diff --git a/common.py b/common.py
index c4b866f..763c8ac 100644
--- a/common.py
+++ b/common.py
@@ -219,9 +219,11 @@ class NameChooser(BaseNameChooser):
         '\xdc': 'Ue', '\xfc': 'ue', '\xdf': 'ss'}
 
 
-# virtual attributes
+# virtual attributes/properties
 
-class ContainerAttribute(object):
+#class ContainerAttribute(object):
+#class ContainedCollection(object):
+class TypeInstances(object):
     """ Use objects within a ConceptManager object for a collection attribute.
     """
 
@@ -237,6 +239,14 @@ class ContainerAttribute(object):
     def typeConcept(self):
         return self.context[self.typeName]
 
+    @Lazy
+    def typeToken(self):
+        return 'loops:concept:' + self.typeName
+
+    @Lazy
+    def typePredicate(self):
+        return self.context.getTypePredicate()
+
     def create(self, id, **kw):
         from loops.concept import Concept
         from loops.setup import addAndConfigureObject
@@ -250,11 +260,17 @@ class ContainerAttribute(object):
         del self.context[self.prefix + id]
 
     def get(self, id, default=None, langInfo=None):
-        return adapted(self.context.get(self.prefix + id, default),
-                       langInfo=self.langInfo)
+        #return adapted(self.context.get(self.prefix + id, default),
+        #               langInfo=self.langInfo)
+        from loops.expert import query
+        result = (query.Identifier(id) & query.Type(self.typeToken)).apply()
+        for obj in query.getObjects(result):
+            return adapted(obj, langInfo=self.langInfo)
+        else:
+            return default
 
     def __iter__(self):
-        for c in self.typeConcept.getChildren([self.context.getTypePredicate()]):
+        for c in self.typeConcept.getChildren([self.typePredicate]):
             yield adapted(c, langInfo=self.langInfo)
 
 
@@ -318,6 +334,29 @@ class ChildRelationSet(RelationSet):
             yield adapted(c, langInfo=self.langInfo)
 
 
+# property descriptors
+
+class RelationSetProperty(object):
+
+    def __init__(self, predicateName):
+        self.predicateName = predicateName
+
+    def __get__(self, inst, class_=None):
+        if inst is None:
+            return self
+        return self.factory(inst, self.predicateName)
+
+
+class ParentRelationSetProperty(RelationSetProperty):
+
+    factory = ParentRelationSet
+
+
+class ChildRelationSetProperty(RelationSetProperty):
+
+    factory = ChildRelationSet
+
+
 # caching (TBD)
 
 def cached(obj):
diff --git a/concept.py b/concept.py
index 4321f70..b41d691 100644
--- a/concept.py
+++ b/concept.py
@@ -397,13 +397,18 @@ class IndexAttributes(object):
     def __init__(self, context):
         self.context = context
 
+    @Lazy
+    def adapted(self):
+        return adapted(self.context)
+
     def text(self):
-        ctx = self.context
+        #ctx = self.context
         #return ' '.join((getName(ctx), ctx.title,))
-        description = ctx.description
+        description = self.context.description
         if isinstance(description, I18NValue):
             description = ' '.join(description.values())
-        actx = adapted(ctx)
+        #actx = adapted(ctx)
+        actx = self.adapted
         indexAttrs = getattr(actx, '_textIndexAttributes', ())
         #return ' '.join([getName(ctx), ctx.title, ctx.description] +
         return ' '.join([self.title(), description] +
@@ -431,6 +436,12 @@ class IndexAttributes(object):
                 creators.append(principal.title)
         return creators
 
+    def identifier(self):
+        id = getattr(self.adapted, 'identifier', None)
+        if id is None:
+            return getName(self)
+        return id
+
 
 # events
 
diff --git a/expert/query.py b/expert/query.py
index f7a0cec..3519deb 100644
--- a/expert/query.py
+++ b/expert/query.py
@@ -41,6 +41,7 @@ from loops import util
 titleIndex = ('', 'loops_title')
 textIndex = ('', 'loops_text')
 typeIndex = ('', 'loops_type')
+identifierIndex = ('', 'loops_identifier')
 stateIndex = ('', 'loops_state')
 
 
@@ -54,6 +55,10 @@ def Title(value):
 def Text(value):
     return BaseText(textIndex, value)
 
+@implementer(IQuery)
+def Identifier(value):
+    return Eq(identifierIndex, value)
+
 @implementer(IQuery)
 def Type(value):
     if value.endswith('*'):
diff --git a/interfaces.py b/interfaces.py
index b4fdeda..24eb26a 100644
--- a/interfaces.py
+++ b/interfaces.py
@@ -586,13 +586,13 @@ class IConceptRelation(IDyadicRelation):
 # interfaces for catalog indexes
 
 class IIndexAttributes(Interface):
-    """ Attributes odr methods providing index values. Typically provided
+    """ Attributes or methods providing index values. Typically provided
         by an adapter.
     """
 
     def title():
         """ Return a text containing title and similar attributes to be
-            indexed by a full-text index.
+            indexed by the title index.
         """
 
     def text():
@@ -603,6 +603,11 @@ class IIndexAttributes(Interface):
         """ Return a string that identifies the type of the object.
         """
 
+    def identifier():
+        """ Returns a value that may be used for identifying an object within
+            a restricted range, e.g. the instances of a type.
+        """
+
 
 # types stuff
 
diff --git a/resource.py b/resource.py
index 1c05fc9..728554d 100644
--- a/resource.py
+++ b/resource.py
@@ -535,6 +535,9 @@ class IndexAttributes(object):
                 creators.append(principal.title)
         return creators
 
+    def identifier(self):
+        return getName(self)
+
 
 class ResourceTypeSourceList(object):
 
diff --git a/tests/setup.py b/tests/setup.py
index 2102d1d..d056dcb 100644
--- a/tests/setup.py
+++ b/tests/setup.py
@@ -157,6 +157,7 @@ class TestSite(object):
         component.provideUtility(catalog, ICatalog)
         catalog['loops_title'] = TextIndex('title', IIndexAttributes, True)
         catalog['loops_text'] = TextIndex('text', IIndexAttributes, True)
+        catalog['loops_identifier'] = FieldIndex('identifier', IIndexAttributes, True)
         catalog['loops_type'] = FieldIndex('tokenForSearch', IType, False)
         catalog['loops_state'] = KeywordIndex('tokens', IStatefulIndexInfo, False)
         component.provideAdapter(ConceptIndexAttributes)