Re: [Ltru] [Technical Errata Reported] RFC5646 (5457)

"Phillips, Addison" <> Sun, 12 August 2018 23:03 UTC

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From: "Phillips, Addison" <>
To: John Cowan <>, RFC Errata System <>
CC: "" <>, "" <>, "" <>, "" <>, Alexey Melnikov <>, "" <>, "" <>, "" <>
Thread-Topic: [Ltru] [Technical Errata Reported] RFC5646 (5457)
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Date: Sun, 12 Aug 2018 23:03:05 +0000
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Subject: Re: [Ltru] [Technical Errata Reported] RFC5646 (5457)
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Hi John and Peter,

“zh-min-nan” is grandfathered and thus valid because it is in that list. It doesn’t have two extlangs, even though it looks like it does. Grandfathered tags are exempt from the other rules.

I think the Peter has a point. The “well-formed” rules mirror the ABNF and the “valid” rules were meant to mirror the ABNF plus the registry. There was some effort expended to make the validity rules “forward compatible” with future potential changes to BCP47. Hence in 4646 days they allowed for future use of extlangs (when point 4 said you must not use extlangs now but that they were reserved). When extlangs came in during 5646 we ruled out the second and third extlang in point 4 but not in the ABNF. Since we say the second and third extlang can never ever be valid, the validity rules should reflect that.


Addison Phillips
Principal SDE, I18N Architect (Amazon)
Chair (W3C I18N WG)

Internationalization is not a feature.
It is an architecture.

From: Ltru [] On Behalf Of John Cowan
Sent: Monday, August 13, 2018 4:33 AM
To: RFC Errata System <>
Cc:;;;; Alexey Melnikov <>fm>;;;
Subject: Re: [Ltru] [Technical Errata Reported] RFC5646 (5457)

On Sun, Aug 12, 2018 at 2:28 PM, RFC Errata System <<>> wrote:

Sec. 2.2.2 contains an additional validity requirement (point 4): the existence of no more than one extended language subtag.  This is not reflected in the definition of validity given in sec. 2.2.9 of the RFC.

It seems to me that it's 2.2.2  rather than 2.2.9 that's at fault.  2.2.2 says:

       That is, the second and third extended language

       subtag positions in a language tag are permanently reserved and

       tags that include those subtags in that position are, and will

       always remain, invalid.

However, the grandfathered tag "zh-min-nan" is valid by the definition in 2.2.9 even though it has a second extended language subtag.. So since the above sentence is not normative (it merely explains what is believed to be a consequence of the preceding statements), it should be removed.

In the alternative, we can simply not worry about it:

The Tract produced an immense sensation, for it seemed to be a deadly and treacherous blow aimed at the very heart of the Church of England. Deadly it certainly was, but it was not so treacherous as at first sight appeared. The members of the English Church had ingenuously imagined up to that moment that it was possible to contain in a frame of words the subtle essence of their complicated doctrinal system, involving the mysteries of the Eternal and the Infinite on the one hand, and the elaborate adjustments of temporal government on the other. They did not understand that verbal definitions in such a case will only perform their functions so long as there is no dispute about the matters which they are intended to define : that is to say, so long as there is no need for them. For generations this had been the case with the Thirty-nine Articles. Their drift was clear enough ; and no body bothered over their exact meaning. But directly some one found it important to give them a new and untraditional interpretation, it appeared that they were a mass of ambiguity, and might be twisted into meaning very nearly anything that anybody liked. Steady-going churchmen were appalled and outraged when they saw Newman, in Tract No. 90, performing this operation. But, after all, he was only taking the Church of England at its v/ord. And indeed, since Newman showed the way, the operation has become so exceedingly common that the most steady-going church- man hardly raises an eyebrow at it now.

--Lytton Strachey, Eminent Victorians (emphasis added)