.accounting
-----------
A subsystem for transaction processing, storage and historical
measurement.


.pnl
----
BEP, the break even price: the price at which liquidating
a remaining position results in a zero PnL since the position was
"opened" in the destination asset.

PPU: price-per-unit: the "average cost" (in cumulative mean terms)
of the "entry" transactions which "make a position larger"; taking
a profit relative to this price means that you will "make more
profit then made prior" since the position was opened.