Comment by Animats
2 years ago
Classically, this is a problem in hardware logic design. It's desirable that logic circuits not be able to lock up in an invalid state. So having a state machine where invalid states cannot be represented is useful. Hardware without this property tends to need reset buttons.
The abstract concept here is liveness, aka "eventually something good will happen". In practise, liveness alone is insufficient because a locked up program/processor is indistinguishable from a very slow program/processor. So you really want bounded liveness, along the lines of "within X time units, something good will happen".