Re: SHOULD vs MUST

Fred Baker <fred@cisco.com> Wed, 25 June 2008 09:37 UTC

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From: Fred Baker <fred@cisco.com>
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Subject: Re: SHOULD vs MUST
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On Jun 25, 2008, at 5:28 AM, Frank Ellermann wrote:

>> A SHOULD X unless Y essentially means "SHOULD (X or Y)"
>
> I'd read it as "do X, but if you have a very good excuse
> not doing X might do.  One known very good excuse is Y."

That is more or less my definition of "should". I say something "must"  
be so when I can tell you an operational failure that would or could  
happen if it isn't. If I would like to say "must" but can think of a  
case in which it would not be appropriate I say "should", and am  
saying that if it is not so in someone's implementation they should be  
prepared to say what their reason was.
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