Cost
What a cost quantity is denominated in.
The cost package forms its line items in two different denominations, and each is the natural one for its line: a holding charge really is a rate, and an ordering charge really is a per-event amount. The two cannot be added without first being brought to a common denomination, which is what this enum exists to make checkable rather than a matter of reading the calculators.
It serves two purposes, which are the same question asked twice. On a CostLine it states what that line is denominated in. Passed to a rollup, it asks for the total in that denomination — and since a rollup spans lines of both kinds, there is no total it can report until the caller says which.
Both denominations are valid and neither is preferred. The per-unit-time form is independent of how long the replication ran and is the one to compare runs of unequal length with; the per-replication form is the more intuitive reading and matches the way the inventory trade-off is usually posed.
Entries
Dollars per unit of the modeler's time unit. A line denominated this way is formed as a time-weighted average times a rate, so its value does not depend on how long the replication observed. Multiply by the observed window to obtain dollars.
Dollars accumulated over one replication's observed window — its ending time less its warm-up. A line denominated this way is formed as a counter times a $/event constant, so its value grows with how long the replication observed. Divide by the observed window to obtain a rate.