diff --git a/relation/README.txt b/relation/README.txt
index 7105cfc..e3bd983 100644
--- a/relation/README.txt
+++ b/relation/README.txt
@@ -159,6 +159,14 @@ It is also possible to remove a relation from the relation registry:
   >>> nyRels[0].first == kirk
   True
 
+The relation registry also provides unique ids for all relations
+registered and all objects taking part in these relations. This unique
+ids may be used e.g. if relationships or predicates are themselves
+content objects.
+
+  >>> relations.getUniqueIdForObject(kirk)
+  7
+
 
 Triadic Relations
 ~~~~~~~~~~~~~~~~~
@@ -305,6 +313,12 @@ a relation registry; it allows to query for more than one relationship:
   >>> len(getRelations(first=clark, relationships=[LivesIn]))
   1
 
+The relation registry also supports the getUniqueIdForObject() method that
+just returns the intid of the object given:
+
+  >>> relations.getUniqueIdForObject(kirk)
+  1
+
 
 Handling object removal
 ~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/relation/interfaces.py b/relation/interfaces.py
index 0abcbd4..90036e5 100644
--- a/relation/interfaces.py
+++ b/relation/interfaces.py
@@ -131,6 +131,11 @@ class IRelationRegistryUpdate(Interface):
         """ Remove the relation given from this registry.
         """
 
+    def getUniqueIdForObject(object):
+        """ Return an identifier for the object given that is unique at
+            least within the scope of this registry.
+        """
+
 
 class IRelationRegistryQuery(Interface):
     """ Interface for querying a relation registry.
@@ -155,4 +160,3 @@ class IRelationRegistry(IRelationRegistryUpdate, IRelationRegistryQuery):
         implemented as a local utility .
     """
 
-
diff --git a/relation/registry.py b/relation/registry.py
index 2ff04e6..c5f8674 100644
--- a/relation/registry.py
+++ b/relation/registry.py
@@ -45,15 +45,27 @@ class DummyRelationRegistry(object):
 
     def __init__(self):
         self.relations = []
+        self.objects = []
 
     def register(self, relation):
         if relation not in self.relations:
             self.relations.append(relation)
+        if relation not in self.objects:
+            self.objects.append(relation)
+        for attr in ('first', 'second', 'third',):
+            value = getattr(relation, attr, None)
+            if value is not None and value not in self.objects:
+                self.objects.append(value)
     
     def unregister(self, relation):
         if relation in self.relations:
             self.relations.remove(relation)
             notify(RelationInvalidatedEvent(relation))
+
+    def getUniqueIdForObject(self, obj):
+        if obj in self.objects:
+            return self.objects.index(obj)
+        return None
     
     def query(self, example=None, **kw):
         result = []
@@ -66,6 +78,8 @@ class DummyRelationRegistry(object):
             criteria['relationship'] = example
         criteria.update(kw)
         for r in self.relations:
+            if r is None:
+                continue
             hit = True
             for k in criteria:
                 if ((k == 'relationship'
@@ -100,6 +114,9 @@ class RelationRegistry(Catalog):
         self.unindex_doc(zapi.getUtility(IIntIds).getId(relation))
         notify(RelationInvalidatedEvent(relation))
 
+    def getUniqueIdForObject(self, obj):
+        return zapi.getUtility(IIntIds).getId(obj)
+
     def query(self, example=None, **kw):
         intIds = zapi.getUtility(IIntIds)
         criteria = {}