anchor.diff:  (defgeneric prb-close-storage (storage)
     (:documentation "Release storage from use; further load & save operations cannot succeed without a subsequent open call"))
   
  -(defgeneric prb-load (storage id)
  -  (:documentation "Load the indicated object from storage (usually a node or tree)"))
  -
  -(defgeneric prb-save (storage id object)
  +(defgeneric prb-load (storage transaction location)
  +  (:documentation "Load the object at the indicated location from storage (usually a node or tree)"))
  +
  +(defgeneric prb-save (storage transaction location object)
     (:documentation "Save the indicated object in storage (usually a node or tree); 
  -    return a reference to its id within the storage"))
  +    return a reference to its location within the storage"))
   
   (defgeneric prb-commit (transaction-or-tree)
     (:documentation "Orchestrate the persisting of all changes to a tree, including all changed nodes"))
  
positive.code: 			 #'<))
  	(storage (storage (tree *rb-transaction*))))
      (loop for id in ids
         do (prb-save storage id (object-for-id *rb-transaction* id)))
      (when (new-root *rb-transaction*)
            (setf (root storage) (new-root *rb-transaction*))
        	  (setf (slot-value (tree *rb-transaction*) 'root) (new-root *rb-transaction*)))))
negative.code: (defun make-persistent-red-black-tree (&key ((:storage storage) (make-instance 'red-black-tree-memory-storage)))
    (with-rb-transaction ((make-instance 'persistent-red-black-tree :storage storage))))
  
  ;; (defun open-persistent-red-black-tree (storage-info)
  ;;   "Return a persisted red-black tree connected to its backing storage"
  ;;   (declare (ignorable storage-info))
  ;;   ;; TODO for now, we are using memory-based storage; we'll shift to file-based storage later
  ;;   (let* ((storage (make-instance 'red-black-tree-memory-storage))
  ;; 	 (tree (make-instance 'persistent-red-black-tree :storage storage)))
  ;;     (prb-open-storage storage)
  ;;     (prb-load storage *rb-transaction* tree)
  ;;     tree))
  
  (defmethod rb-node-class ((tree persistent-red-black-tree))
    'persistent-red-black-node)
  