diff -r 058bb3dc685f -r 0b59724cb3f2 cubicweb/transaction.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cubicweb/transaction.py	Sat Jan 16 13:48:51 2016 +0100
@@ -0,0 +1,127 @@
+# copyright 2003-2014 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This file is part of CubicWeb.
+#
+# CubicWeb is free software: you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# CubicWeb 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 Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License along
+# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
+""" undoable transaction objects. """
+__docformat__ = "restructuredtext en"
+from cubicweb import _
+
+from cubicweb import RepositoryError
+
+
+ACTION_LABELS = {
+    'C': _('entity creation'),
+    'U': _('entity update'),
+    'D': _('entity deletion'),
+    'A': _('relation add'),
+    'R': _('relation removal'),
+    }
+
+
+class NoSuchTransaction(RepositoryError):
+    # Used by CubicWebException
+    msg = _("there is no transaction #%s")
+
+    def __init__(self, txuuid):
+        super(NoSuchTransaction, self).__init__(txuuid)
+        self.txuuid = txuuid
+
+class Transaction(object):
+    """an undoable transaction"""
+
+    def __init__(self, cnx, uuid, time, ueid):
+        self.cnx = cnx
+        self.uuid = uuid
+        self.datetime = time
+        self.user_eid = ueid
+
+    def _execute(self, *args, **kwargs):
+        """execute a query using either the req or the cnx"""
+        return self.cnx.execute(*args, **kwargs)
+
+
+    def __repr__(self):
+        return '<Transaction %s by %s on %s>' % (
+            self.uuid, self.user_eid, self.datetime)
+
+    def user(self):
+        """return the user entity which has done the transaction,
+        none if not found.
+        """
+        return self.cnx.find('CWUser', eid=self.user_eid).one()
+
+    def actions_list(self, public=True):
+        """return an ordered list of action effectued during that transaction
+
+        if public is true, return only 'public' action, eg not ones triggered
+        under the cover by hooks.
+        """
+        return self.cnx.transaction_actions(self.uuid, public)
+
+
+class AbstractAction(object):
+
+    def __init__(self, action, public, order):
+        self.action = action
+        self.public = public
+        self.order = order
+
+    @property
+    def label(self):
+        return ACTION_LABELS[self.action]
+
+    @property
+    def ertype(self):
+        """ Return the entity or relation type this action is related to"""
+        raise NotImplementedError(self)
+
+
+class EntityAction(AbstractAction):
+
+    def __init__(self, action, public, order, etype, eid, changes):
+        super(EntityAction, self).__init__(action, public, order)
+        self.etype = etype
+        self.eid = eid
+        self.changes = changes
+
+    def __repr__(self):
+        return '<%s: %s %s (%s)>' % (
+            self.label, self.eid, self.changes,
+            self.public and 'dbapi' or 'hook')
+
+    @property
+    def ertype(self):
+        """ Return the entity or relation type this action is related to"""
+        return self.etype
+
+
+class RelationAction(AbstractAction):
+
+    def __init__(self, action, public, order, rtype, eidfrom, eidto):
+        super(RelationAction, self).__init__(action, public, order)
+        self.rtype = rtype
+        self.eid_from = eidfrom
+        self.eid_to = eidto
+
+    def __repr__(self):
+        return '<%s: %s %s %s (%s)>' % (
+            self.label, self.eid_from, self.rtype, self.eid_to,
+            self.public and 'dbapi' or 'hook')
+
+    @property
+    def ertype(self):
+        """ Return the entity or relation type this action is related to"""
+        return self.rtype