Re: [Ltru] RE: Remove extlang from ABNF? (Was: summary of recommendations coming out of this week's teleconf

>> From: Stephane Bortzmeyer [mailto:bortzmeyer@nic.fr]
>
>
>> > remove extlang from the ABNF.
>>
>> Warning, it means that tags which were well-formed in RFC 4646 (but
>> not valid since no extlang was registered) won't be well-formed
>> anymore. Isn't a violation of the stability principle? (Yes, the
>> "extlang" production in RFC 4646 was marked as "reserved for future
>> use" but it was legal nevertheless.)
>
> Correct. Since there have never been registered extlang subtags, there
> might be parsers that allow for it but there should not be any tags that
> include them. If some such tags are out there in the wild, they would be
> well-formed but not valid in 4646, and neither well-formed nor valid in
> 4646bis (under this proposal).

Note that this change has consequences not only for implementations, but
also for specifications citing BCP 47 / RFC 4646. To give an example, see
e.g.
http://www.w3.org/Bugs/Public/show_bug.cgi?id=3079#c2
this is a comment on a W3C draft of "XML Schema 1.1 , part 2 - datatypes",
about the "language" data type. We were saying
"We would like to propose that you use the ABNF defined in RFC 4646. This
ABNF is stable."

So if extlang is not legal anymore, we will need to change that comment.

Felix

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