It would seem that any good computer system should provide a way to snapshot the entire state of the system—to make a duplicate of the state of the system to be used in case of catastrophe.

The Mondex card is a computer system for which it is vital that there be no such snapshot ability, for that would be tantamount to duplicating currency.

It is not generally easy to know how to address conflicting goals but these problems can be ameliorated. The worst that happens, generally is that there are some limitations on the grand simple goals.

In the 370 Keykos we provided a tape checkpoint facility with no provisions for an application to opt out. Seeing as how many applications dealt with device keys that would expire upon upon restart from a checkpoint, it was obviously possible to cope with edge of the world semantics. An object that refused duplication would appear to be beyond the edge, just as did device keys.

Just because some applications are able and choose to opt out, does not mean that all can. Here is a scenario from some future personal computer.