⟩ Distinguish among erase, erase permanent, erase selective and erase all?
Erase cancels the membership of a record in specific set occurrences and removes only the named record.
Erase permanent removes the specific record and all mandatory occurrences it owns. It disconnects all optional members.
Erase selective removes the record, all mandatory members and all optional members not connected to other sets. It disconnects those that are connected.
Erase all removes the specified record and all the mandatory and optional records it owns.
