rlock = new Object();
rlock = new ReadLock();
    private void initializeTransients() {	pcs = new PropertyChangeSupport(this);	ddeps = new HashMap<String,DataFrame>();	rdeps = new HashMap<String,List<RelationFrame>>();	slot_map = new HashMap<String,String>();	path_dependents = new HashMap<String,Set<DataFrame>>();	rlock = new Object();    }