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Re: % in URIs

From: Graham Klyne <gk@ninebynine.org>
Date: Wed, 03 Sep 2003 09:21:05 +0100
Message-Id: <>
To: Jeremy Carroll <jjc@hplb.hpl.hp.com>, RDFCore Working Group <w3c-rdfcore-wg@w3.org>
Cc: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>

Hmmm... that was a pretty obtuse collection of references,
but I finally found something in there...

The text you use seems to come from:
specifically, the description of mapping IRIs to URIs, which would seem
to be a similar context to what is intended here.

In this context, I think it is assumed that the Unicode URI has already been
formed in a way that the only occurrence of '%' is as part of an escape
sequence.  So in this respect, I now think the current text is correct.

But, this point is demonstrated to be prone to misunderstanding, and I think
a brief note of explanation is in order, e.g.:
'%' is excluded from the list of disallowed octets that must be escaped,
because it may appear in a URI only to introduce an escape sequence,
so an additional application of escaping here would be incorrect.


At 18:04 02/09/03 +0100, Jeremy Carroll wrote:

>Graham (offlist) wrote:
> > ACTION: 2003-08-29#3 gk check CONCEPTS 6.4 wrt details of URI and "%"
> >
> > cf.  pfps comment on sectin 6.4 of concepts
> >   http://lists.w3.org/Archives/Public/www-rdf-comments/2003JulSep/0282.html
> > [[
> > It appears to me that RDF Concepts does not require % to be %-escaped in
> > RDF URI references (Section 6.4).  Surely this is a bug.
> > ]]
> >
> > So, checking:
> >
> > 
> http://www.w3.org/2001/sw/RDFCore/TR/WD-rdf-concepts-20030117/#section-Graph-URIref 
> >
> > [[
> > The disallowed octets that must be %-escaped include all those that do
> > not correspond to US-ASCII characters, and the excluded characters
> > listed in Section 2.4 of [URI], except for the number sign (#), percent
> > sign (%), and the square bracket characters re-allowed in [RFC-2732].
> > ]]
> >
> > I think PFPS is right, and that ", the percent sign (%)" should be
> > deleted from the above paragraph.
>I tried to take the text from the usual suspects and minimize the 
>divergence between different W3C specs.
>cf in particular
>which links to
>None of these %-escape %.
>I believe that w3c-i18n-ig@w3.org and uri@w3.org may be appropriate forums 
>for discussion of this issue.
>I am unwilling to make a change before the 5th September publication.
>Nor would I be happy with a change that is opposed by a consensus in the 
>above forums.
>I am not yet convinced that this materially affects RDF since we *never* 
>require the escaping to actually be performed, it is merely a theoretical 
>exercise that defines a set of strings. I believe that the set of strings 
>is the same whether or not % is itself escaped.

Graham Klyne
Received on Wednesday, 3 September 2003 05:52:27 UTC

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