Re: [boost] Re: Re: [prereview request][fsm]

From: E. Gladyshev (eegg_at_[hidden])
Date: 2004-05-28 03:38:26

----- Original Message ----- 
From: "Andreas Huber" <ah2003_at_[hidden]>

> E. Gladyshev wrote:
> > From: "Andreas Huber" <ah2003_at_[hidden]>
> > [...]
> >> Unfortunately, all FSM standards/publications I know are absolutely
> >> silent on error handling.
> >>
> >
> > I can understand why.
> > If you are referring to "error" as something unexpected,
> > then it is out of the state machine realm.
>
> If the errors were unexpected it would make little sense to handle them in
> the state machine, right?

Right.

> > The state machine mantra is complete behavioral determinism.
> > If "error" is an expected condition, then it is just a normal
> > event that is part of the state machine design.
>
> When an entry action fails, you have the problem that the state machine is
> unstable because it would be a bad idea to just continue to enter other
> (inner) states (see Rationale). Since it is non-trivial to define what to
do
> in such a situation, I think it is unfortunate that all these standards
are
> silent on error handling. They implicitly force you define all your entry
> and transition actions in a way so that they can never fail.

Agree. All these standards imply that by definition nothing
*unpredictable* can happen to the state machine.

Eugene