status of Programming by Contract (PEP 316)?

Steve Holden steve at
Sat Sep 1 03:45:01 CEST 2007

Jorge Godoy wrote:
> Russ wrote:
>> Alex, I think you are missing the point. Yes, I'm sure that web
>> searches are critical to
>> Google's mission and commercial success. But the point is that a few
>> subtle bugs cannot
>> destroy Google. If your search engines and associated systems have
>> bugs, you fix them
>> (or simply tolerate them) and continue on. And if a user does not get
>> the results he wants,
>> he isn't likely to die over it -- or even care much.
> But if this pattern of not getting wanted results is common, then the user
> will migrate to alternative search engines and this will *kill* the
> business.  Wrong results won't impact ONE search, but many will impact the
> company business and will be part of the recipe to take it out of business. 
>> Online financial transactions are another matter altogether, of
>> course. User won't die, but
>> they will get very irate if they lose money. But I don't think that's
>> what you are talking about
>> here.
> Lets make someone loose his job and have all his money commitments
> compromised because of this money lost and we might be talking about people
> taking their lives.
> Again, this isn't 100% sure to happen, but it *can* happen.  
> As it happens with a peacemaker: the user won't die if his heart skips one
> beat, but start skipping a series of them and you're incurring in serious
> problems.
> Just because the result isn't immediate it doesn't mean it isn't critical.
We probably need to distinguish between "mission-critical", where a 
program has to work reliably for an organization to meet its goals, and 
"safety-critical" where people die or get hurt if the program misbehaves.

The latter are the ones where you need to employ all possible techniques 
to avoid all possible failure modes.

Steve Holden        +1 571 484 6266   +1 800 494 3119
Holden Web LLC/Ltd 
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