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ACTION-295: Should v. Must

From: David Wainberg <david@networkadvertising.org>
Date: Wed, 17 Oct 2012 16:10:37 -0400
Message-ID: <507F10BD.8030201@networkadvertising.org>
To: "public-tracking@w3.org" <public-tracking@w3.org>
Hi all,

 From our call today, it seemed as if we are agreed that SHOULD=MUST. If 
that's the case, let's replace all the SHOULDs with MUSTs in order to 
avoid ambiguity. Otherwise, if we use both, the intent is ambiguous and 
implementers will be confused and sad.

If it is not the case that we view them as equivalent, then as Berin 
suggested, we must get clear on what is our intent when using a SHOULD 
instead of a MUST. Despite the emphatic statements on the call today 
that it's perfectly clear, it is not so.

 From http://www.ietf.org/rfc/rfc2119.txt, these are the definitions of 
MUST and SHOULD:

MUST   This word, or the terms "REQUIRED" or "SHALL", mean that the
    definition is an absolute requirement of the specification.

SHOULD   This word, or the adjective "RECOMMENDED", mean that there
    may exist valid reasons in particular circumstances to ignore a
    particular item, but the full implications must be understood and
    carefully weighed before choosing a different course.


There is obviously quite a difference between these two. I understand 
how the difference makes sense in a technical specification. However, 
for lawyers who will be interpreting the compliance specification, this 
is guaranteed heartache. What are "valid reasons in particular 
circumstances to ignore" part of the compliance specification? 
Contractual requirements? Cost? Breaks our business model? Don't feel 
like it? Does this translate to a reasonableness standard? In other 
words, does it mean that for a SHOULD requirement, an implementer must 
do it if it is reasonable to do so, but may ignore it otherwise? Does 
that not apply to the whole standard? Or do we mean that MUSTs must be 
done whether reasonable or not? If something in the spec is 
unreasonable, then why is it in the spec?

Best,

David
Received on Wednesday, 17 October 2012 20:11:07 UTC

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