Re: [precis] names and usernames

John C Klensin <> Sun, 12 February 2017 23:43 UTC

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Date: Sun, 12 Feb 2017 18:43:24 -0500
From: John C Klensin <>
To: Peter Saint-Andre <>,
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Subject: Re: [precis] names and usernames
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Just to be clear to you and the WG, I don't have a strong
opinion about what decision the WG should make in these cases,
but I do believe the decision must be explicit and the result of
discussion, not something that happens as an accident without
knowledge of the relevant cases.


--On Sunday, February 12, 2017 16:29 -0700 Peter Saint-Andre
<> wrote:

> John Klensin has brought to my attention that it is currently
> impossible to represent some people's names in PRECIS
> usernames because some of the relevant Unicode code points are
> disallowed by the IdentifierClass defined in RFC 7564 (and
> thus by the UsernameCaseMapped and UsernameCasePreserved
> profiles defined in RFC 7613).
> First, RFC 7564 disallows "default ignorable" code points in
> the IdentifierClass. However, as I understand it some of these
> code points are need to represent characters in names that
> might be desirable to people living within communities that
> use Indic script and eastern Arabic script (e.g., Persian and
> writing systems derived from Persian). In particular, the
> Unicode Standard specifies that ZWJ and ZWNJ are "default
> ignorable" and it seems that these code points are especially
> important in this context.
> Second, apparently some Chinese family names are typically
> written (especially outside the People's Republic of China)
> using characters that the Unicode Consortium assigns to
> non-BMP code points, or assigns in the BMP but as
> compatibility decomposable characters (and thus disallowed by
> RFC 7564 in the IdentifierClass).
> I'm not sure whether we can solve these problems
> (internationalization is messy and we've never tried to
> guarantee that any particular name or preferred string could
> be represented in PRECIS usernames), but input from people
> with a deeper understanding of these issues would be
> appreciated. I have attempted to reach out to relevant
> experts, and will report back to this list with any findings.
> In the meantime, I plan to submit revised I-Ds addressing
> other issues with the PRECIS specifications sometime this
> evening.
> Peter
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