----- Original Message ----- 
From: "Andreas Huber" <ah2003@[...].net> 

>  E. Gladyshev wrote:
>  > From: "Andreas Huber" <ah2003@[...].net>
>  > [...]
>  >> 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

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