 +            The contained response will have a status code of
 +            L{responsecode.BAD_REQUEST}.
 +        """
-+        if resource is None or child_path is None:
++        if parent is None or child_name is None:
 +            return None
-+        
-+        url = joinURL(self.urlForResource(resource), child_path)
++
++        url = joinURL(self.urlForResource(parent), child_name)
 +
 +        cached = self._urlsByResource.get(url, None)
 +        if cached is not None:
 +            return succeed(cached)
 +
-+        segment = unquote(child_path)
++        assert "/" not in child_name, "Child name may not contain '/': %s" % (child_name,)
++
++        segment = unquote(child_name)
 +
 +        def notFound(f):
 +            f.trap(http.HTTPError)

         #
         # Parse the URL
         #
@@ -414,11 +431,53 @@
         def notFound(f):
             f.trap(http.HTTPError)
             if f.response.code != responsecode.NOT_FOUND:

+        d.addErrback(notFound)
+        return d
 
+    def locateChildResource(self, parent, child_name):
+        """
+        Looks up the child resource with the given name given the parent
+        resource.  This is similar to locateResource(), but doesn't have to
+        start the lookup from the root resource, so it is potentially faster.
+        @param parent: the parent of the resource being looked up.
+        @param child_name: the name of the child of C{parent} to looked up.
+            to C{parent}.
+        @return: a L{Deferred} resulting in the L{IResource} at the
+            given URL or C{None} if no such resource can be located.
