Re: WGLC: p1 MUSTs

Alex Rousskov <rousskov@measurement-factory.com> Wed, 31 July 2013 21:09 UTC

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Date: Wed, 31 Jul 2013 15:07:06 -0600
From: Alex Rousskov <rousskov@measurement-factory.com>
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Subject: Re: WGLC: p1 MUSTs
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On 07/31/2013 11:48 AM, Roy T. Fielding wrote:
> On Apr 30, 2013, at 11:54 AM, Alex Rousskov wrote:

>>> A sender MUST NOT generate protocol elements that do not match the
>>> grammar defined by the ABNF rules for those protocol elements that
>>> are applicable to the sender's role.

>> The "for those protocol elements..." part should be dropped IMO. A
>> sender MUST NOT generate invalid protocol elements even if they are not
>> applicable to the sender's role. Note that we are talking about
>> _generation_ and not forwarding here.

> That isn't why it is being described. There are ABNF rules that define
> various alternative syntax to be generated based on the role of the
> sender (and, in some cases, based on the role of the recipient).
> It is hard to capture in a small number of words.


Understood. The new wording you linked to below reflects the above
intent better IMO.


>>> If a received protocol element is processed, the recipient MUST be
>>> able to parse any value that would match the ABNF rules
>>
>> "processed" seems too broad because simply buffering a header may be
>> called "processing". "Interpreted" may be better. Or did I miss the
>> definition of "process" that clarifies this?
> 
> Actually, no, simply buffering a header is not called processing.
> "Movement of data or material towards a known goal or end result,
> by passing it through a series of stages or a sequence of actions."
> However, I can rephrase it.

Well, "buffering and printing to the debugging log" if you insist on a
sequence of different actions :-).


>>> If a received protocol element is processed, the recipient MUST be
>>> able to parse any value that would match the ABNF rules for that
>>> protocol element, excluding only those rules not applicable to the
>>> recipient's role.
>>
>> The "excluding only those rules not applicable..." part seems to
>> contradict the "processed" verb. Why would a recipient want to process
>> something inapplicable? Perhaps this is related to the "process" versus
>> "interpreted" issue mentioned above.
> 
> A client does not need to parse syntax that is only sent to servers.
> An origin server does not need to parse syntax that is only sent by
> a server. ...


Sure, but the "a received protocol element is processed" precondition
already excludes those cases. Your focus here was different, and I think
the new wording is better in this aspect as well.


>> the recipient MUST be
>>> able to parse any value that would match the ABNF rules for that
>>> protocol element, excluding only those rules not applicable to the
>>> recipient's role.
>>
>> Please rephrase to avoid double negation in "excluding not applicable".
>> For example: "the recipient MUST be able to parse any value matching the
>> corresponding ABNF protocol element rules applicable to the recipient's
>> role"
> 
> Okay.
> 
> One more attempt at describing the overall conformance requirements
> has been committed to address this part of #484 (and related concerns).
> 
> http://trac.tools.ietf.org/wg/httpbis/trac/changeset/2332


I think that change addresses the above issues.


Thank you,

Alex.