add definitions for relation and relation set schema fields

git-svn-id: svn://svn.cy55.de/Zope3/src/loops/trunk@3162 fd906abe-77d9-0310-91a1-e0d9ade77398

schema.py

@@ -1,5 +1,5 @@
 #
-#  Copyright (c) 2005 Helmut Merz helmutm@cy55.de
+#  Copyright (c) 2009 Helmut Merz helmutm@cy55.de
 #
 #  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
@@ -17,16 +17,64 @@
 #
 
 """
-Specialized schema factories
+Specialized fields and schema factories
 
 $Id$
 """
 
 from zope.component import adapts
+from zope.interface import Attribute, implements
+from zope.schema import Choice, List
+from zope.schema.interfaces import IChoice, IList
 
 from cybertools.composer.schema.factory import SchemaFactory
 from loops.interfaces import IResourceAdapter, IFile, INote
 
+# fields
+
+class IRelation(IChoice):
+    """ An object addressed via a single relation.
+    """
+
+    target_types = Attribute('A list of names that denote types of '
+                'loops objects (typically concept types) that may be used as '
+                'targets for the relation.')
+
+
+class IRelationSet(IList):
+    """ A collection of objects addressed via a set of relations.
+
+        Despite its name, the collection may have a predefined order.
+    """
+
+    target_types = Attribute('A list of names that denote types of '
+                'loops objects (typically concept types) that may be used as '
+                'targets for the relations.')
+
+
+class Relation(Choice):
+
+    implements(IRelation)
+
+    __typeInfo = ('relation',)
+
+    def __init__(self, *args, **kw):
+        self.target_types = kw.pop('target_types')
+        super(Relation, self).__init__(*args, **kw)
+
+
+class RelationSet(List):
+
+    implements(IRelationSet)
+
+    __typeInfo = ('relationset',)
+
+    def __init__(self, *args, **kw):
+        self.target_types = kw.pop('target_types')
+        super(RelationSet, self).__init__(*args, **kw)
+
+
+# schema factories
 
 class ResourceSchemaFactory(SchemaFactory):