Need reference to good ABNF for \uXXXX syntax

Markus Scherer at
Wed Apr 14 12:43:51 CDT 2021

Hi Doug,

On Wed, Apr 14, 2021 at 6:45 AM Doug Ewell via Unicode <unicode at>

> Is anyone aware of an existing RFC or other specification that includes
> complete, correct, and clear ABNF for Unicode escape sequences using the
> UTF-16 encoding scheme?
> ...
> "Correct" implies, for instance, that the ABNF excludes unpaired
> surrogates.

I was looking for something, but all I can find is either loose about
surrogates (e.g., Java
<>), or deals
in code points rather than UTF-16 code units.

Can you say why you want/need strict 16-bit escapes for well-formed UTF-16
code units, rather than what others are doing?

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