[Sigia-l] Error Prevantion Heuristic (slightly OT)

[Richard_Dalton at vanguard.com]

Listera writes:
> > This is a slightly rhetorical question because I know you'd never do 
that - so
> > I guess my question is "why?" - what heuristic or principle of "good 
design"
> > is overriding the "prevent errors" one in this instance?
>
> It depends on the context.
>
> If this field entry is a (very) occasional task, entry-followed-by-alert 
may
> be acceptable. If, however, it's a repeated task (done, for example, by 
data
> entry operators), it won't be acceptable to have to dismiss alert boxes
> continuously within the workflow.
>
> Strictly speaking, you are not actually *preventing* the user from 
pressing
> the '6' key, you're post-processing it to divert it to either an alert 
or,
> what's essentially, a 'clear keystroke'.
>
> 'Preventing' would be three separate popup choice lists for each digit, 
with
> the first one containing only 1,2,3,4,5.
>
> 'Rules' without context are meant to annoy people who care.

Thanks - here is some more context and a more concrete example.

Lets say its a banking site and a user can see a couple of individual 
checking
accounts and a joint checking account. The user wants to move $1000 from 
one
individual checking account to the joint account, however, because of 
technical
constraints or business rules on the website he can only move between the 
individual
checking accounts - should the system prevent him from selecting what he 
wants to
select - or allow him to select what he wants and give him a message 
telling him
he can't do it on the web (and why) and explaining the other options for 
how he
might do it?

 - Richard Dalton