Re: [apps-discuss] Review of draft-ietf-appsawg-file-scheme

John C Klensin <john-ietf@jck.com> Sun, 08 May 2016 16:26 UTC

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Date: Sun, 08 May 2016 12:26:41 -0400
From: John C Klensin <john-ietf@jck.com>
To: Julian Reschke <julian.reschke@gmx.de>, Matthew Kerwin <matthew@kerwin.net.au>
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Cc: draft-ietf-appsawg-file-scheme@ietf.org, IETF Apps Discuss <apps-discuss@ietf.org>
Subject: Re: [apps-discuss] Review of draft-ietf-appsawg-file-scheme
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--On Saturday, May 07, 2016 11:31 +0200 Julian Reschke
<julian.reschke@gmx.de> wrote:

>> Care must be taken to avoid issues resulting from aliasing
>> from mismatched encodings or Unicode equivalences.
>> ""
> 
> That can't hurt.
> 
> I wonder whether we can say something useful about how to map
> Unicode code points into the file URI (that is, before
> percent-encoding the UTF-8 octets). Is it a good idea to apply
> unicode normalization at this step? (I don't know but maybe
> others do?)

The developing conventional wisdom outside the IETF is to not
bother (and run the risk of normalization losing information or
causing other problems) but to save normalization for the actual
point at which the URI or other identifier is interpreted.  In
the particular case of "file" that might be particularly
important since some systems prefer different normalization
forms and have different restrictions.

Note that is not necessarily advice, just a report.

   john