diff --git a/product/ERP5/PropertySheet/TradeConditionConstraint.py b/product/ERP5/PropertySheet/TradeConditionConstraint.py
new file mode 100644
index 0000000000000000000000000000000000000000..8e64dcc4210625f7faaf48900cd3ef68a7b3a695
--- /dev/null
+++ b/product/ERP5/PropertySheet/TradeConditionConstraint.py
@@ -0,0 +1,61 @@
+##############################################################################
+#
+# Copyright (c) 2009 Nexedi SA and Contributors. All Rights Reserved.
+#                    Fabien Morin <fabien@nexedi.com>
+#
+# WARNING: This program as such is intended to be used by professional
+# programmers who take the whole responsability of assessing all potential
+# consequences resulting from its eventual inadequacies and bugs
+# End users who are looking for a ready-to-use solution with commercial
+# garantees and support are strongly adviced to contract a Free Software
+# Service Company
+#
+# 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.
+#
+##############################################################################
+
+class TradeConditionConstraint:
+  """
+   Trade Model Line Constraints
+  """
+  _constraints = (
+    { 'id'            : 'reference_existence',
+      'description'   : 'Property reference must be defined',
+      'type'          : 'PropertyExistence',
+      'reference'    : None,
+      "message_property_not_set" : 'Reference must be defined',
+      "message_no_such_property" : 'Reference must be defined'
+    },
+    { 'id'            : 'effective_date_existence',
+      'description'   : 'Property start_date must be defined',
+      'type'          : 'PropertyExistence',
+      'effective_date'    : None,
+      'message_property_not_set': 'Effective Date must be defined',
+      'message_no_such_property' : 'Effective Date must be defined'
+    },
+    { 'id'            : 'date_coherency',
+      'description'   : 'Expiration Date must be after Effective Date',
+      'type'          : 'TALESConstraint',
+      'expression'    : 'python: object.getExpirationDate() >= object.getEffectiveDate()',
+      'message_expression_false': 'Expiration Date must be after Begin Date',
+    },
+    { 'id'            : 'version_existence',
+      'description'   : 'Version must be defined',
+      'type'          : 'PropertyExistence',
+      'version'         :  None,
+      'message_property_not_set': 'Version must be defined',
+      'message_no_such_property' : 'Version must be defined',
+    },
+  )