UUID: A unique identifier for a particular item.

Tombstone: An indicator that an item with a given UUID once existed but no longer does.

G-Set: a "grow only" set; elements may only ever be appended.

Last Write Wins (LWW): a g-set of changes with their own UUID and timestamp per revision; the entry with the highest timestamp is the current value.

Grow Only Sets

Removing items

A g-set indicates items ever added to the set.

A second g-set is added to track which IDs have been revoked from the set.

This tracking of removed items is tombstoning; the data of that item may no longer be kept but its UUID is kept forever to indicate it should no longer be here.

Toggling properties of an item; ex. in a to do list

A last write wins set can store whenever the property is changed such as the "checked" state.