bool);
     virtual void configFinished();
 
-    virtual boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> > getUserList() throw(Core::Exception);
-    virtual boost::shared_ptr<const Common::UserInfo> getUserInfo(unsigned long uid) throw(Core::Exception);
-    virtual boost::shared_ptr<const Common::UserInfo> getUserInfoByName(const std::string &name) throw(Core::Exception);
-    virtual boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::map<unsigned long, Common::UserInfo> > getUserList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const Common::UserInfo> getUserInfo(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const Common::UserInfo> getUserInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::set<unsigned long> > getUserGroupList(unsigned long uid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
-    virtual boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> > getGroupList() throw(Core::Exception);
-    virtual boost::shared_ptr<const Common::GroupInfo> getGroupInfo(unsigned long gid) throw(Core::Exception);
-    virtual boost::shared_ptr<const Common::GroupInfo> getGroupInfoByName(const std::string &name) throw(Core::Exception);
-    virtual boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::map<unsigned long, Common::GroupInfo> > getGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const Common::GroupInfo> getGroupInfo(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const Common::GroupInfo> getGroupInfoByName(const std::string &name, boost::posix_time::ptime *timestamp) throw(Core::Exception);
+    virtual boost::shared_ptr<const std::set<unsigned long> > getGroupUserList(unsigned long gid, boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
-    virtual boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList() throw(Core::Exception);
+    virtual boost::shared_ptr<const std::multimap<unsigned long, unsigned long> > getFullUserGroupList(boost::posix_time::ptime *timestamp) throw(Core::Exception);
 
   public:
-    UserBackendMysql(Common::Application *application0) : application(application0), port(0), mysql(0) {
+    UserBackendMysql(Common::Application *application0) : application(application0), port(0), mysql(0), lastUpdate(boost::posix_time::microsec_clock::universal_time()) {
       application->getConfigManager()->registerConfigurable(this);
     }