diff --git a/src/service/dialog_state_monitor.py b/src/service/dialog_state_monitor.py
index c4728d0..b01e808 100644
--- a/src/service/dialog_state_monitor.py
+++ b/src/service/dialog_state_monitor.py
@@ -1,5 +1,4 @@
-from model.frame import Frame
-from convlab.dst.dst import DST
+from src.model.frame import Frame
 import copy
 
 
@@ -8,14 +7,9 @@ def normalize(value):
     return ' '.join(value.split())
 
 
-class DialogStateMonitor(DST):
-    domain = 'restaurant'
-
+class DialogStateMonitor:
     def __init__(self):
-        DST.__init__(self)
-        self.__initial_state = dict(user_action=[],
-                                    system_action=[],
-                                    belief_state={
+        self.__initial_state = dict(belief_state={
                                         'order': [],
                                         'address': {},
                                         'order-complete': False,
@@ -25,13 +19,11 @@ class DialogStateMonitor(DST):
                                         'time': {},
                                         'name': {},
                                     },
-                                    booked={},
-                                    request_state={},
-                                    terminated=False,
                                     history=[])
         self.state = copy.deepcopy(self.__initial_state)
 
     def update(self, frame: Frame):
+        self.state['history'].append(frame)
         if frame.source != 'user':
             return
         if frame.act == 'inform/order':
diff --git a/src/test/dialog_state_monitor.py b/src/test/dialog_state_monitor.py
index 922b26e..8614126 100644
--- a/src/test/dialog_state_monitor.py
+++ b/src/test/dialog_state_monitor.py
@@ -4,15 +4,22 @@ from src.model.slot import Slot
 
 dst = DialogStateMonitor()
 
-dst.update(Frame('user', 'inform/order', [Slot('pizza', 'margaritta'), Slot('sauce', 'ketchup')]))
-dst.update(Frame('user', 'inform/order', [Slot('pizza', 'carbonara')]))
-dst.update(Frame('user', 'inform/order-complete', []))
+frame1 = Frame('user', 'inform/order', [Slot('pizza', 'margaritta'), Slot('sauce', 'ketchup')])
+frame2 = Frame('user', 'inform/order', [Slot('pizza', 'carbonara')])
+frame3 = Frame('user', 'inform/order-complete', [])
+dst.update(frame1)
+dst.update(frame2)
+dst.update(frame3)
 
 assert dst.state['belief_state']['order'][0]['pizza'] == 'margaritta'
 assert dst.state['belief_state']['order'][0]['sauce'] == 'ketchup'
-assert dst.state['belief_state']['order-complete'] == True
+assert dst.state['belief_state']['order-complete'] is True
+assert dst.state['history'][0] == frame1
+assert dst.state['history'][1] == frame2
+assert dst.state['history'][2] == frame3
 
 dst.reset()
 
 assert dst.state['belief_state']['order'] == []
-assert dst.state['belief_state']['order-complete'] == False
+assert dst.state['belief_state']['order-complete'] is False
+assert len(dst.state['history']) == 0