diff --git a/expert/README.txt b/expert/README.txt
index 257f29b..4aece02 100644
--- a/expert/README.txt
+++ b/expert/README.txt
@@ -187,10 +187,12 @@ concepts) that are direct or indirect children of jim.
   >>> sorted(o.title for o in getObjects((qu & fltr.query()).apply()))
   [u'Doc 001', u'Doc 003']
 
-  >>> #fltr.check(concepts['d001.txt'])
-  >>> #fltr.check(concepts['d002.txt'])
-  >>> #objs = fltr.apply(objs)
-  >>> #sorted(o.title for o in objs.values())
+  >>> #fltr.check(resources['d001.txt'])
+  >>> #fltr.check(resources['d002.txt'])
+  >>> r1 = qu.apply()
+  >>> r2 = fltr.apply(dict(zip(r1, getObjects(r1))))
+  >>> sorted(o.title for o in r2.values())
+  [u'Doc 001', u'Doc 003']
 
 
 Organizing Queries and Filters with Query Instances
diff --git a/expert/filter.py b/expert/filter.py
index 2c4eb5b..4ae52b0 100644
--- a/expert/filter.py
+++ b/expert/filter.py
@@ -28,22 +28,31 @@ from zope.interface import implements
 from cybertools.catalog.query import And
 from loops.expert.interfaces import IFilter
 from loops.expert.query import Children as ChildrenQuery
+from loops import util
 
 
 class Filter(object):
 
     implements(IFilter)
 
+    query = None
+
     def __init__(self, **kw):
         self.kwargs = kw
 
     def apply(self, objects, queryInstance=None):
+        qu = self.query()
+        #if qu is not None:
+        #    return set(objects).intersection(qu.apply())
         result = IOBTree()
-        for uid, obj in objects:
-            if self.check(obj, queryInstance):
+        for uid, obj in objects.items():
+            if self.check(uid, obj, queryInstance):
                 result[uid] = obj
         return result
 
+    def check(self, uid, obj, queryInstance=None):
+        return uid in self.query().apply()      #.keys()
+
 
 class Children(Filter):
 
diff --git a/expert/interfaces.py b/expert/interfaces.py
index e9c1912..1f5f582 100644
--- a/expert/interfaces.py
+++ b/expert/interfaces.py
@@ -26,7 +26,7 @@ from zope.interface import Interface, Attribute
 
 
 class IQuery(Interface):
-    """ A query or
+    """ A query.
     """
 
     def apply():
@@ -68,7 +68,7 @@ class IFilter(Interface):
             intermediate results.
         """
 
-    def check(obj, queryInstance=None):
+    def check(uid, obj, queryInstance=None):
         """ Return True if the object given should be included in the
             filter's result set, False otherwise.