diff --git a/tracking/README.txt b/tracking/README.txt
new file mode 100644
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--- /dev/null
+++ b/tracking/README.txt
@@ -0,0 +1,39 @@
+====================================
+User tracking in the loops framework
+====================================
+
+  ($Id$)
+
+  >>> from cybertools.tracking.btree import TrackingStorage
+
+  >>> tracks = TrackingStorage()
+  >>> runId = tracks.startRun('a001')
+  >>> tracks.saveUserTrack('a001', runId, 'u1', {'somekey': 'somevalue'})
+  '0000001'
+  >>> t1 = tracks.getUserTrack('a001', runId, 'u1')
+  >>> t1.data
+  {'somekey': 'somevalue'}
+  >>> tracks.getUserNames('a001')
+  ['u1']
+  >>> tracks.getUserNames('a002')
+  []
+  >>> [str(id) for id in tracks.getTaskIds()]
+  ['a001']
+
+  >>> tracks.query(taskId='a001')
+  [<Track ['a001', 1, 'u1', '...-...-... ...:...']: {'somekey': 'somevalue'}>]
+
+  >>> tracks.saveUserTrack('a002', 0, 'u1', {'somekey': 'anothervalue'})
+  '0000002'
+  >>> result = tracks.query(userName='u1')
+  >>> len(result)
+  2
+
+The tracks of a tracking store may be reindexed:
+
+  >>> tracks.reindexTracks()
+
+
+Fin de partie
+=============
+
diff --git a/tracking/__init__.py b/tracking/__init__.py
new file mode 100644
index 0000000..4bc90fb
--- /dev/null
+++ b/tracking/__init__.py
@@ -0,0 +1,4 @@
+"""
+$Id$
+"""
+
diff --git a/tracking/btree.py b/tracking/btree.py
new file mode 100644
index 0000000..68992af
--- /dev/null
+++ b/tracking/btree.py
@@ -0,0 +1,148 @@
+#
+#  Copyright (c) 2005 Helmut Merz helmutm@cy55.de
+#
+#  This program 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 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program 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 this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+
+"""
+BTree-based implementation of user tracking.
+
+$Id$
+"""
+
+import time
+
+from zope.interface import implements
+from zope.app.container.btree import BTreeContainer
+from zope.index.field import FieldIndex
+
+from persistent import Persistent
+from BTrees import OOBTree
+from BTrees.IFBTree import intersection
+
+from interfaces import ITrackingStorage, ITrack
+
+
+class TrackingStorage(BTreeContainer):
+
+    implements(ITrackingStorage)
+
+    trackNum = runId = 0
+
+    indexAttributes = ('taskId', 'runId', 'userName', 'timeStamp')
+
+    def __init__(self, *args, **kw):
+        super(TrackingStorage, self).__init__(*args, **kw)
+        self.indexes = OOBTree.OOBTree()
+        for idx in self.indexAttributes:
+            self.indexes[idx] = FieldIndex()
+        self.currentRuns = OOBTree.OOBTree()
+        self.taskUsers = OOBTree.OOBTree()
+
+    def idFromNum(self, num):
+        return '%07i' % (num)
+
+    def startRun(self, taskId):
+        self.runId += 1
+        self.currentRuns[taskId] = self.runId
+        return self.runId
+
+    def stopRun(self, taskId):
+        if taskId in self.currentRuns:
+            del self.currentRuns[taskId]
+
+    def saveUserTrack(self, taskId, runId, userName, data):
+        if not runId:
+            runId = self.currentRuns.get(taskId) or self.startRun(taskId)
+        self.trackNum += 1
+        trackNum = self.trackNum
+        trackId = self.idFromNum(trackNum)
+        timeStamp = int(time.time())
+        track = Track(taskId, runId, userName, timeStamp, data)
+        self[trackId] = track
+        self.indexTrack(trackNum, track)
+        return trackId
+
+    def indexTrack(self, trackNum, track):
+        md = track.metadata
+        for attr in self.indexAttributes:
+            self.indexes[attr].index_doc(trackNum, md[attr])
+        taskId = md['taskId']
+        userName = md['userName']
+        if taskId not in self.taskUsers:
+            self.taskUsers[taskId] = OOBTree.OOTreeSet()
+        self.taskUsers[taskId].update([userName])
+
+    def reindexTracks(self):
+        for trackId in self:
+            trackNum = int(trackId)
+            self.indexTrack(trackNum, self[trackId])
+
+    def getUserTrack(self, taskId, runId, userName):
+        if not runId:
+            runId = self.currentRuns.get(taskId)
+        tracks = self.query(taskId=taskId, runId=runId, userName=userName)
+        return tracks and tracks[0] or None
+
+    def query(self, **kw):
+        result = None
+        for idx in kw:
+            value = kw[idx]
+            if idx in self.indexAttributes:
+                result = self.intersect(result, self.indexes[idx].apply((value, value)))
+            elif idx == 'timeFrom':
+                result = self.intersect(result,
+                                        self.indexes['timeStamp'].apply((value, None)))
+            elif idx == 'timeTo':
+                result = self.intersect(result,
+                                        self.indexes['timeStamp'].apply((None, value)))
+        return result and [self[self.idFromNum(r)] for r in result] or set()
+
+    def intersect(self, r1, r2):
+        return r1 and intersection(r1, r2) or r2
+
+    def getUserNames(self, taskId):
+        return sorted(self.taskUsers.get(taskId, []))
+
+    def getTaskIds(self):
+        return self.taskUsers.keys()
+
+
+class Track(Persistent):
+
+    implements(ITrack)
+
+    metadata_attributes = ('taskId', 'runId', 'userName', 'timeStamp')
+
+    @property
+    def metadata(self):
+        return dict((attr, getattr(self, attr)) for attr in self.metadata_attributes)
+
+    def __init__(self, taskId, runId, userName, timeStamp, data={}):
+        self.taskId = taskId
+        self.runId = runId
+        self.userName = userName
+        self.timeStamp = timeStamp
+        self.data = data
+
+    def __repr__(self):
+        md = self.metadata
+        md['timeStamp'] = timeStamp2ISO(md['timeStamp'])
+        return '<Track %s: %s>' % (`[md[a] for a in self.metadata_attributes]`,
+                                     `self.data`)
+
+def timeStamp2ISO(ts):
+    return time.strftime('%Y-%m-%d %H:%M', time.gmtime(ts))
+
diff --git a/tracking/interfaces.py b/tracking/interfaces.py
new file mode 100644
index 0000000..604c20f
--- /dev/null
+++ b/tracking/interfaces.py
@@ -0,0 +1,78 @@
+#
+#  Copyright (c) 2005 Helmut Merz helmutm@cy55.de
+#
+#  This program 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 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program 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 this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+
+"""
+loops tracking interface definitions.
+
+$Id$
+"""
+
+from zope.interface import Interface, Attribute
+from zope import schema
+
+
+# user interaction tracking
+
+class ITrack(Interface):
+    """ Result data from the interactions of a user with an task.
+    """
+
+    data = Attribute('The data for this track, typically a mapping')
+    metadata = Attribute('A mapping with the track\'s metadata')
+
+
+class ITrackingStorage(Interface):
+    """ A utility for storing user tracks.
+    """
+
+    def startRun(taskId):
+        """ Creates a new run for the task given and return its id.
+        """
+
+    def stopRun(taskId):
+        """ Remove the current run entry for the task given.
+        """
+
+    def saveUserTrack(taskId, runId, userName, data):
+        """ Save the data given (typically a mapping object) to the user track
+            corresponding to the user name, task id, and run id given.
+        """
+
+    def query(**criteria):
+        """ Search for tracks. Possible criteria are: taskId, runId,
+            userName, timeFrom, timeTo.
+        """
+
+    def getUserTrack(taskId, runId, userName):
+        """ Return the user track data corresponding to the user name and
+            task id given. If no run id is given use the current one.
+        """
+
+    def getUserNames(taskId):
+        """ Return all user names (user ids) that have tracks for the
+            task given.
+        """
+
+    def getTaskIds():
+        """ Return all ids of the tasks for which there are any tracks.
+        """
+
+    def reindexTracks():
+        """ Reindexes all tracks - in case of trouble...
+        """
+
diff --git a/tracking/tests.py b/tracking/tests.py
new file mode 100755
index 0000000..d0a6bb1
--- /dev/null
+++ b/tracking/tests.py
@@ -0,0 +1,22 @@
+# $Id$
+
+import unittest, doctest
+from zope.testing.doctestunit import DocFileSuite
+
+
+class Test(unittest.TestCase):
+    "Basic tests for the loops.track package."
+
+    def testBasics(self):
+        pass
+
+
+def test_suite():
+    flags = doctest.NORMALIZE_WHITESPACE | doctest.ELLIPSIS
+    return unittest.TestSuite((
+                unittest.makeSuite(Test),
+                DocFileSuite('README.txt', optionflags=flags),
+            ))
+
+if __name__ == '__main__':
+    unittest.main(defaultTest='test_suite')