def getItems(nodeIdentifier, requestor, maxItems=None, itemIdentifiers=[]):
    """ Retrieve items from persistent storage

        If C{maxItems} is given, return the C{maxItems} last published
        items, else if C{itemIdentifiers} is not empty, return the items
        requested.  If neither is given, return all items.

        @return: a deferred that returns the requested items
        """
