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Re: Postel's law, exceptions

• To: Rich Salz <rsalz@d...>
• Subject: Re: Postel's law, exceptions
• From: Elliotte Rusty Harold <elharo@m...>
• Date: Tue, 13 Jan 2004 23:54:32 -0500
• Cc: "'xml-dev@l... '" <xml-dev@l...>
• In-reply-to: <Pine.LNX.4.44L0.0401132032500.11058-100000@s...>
• References: <Pine.LNX.4.44L0.0401132032500.11058-100000@s...>

At 8:34 PM -0500 1/13/04, Rich Salz wrote:
>The thing "they" all seem to miss about the Postel quote, was that it was
>written as part of a specification, and referred to that spec.  When
>there's "wiggle room" in the spec, be liberal in what you accept, and
>conservative in what you implement.  Where there's no ambiguity (over
>there, in the box), the rule doesn't apply.
>

The original statement of the law comes from section 2.10 of RFC 793 
which can be found here:

http://www.ibiblio.org/pub/docs/rfc/rfc793.txt

The actual quote is:

   TCP implementations will follow a general principle of robustness:  be
   conservative in what you do, be liberal in what you accept from
   others.

Clearly at the the time Postel meant it to apply only to TCP. It's 
not obvious to me that he was referring only to spec interpretation 
here. Perhaps that becomes clear when this is read in the context of 
the whole TCP spec. But whether he meant it or not, the weak form of 
Postels' law is a lot more palatable to me than the strong form.
-- 

   Elliotte Rusty Harold
   elharo@m...
   Effective XML (Addison-Wesley, 2003)
   http://www.cafeconleche.org/books/effectivexml            
   http://www.amazon.com/exec/obidos/ISBN%3D0321150406/ref%3Dnosim/cafeaulaitA 

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