 +        d.addErrback(notFound)
 +        return d
  
-+    def locateChildResource(self, resource, child_path):
++    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 resource: the parent of the resource being looked up.
-+        @param child_path: the path of the resource being looked up, relative
++        @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.

+                return f
+            return None
+
+        d = defer.maybeDeferred(self._getChild, None, resource, [segment], updatepaths=False)
+        d.addCallback(self._rememberResource, url)
+        d.addErrback(notFound)
+        return d

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