--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_thesaurus/schema.py	Tue Apr 14 17:52:05 2015 +0200
@@ -0,0 +1,86 @@
+#
+# 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.schema.interfaces import IObject, IList, SchemaNotProvided
+
+# import packages
+from zope.interface import implementer, Interface
+from zope.schema import Object, List, Set, Choice, TextLine
+
+
+class IThesaurusTermField(IObject):
+    """Marker interface to define a thesaurus term field"""
+
+    thesaurus_name = TextLine(title="Thesaurus name",
+                              required=False)
+
+    extract_name = TextLine(title="Extract name",
+                            required=False)
+
+
+class IThesaurusTermsListField(IList):
+    """Marker interface to define a list of thesaurus terms"""
+
+    thesaurus_name = TextLine(title="Thesaurus name",
+                              required=False)
+
+    extract_name = TextLine(title="Extract name",
+                            required=False)
+
+
+@implementer(IThesaurusTermField)
+class ThesaurusTermField(Object):
+    """Thesaurus term schema field"""
+
+    def __init__(self, schema=None, thesaurus_name=u'', extract_name=u'', **kw):
+        super(ThesaurusTermField, self).__init__(schema=Interface, **kw)
+        self.thesaurus_name = thesaurus_name
+        self.extract_name = extract_name
+
+    def _validate(self, value):
+        super(Object, self)._validate(value)
+        # schema has to be provided by value
+        if not self.schema.providedBy(value):
+            raise SchemaNotProvided
+
+
+@implementer(IThesaurusTermsListField)
+class ThesaurusTermsListField(List):
+    """Thesaurus terms list schema field"""
+
+    def __init__(self, value_type=None, unique=False, thesaurus_name=u'', extract_name=u'', **kw):
+        super(ThesaurusTermsListField, self).__init__(value_type=Object(schema=Interface), unique=False, **kw)
+        self.thesaurus_name = thesaurus_name
+        self.extract_name = extract_name
+
+
+class ValidatedSet(Set):
+    """A set field validated when not bound to a context"""
+
+    def _validate(self, value):
+        # Don't try to validate with empty context !
+        if self.context is None:
+            return
+        super(ValidatedSet, self)._validate(value)
+
+
+class ValidatedChoice(Choice):
+    """An always validated choice field"""
+
+    def _validate(self, value):
+        pass