--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_i18n/interfaces/__init__.py	Thu Feb 19 10:55:01 2015 +0100
@@ -0,0 +1,84 @@
+#
+# Copyright (c) 2008-2015 Thierry Florac <tflorac AT ulthar.net>
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+
+__docformat__ = 'restructuredtext'
+
+
+# import standard library
+
+# import interfaces
+from zope.interface import Interface, invariant, Invalid
+
+# import packages
+from zope.schema import Choice, Set, Bool
+
+from pyams_i18n import _
+
+
+LANGUAGE_POLICIES = ('server',
+                     'session',
+                     'browser',
+                     'browser --> session --> server',
+                     'browser --> server',
+                     'session --> browser --> server',
+                     'session --> server')
+
+LANGUAGE_CACHE_KEY = 'pyams_i18n.language.cache'
+
+
+class INegotiator(Interface):
+    """Local negotiator utility manager interface."""
+
+    policy = Choice(title=_("Language lookup policy"),
+                    description=_("Defines how the language lookup is working."),
+                    values=LANGUAGE_POLICIES,
+                    default='session --> browser --> server',
+                    required=True)
+
+    server_language = Choice(title=_("Server language"),
+                             description=_("The language used for server policy."),
+                             vocabulary='PyAMS base languages',
+                             default='en',
+                             required=True)
+
+    offered_languages = Set(title=_("Offered languages"),
+                            description=_("A list of offered languages. Can be used to "
+                                          "user select languages which are offered in "
+                                          "a skin."""),
+                            value_type=Choice(vocabulary='PyAMS base languages'),
+                            default={'en', },
+                            required=False)
+
+    cache_enabled = Bool(title=_("Language caching enabled"),
+                         description=_("Language caching enabled (per request)"),
+                         default=False)
+
+    @invariant
+    def check_policy(self):
+        if self.policy not in LANGUAGE_POLICIES:
+            raise Invalid(_("Unsupported language policy"))
+
+    def get_language(self, request):
+        """Return the matching language to use.
+
+        If no match is found, None is returned.
+        """
+
+    def clear_cache(self, request):
+        """Clear cached language value"""
+
+
+class IUserPreferredLanguage(Interface):
+    """This interface provides language negotiation based on user preferences"""
+
+    def get_language(self):
+        """Return main user preferred language"""