Transaction Tape

A time-ordered list of state changes to a system. When applied in time order to an Advancer the previous state of the system can be recreated. If the current state is stored and state changes are reversible then the tape can be truncated at the beginning without affecting the current state; it merely limits how far back you can go.

Known uses for this pattern (TransactionTape plus an Advancer) include portfolio management and cricket scoreboards. C.f. undo and the command pattern. -- HubertMatthews

An InstanceNote might be used as follows:

• 20140801`20140831`TransactionTape(RecentChanges`August`2014)

where a beginning date followed by an ending date include the first and last dates included in the transactions of the TransactionTape named RecentChanges`August`2014.

What would such a note be used for?

See revised InstanceNote