In article <[email protected]> you write:
>-=-=-=-=-=-
>
>On Mon 2019-01-14 18:09:41 -0500, John R Levine wrote:
>> On Mon, 14 Jan 2019, Daniel Kahn Gillmor wrote:
>>> On Mon 2019-01-14 16:43:15 -0500, John Levine wrote:
>>>> To show that you read it, please include the first word in the text
>>>> on page 50 of RFC 5321 in your reply.
>>>
>>> I'm sorry to spoil it for everyone that the word is "The" :P
>>
>> Sigh.  Nope.
>
>Maybe you're reading a different RFC 5321 than i am.

No, I just can't count.  But you knew that.

>I do observe that in the presence of a single parenthetical aside
>between the mandatory part of the BY clause and the next stated clause,
>it's pretty hard to see how an interpreter can distinguish whether the
>contents of the parenthetical is a TCP-info (part of the BY clause) or a
>Comment (not part of the BY clause), particularly if it matches the ABNF
>for TCP-Info.  That makes interpretation potentially ambiguous in the
>most perverse corner cases.

ABNF does not have to provide an unambigous parse, which often
confuses people.  You are correct that this could either be a TCP-info
or a CFWS comment:

> "(Postfix [19.01.14.23])"
>
>Probably fine to interpret it as a a TCP-info since it matches the ABNF,
>but it's still a little weird that the ambiguity can exist.

There's a lot of places where you need to use contextual clues to
figure out what's going on.  In this example, the fact that Postfix
doesn't contain a dot is a strong clue that it's not a domain name.

R's,
John

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