Data Hoarding

Data hoarding releases currency, therefore changes object semantics. A receiver
hoards replicas from a sender and each replica is denoted as (objectID, semantics),
where semantics is either primary or copy.

General hoarding (G-hoarding): sender owns the primary of an object, i.e.
(objectID, primary), and receiver hoards a copy from the sender. After G-hoarding,
sender still owns the primary, i.e. sender (objectID, primary), and receiver
(objectID, copy).

Primary hoarding (P-hoarding): sender owns the primary of the object, i.e. (objectID,
primary), and receiver hoards the primary from the sender. After P-hoarding, the
primary is transferred from the sender to the receiver and the one in the sender
becomes a copy, i.e. sender (objectID, copy), and receiver (objectID, primary).

Copy hoarding (C-hoarding): sender owns only the copy of the object, i.e. (objectID,
copy), and receiver hoards a copy from the sender. After C-hoarding, both the sender
and the receiver hold copies, i.e. sender (objectID, copy), and receiver (objectID, copy).