diff --git a/python/mine/ri_cmd.py b/python/mine/ri_cmd.py
index bd24bae..13844f7 100644
--- a/python/mine/ri_cmd.py
+++ b/python/mine/ri_cmd.py
@@ -13,17 +13,18 @@ import sys
 def quit():
     ''' correspond to quit button '''
     # maybe a quit in current widget, so call widget.hide()
-    if ri_widget.Widget.current_widget:
-        ri_widget.Widget.current_widget.hide()
+    # get current widget, call its quit()
+    q, t = ri_seq.Sequence.current()
+    ri_widget.Widget.dict[t].hide()
     display.quit()
     ri_data.to_xml()
 
 def previous():
     ''' correspond to previous button '''
+    q, t = ri_seq.Sequence.current()
     wid_name = ri_seq.previous()
     if wid_name is not None:
-        if ri_widget.Widget.current_widget:
-            ri_widget.Widget.current_widget.hide()
+        ri_widget.Widget.dict[t].hide()
 
         ri_widget.Widget.dict[wid_name].show()
     else:
@@ -31,10 +32,10 @@ def previous():
 
 def next():
     ''' correspond to next button '''
+    q, t = ri_seq.Sequence.current()
     wid_name = ri_seq.next()
     if wid_name is not None:
-        if ri_widget.Widget.current_widget:
-            ri_widget.Widget.current_widget.hide()
+        ri_widget.Widget.dict[t].hide()
 
         ri_widget.Widget.dict[wid_name].show()
     else:
diff --git a/python/mine/ri_seq.py b/python/mine/ri_seq.py
index cfe0ca5..3b63739 100644
--- a/python/mine/ri_seq.py
+++ b/python/mine/ri_seq.py
@@ -1,48 +1,39 @@
 #!/usr/bin/python
 
-current_sequence=""
-previous_sequences=[]
-dict={}
-
 class Sequence:
     ''' implement sequence in interface xml'''
+    dict={}
+
     def __init__(self, xml_node):
         self.steps = [ s.attributes["name"].value for s in xml_node.childNodes
                  if s.nodeType == s.ELEMENT_NODE and s.nodeName == "widget" ]
         self.current_step = 0
 
-    def set_step(self, st):
+    def set_current_step(self, st):
         ''' set current step based on input step name'''
         self.current_step = self.steps.index(st)
 
+    @staticmethod
+    def set_current_sequence(name):
+        Sequence.current_sequence = Sequence.dict[name]
+
+    @staticmethod
+    def current():
+        return (Sequence.current_sequence, Sequence.current_sequence.steps[Sequence.current_sequence.current_step])
+        
+
 def construct(xml_root):
     ''' construct Sequence's static members'''
-    global current_sequence
-    current_sequence = xml_root.attributes["sequence"].value
     for s in xml_root.childNodes:
         if s.nodeType == s.ELEMENT_NODE and s.nodeName == "sequence":
-            dict[s.attributes["name"].value] = Sequence(s)
+            Sequence.dict[s.attributes["name"].value] = Sequence(s)
 
 def previous():
-    global current_sequence
-    cur_seq = dict[current_sequence]
-    if cur_seq.current_step:
-        cur_seq.current_step -= 1
-        return cur_seq.steps[cur_seq.current_step]
-    # current sequence already in first step
-    elif previous_sequences:
-        current_sequence = previous_sequences.pop()
-        cur_seq = dict[current_sequence]
-        return cur_seq.steps[cur_seq.current_step]
+    if Sequence.current_sequence.current_step:
+        Sequence.current_sequence.current_step -= 1
+        return Sequence.current_sequence.steps[Sequence.current_sequence.current_step]
 
 def next():
-    global current_sequence
-    cur_seq = dict[current_sequence]
-    if cur_seq.current_step < len(cur_seq.steps)-1:
-        cur_seq.current_step += 1
-        return cur_seq.steps[cur_seq.current_step]
-    # current sequence already in last step
-    elif previous_sequences:
-        current_sequence = previous_sequences.pop()
-        cur_seq = dict[current_sequence]
-        return cur_seq.steps[cur_seq.current_step]
+    if Sequence.current_sequence.current_step < len(Sequence.current_sequence.steps)-1:
+        Sequence.current_sequence.current_step += 1
+        return Sequence.current_sequence.steps[Sequence.current_sequence.current_step]
diff --git a/python/mine/test.py b/python/mine/test.py
index ad55cf1..4baf9f2 100644
--- a/python/mine/test.py
+++ b/python/mine/test.py
@@ -45,7 +45,8 @@ base_widget_name = xmldoc.firstChild.attributes["base_widget"].value
 ri_widget.init_display(base_widget_name)
 
 main_sequence_name = xmldoc.firstChild.attributes["sequence"].value
-main_sequence = ri_seq.dict[main_sequence_name]
+ri_seq.Sequence.set_current_sequence(main_sequence_name)
+main_sequence = ri_seq.Sequence.dict[main_sequence_name]
 
 if begin_step is None:
     begin_step = main_sequence.steps[0]