public InitialReceiver(String stream, Fields allFields) {
// TODO: don't want to project for non-batch bolts...???
// how to distinguish "batch" streams from non-batch streams?
_stream = stream;
_factory = new RootFactory(allFields);
List<String> projected = new ArrayList(allFields.toList());
projected.remove(0);
_project = new ProjectionFactory(_factory, new Fields(projected));
}