[Infrastructures] state machines

[u+infra-terraluna-jmto@chalmers.se]

Wesley,

On Tue, Sep 19, 2006 at 09:44:12AM -0400, Wesley Craig wrote:
> Stated so generally, I think I can come up with counter examples.   
> For instance, if you make a full disk image before pushing out a  
> change, you can in fact "undo" the change, by restoring the backup.

what you propose is reserving a lot of space for rollbacks, which
is going to be expensive, and yet a change which erases
the code for reading the saved image will be irreversible.

Of course testing and debugging the reversal for each change makes it
_possible_ but that does not seem to be the point, if we look at
the original statement, which you happened to cite:

> On 18 Sep 2006, at 19:03, Steve Traugott wrote:
> >    ... Creating the transition code for each reverse
> >    edge, and performing the inspection to ensure that the code
> >    re-creates the prior state, will always be more expensive than
> >    just hitting the big "reset" button and rebuilding the machine

Rune.