diff --git a/product/ERP5/interfaces/solver.py b/product/ERP5/interfaces/solver.py
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+# -*- coding: utf-8 -*-
+##############################################################################
+#
+# Copyright (c) 2009 Nexedi SARL and Contributors. All Rights Reserved.
+#                    Łukasz Nowak <luke@nexedi.com>
+#
+# WARNING: This program as such is intended to be used by professional
+# programmers who take the whole responsibility 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
+# guarantees and support are strongly advised 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.
+#
+##############################################################################
+
+from zope.interface import Interface
+
+class ISolver(Interface):
+  """Target Solver interface specification
+
+  This interface must be implemented by all target solvers
+  which are used to solve divergences in ERP5 simulation. Documents
+  which implement ITargetSolver provide a solve method.
+
+  Besides ITargetSolver static interface definition, target solvers
+  must support IDeliveryGetter to access simulation movements to solve.
+
+  TODO-XXX: 
+    - find a way to make static interfaces inherit from
+      dynamic interfaces in ERP5 (ex. solver process workflow)
+    - IDeliveryGetter is not appropriate name / interface
+    - find a way to define at which level to solve divergences
+      (ex. line, delivery)
+  """
+  def solve():
+    """
+    Start the solving process (and trigger the workflow method
+    in solver_process_workflow). At the end the solving process,
+    appropriate methods of the solver_process_workflow must be invoked
+    (ex. succeed, fail, abort).
+
+    NOTE: the solve method is invoked to solve divergences or to 
+    optimize movements. Examples include: Adopt, Accept, Reduce,
+    Postpone, Optimize Critical Path, 
+    """
+
+  def isSolving():
+    """
+    Returns True if the solver processing in ongoing. False else.
+    """
+
+  def isSolved():
+    """
+    Returns True if all divergences are solved, False else.
+    """
+
+  def isFailed():
+    """
+    Returns True if divergence resolution fails. False else.
+    """
+
+  def isAborted():
+    """
+    Returns True if divergence resolution was aborted. False else.
+    """
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