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

John C Klensin <john-ietf@jck.com> Tue, 03 November 2015 13:42 UTC

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Date: Tue, 03 Nov 2015 08:42:09 -0500
From: John C Klensin <john-ietf@jck.com>
To: Tom Worster <fsb@thefsb.org>, Peter Saint-Andre <peter@andyet.net>, Alexey Melnikov <Alexey.Melnikov@isode.com>
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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 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.

    john