diff --git a/concept.py b/concept.py
index 9a27490..d063d46 100644
--- a/concept.py
+++ b/concept.py
@@ -1,5 +1,5 @@
 #
-#  Copyright (c) 2011 Helmut Merz helmutm@cy55.de
+#  Copyright (c) 2012 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
@@ -18,8 +18,6 @@
 
 """
 Definition of the Concept and related classes.
-
-$Id$
 """
 
 from zope import component, schema
@@ -210,9 +208,26 @@ class Concept(Contained, Persistent):
         return [r.first for r in self.getParentRelations(predicates, sort=sort,
                                                 noSecurityCheck=noSecurityCheck)]
 
-    def assignChild(self, concept, predicate=None, order=0, relevance=1.0):
+    def checkPredicate(self, child, predicate=None):
+        cm = self.getConceptManager()
+        defaultPredicate = cm.getDefaultPredicate()
         if predicate is None:
-            predicate = self.getConceptManager().getDefaultPredicate()
+            predicate = defaultPredicate
+        if predicate == defaultPredicate:
+            subtypePred = cm.get('issubtype')
+            if subtypePred is not None:
+                subtypeRels = list(self.conceptType.getChildRelations(
+                                        [subtypePred], child.conceptType))
+                if subtypeRels:
+                    from loops.predicate import adaptedRelation
+                    rel = adaptedRelation(subtypeRels[0])
+                    predName = rel.usePredicate
+                    if predName and predName != u'standard':
+                        predicate = cm[predName]
+        return predicate
+
+    def assignChild(self, concept, predicate=None, order=0, relevance=1.0):
+        predicate = self.checkPredicate(concept, predicate)
         registry = component.getUtility(IRelationRegistry)
         rel = ConceptRelation(self, concept, predicate)
         if order != 0:
diff --git a/configure.zcml b/configure.zcml
index 908bb47..1692294 100644
--- a/configure.zcml
+++ b/configure.zcml
@@ -263,6 +263,15 @@
              set_schema="loops.interfaces.IPredicate" />
   </class>
 
+  <adapter factory="loops.predicate.IsSubtype"
+           provides="loops.interfaces.IIsSubtype" trusted="True" />
+  <class class="loops.predicate.IsSubtype">
+    <require permission="zope.View"
+             interface="loops.interfaces.IIsSubtype" />
+    <require permission="zope.ManageContent"
+             set_schema="loops.interfaces.IIsSubtype" />
+  </class>
+
   <!--<adapter factory="loops.predicate.MappingAttributeRelation" trusted="True" />
   <class class="loops.predicate.MappingAttributeRelation">
     <require permission="zope.View"
diff --git a/external/element.py b/external/element.py
index 7ce33fc..5c48146 100644
--- a/external/element.py
+++ b/external/element.py
@@ -1,5 +1,5 @@
 #
-#  Copyright (c) 2009 Helmut Merz helmutm@cy55.de
+#  Copyright (c) 2012 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
@@ -19,8 +19,6 @@
 """
 Basic implementation of the elements used for the intermediate format for export
 and import of loops objects.
-
-$Id$
 """
 
 import os
@@ -38,6 +36,7 @@ from loops.interfaces import IConceptSchema
 from loops.external.interfaces import IElement
 from loops.i18n.common import I18NValue
 from loops.layout.base import LayoutNode
+from loops.predicate import adaptedRelation
 from loops.view import Node
 
 
@@ -138,14 +137,26 @@ class ChildElement(Element):
     elementType = 'child'
     posArgs = ('first', 'second', 'predicate', 'order', 'relevance')
 
-    def __init__(self, *args):
+    def __init__(self, *args, **kw):
         for idx, arg in enumerate(args):
             self[self.posArgs[idx]] = arg
+        for k, v in kw.items():
+            self[k] = v
 
     def execute(self, loader):
         loader.assignChild(self['first'], self['second'], self['predicate'],
                            order = self.get('order') or 0,
                            relevance = self.get('relevance') or 1.0)
+        additionalParams = [(k, v) for k, v in self.items()
+                                   if k not in self.posArgs]
+        if additionalParams:
+            pred = loader.getPredicate(self['predicate'])
+            first = loader.concepts[self['first']]
+            second = loader.concepts[self['second']]
+            relation = first.getChildRelations([pred], child=second)[0]
+            adaptedRel = adaptedRelation(relation)
+            for attr, value in additionalParams:
+                setattr(adaptedRel, attr, value)
 
 
 class ResourceElement(Element):
diff --git a/interfaces.py b/interfaces.py
index 36c5050..a552743 100644
--- a/interfaces.py
+++ b/interfaces.py
@@ -1,5 +1,5 @@
 #
-#  Copyright (c) 2011 Helmut Merz helmutm@cy55.de
+#  Copyright (c) 2012 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
@@ -18,8 +18,6 @@
 
 """
 loops interface definitions.
-
-$Id$
 """
 
 from zope.interface import Interface, Attribute
@@ -761,6 +759,16 @@ class IRelationAdapter(Interface):
     """
 
 
+class IIsSubtype(IRelationAdapter):
+
+    usePredicate = schema.TextLine(
+            title=_(u'Use Predicate'),
+            description=_(u'The name of the predicate that should be used'
+                    u'for relations between concepts of these types.'),
+            default=u'standard',
+            required=False)
+
+
 # probably not useful
 class xxIMappingAttributeRelation(IConceptSchema):
     """ A relation based on a predicate ('mappingAttribute') that provides
diff --git a/predicate.py b/predicate.py
index 676a88e..ba69752 100644
--- a/predicate.py
+++ b/predicate.py
@@ -1,5 +1,5 @@
 #
-#  Copyright (c) 2008 Helmut Merz helmutm@cy55.de
+#  Copyright (c) 2012 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
@@ -18,8 +18,6 @@
 
 """
 Definition and management of special predicates and corresponding relations.
-
-$Id$
 """
 
 from zope import component, schema
@@ -31,7 +29,8 @@ from zope.security.proxy import removeSecurityProxy
 from zope.traversing.api import getName
 
 from loops.interfaces import ILoopsObject, IConcept, IResource, IConceptRelation
-from loops.interfaces import IPredicate, IRelationAdapter #, IMappingAttributeRelation
+from loops.interfaces import IPredicate, IRelationAdapter
+from loops.interfaces import IIsSubtype     #, IMappingAttributeRelation
 from loops.concept import Concept
 from loops.common import adapted, AdapterBase
 from loops.type import TypeInterfaceSourceList
@@ -89,8 +88,20 @@ def adaptedRelation(relation):
 
 # standard relation adapters
 
-#PredicateInterfaceSourceList.predicateInterfaces += (IMappingAttributeRelation,)
+PredicateInterfaceSourceList.predicateInterfaces += (
+        IIsSubtype,)
 
+class IsSubtype(RelationAdapter):
+    """ Allows specification of a predicate for relations between concepts
+        of certain types.
+    """
+
+    implements(IIsSubtype)
+
+    _contextAttributes = list(IIsSubtype)
+
+
+#PredicateInterfaceSourceList.predicateInterfaces += (IMappingAttributeRelation,)
 
 #class MappingAttributeRelation(AdapterBase):
 
diff --git a/tests/setup.py b/tests/setup.py
index 77250d3..3097e29 100644
--- a/tests/setup.py
+++ b/tests/setup.py
@@ -64,10 +64,12 @@ from loops.config.base import GlobalOptions, LoopsOptions
 from loops.config.base import QueryOptions, PredicateOptions, TypeOptions
 from loops.interfaces import ILoopsObject, IIndexAttributes
 from loops.interfaces import IDocument, IFile, ITextDocument
+from loops.interfaces import IIsSubtype
 from loops.layout.base import LayoutNode
 from loops.organize.memberinfo import MemberInfoProvider
 from loops.organize.stateful.base import StatefulResourceIndexInfo, handleTransition
-from loops.predicate import Predicate   #, MappingAttributeRelation
+from loops.predicate import Predicate
+from loops.predicate import IsSubtype#, MappingAttributeRelation
 from loops.expert.concept import QueryConcept
 from loops.resource import Resource, FileAdapter, TextDocumentAdapter
 from loops.resource import Document, MediaAsset
@@ -135,6 +137,7 @@ class TestSite(object):
         component.provideAdapter(LoopsType)
         component.provideAdapter(ConceptType)
         component.provideAdapter(Predicate)
+        component.provideAdapter(IsSubtype, provides=IIsSubtype)
         #component.provideAdapter(MappingAttributeRelation)
         component.provideAdapter(ResourceType, (IDocument,))
         component.provideAdapter(TypeConcept)