Re: [precis] Ambiguity in specification of case mapping in RFC 7613 and draft-ietf-precis-nickname

Peter Saint-Andre <peter@andyet.net> Wed, 04 November 2015 15:37 UTC

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To: John C Klensin <john-ietf@jck.com>, Tom Worster <fsb@thefsb.org>, Alexey Melnikov <Alexey.Melnikov@isode.com>
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From: Peter Saint-Andre <peter@andyet.net>
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Date: Wed, 4 Nov 2015 08:37:03 -0700
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Subject: Re: [precis] Ambiguity in specification of case mapping in RFC 7613 and draft-ietf-precis-nickname
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On 11/3/15 6:42 AM, John C Klensin wrote:
>
>
> --On Tuesday, November 03, 2015 08:16 -0500 Tom Worster
> <fsb@thefsb.org> wrote:
>
>> The informative sentence in 2.1 Rule 3:
>>
>>      "The primary result of doing so is that uppercase
>> characters are     mapped to lowercase characters."
>>
>> is good but I think it's worth spending a few more words to
>> spell out that "primary" implies exceptions.
>>
>>      "While the primary result is that uppercase characters are
>> mapped to     lowercase characters, there are exceptions."
>>
>> It might nudge a few fore implementers to understand that
>> toLowerCase() isn't the right thing.
>
> But Tom, for many purposes, forms, and language-script
> combinations, toLowerCase() is _exactly_ the right thing.  For
> others, if one adopts the principle of doing no harm, whether
> toLowerCase() or toCaseFold() are likely to do less harm depends
> on some rather subtle issues including the perspective from
> which "harm" is viewed.
>
> I think one could more accurately restate your comment above as
> "... to understand that toLowerCase() is sometimes not the right
> thing and that sometimes toCaseFold() is sometimes not the right
> thing either.
>
> I could take a shot at a paragraph explaining that if it is what
> people want.  Otherwise, I'd be very careful about getting
> further into that space than the present text goes.  Personally,
> I think the text is still dancing around the issue too much,
> rather than addressing it, but I may be in the rough.

That may be. We could simply remove the offending sentence:

OLD

    3.  Case Mapping Rule: Unicode Default Case Folding MUST be applied,
        as defined in the Unicode Standard [Unicode] (at the time of this
        writing, the algorithm is specified in Chapter 3 of
        [Unicode7.0]).  The primary result of doing so is that uppercase
        characters are mapped to lowercase characters.  In applications
        that prohibit conflicting nicknames, this rule helps to reduce
        the possibility of confusion by ensuring that nicknames differing
        only by case (e.g., "stpeter" vs. "StPeter") would not be
        presented to a human user at the same time.

NEW


    3.  Case Mapping Rule: Unicode Default Case Folding MUST be applied,
        as defined in the Unicode Standard [Unicode] (at the time of this
        writing, the algorithm is specified in Chapter 3 of
        [Unicode7.0]).  In applications that prohibit conflicting
        nicknames, this rule helps to reduce the possibility of
        confusion by ensuring that nicknames differing only by case
        (e.g., "stpeter" vs. "StPeter") would not be presented to a
        human user at the same time.

If we do that, we're no longer dancing around issues.

Peter