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Re: character encoding in RDF (including some new related issues)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Thu, 06 Nov 2003 14:38:44 -0500 (EST)
Message-Id: <20031106.143844.46611732.pfps@research.bell-labs.com>
To: dave.beckett@bristol.ac.uk
Cc: www-rdf-comments@w3.org

From: Dave Beckett <dave.beckett@bristol.ac.uk>
Subject: Re: character encoding in RDF (including some new related issues)
Date: Thu, 6 Nov 2003 15:25:12 +0000

> On Thu, 06 Nov 2003 08:59:05 -0500 (EST), "Peter F. Patel-Schneider" <pfps@research.bell-labs.com> wrote:
> 
> > From: Dave Beckett <dave.beckett@bristol.ac.uk>
> > Subject: Re: character encoding in RDF
> > Date: Thu, 6 Nov 2003 10:42:33 +0000
> > 
> > > It has been suggested off list that you might be satisfied with the editorial
> > > changes suggesed by Jeremy Carroll in
> > >   http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Nov/0006.html
> > 
> > I view these changes as a variation of the changes I suggested in my
> > initial message on this topic.  These changes do indeed capture the intent
> > of the situation, as opposed to the wording in the current document.
> > 
> ....
> 
> > These changes would indeed provide an acceptable disposition, provided that
> > they are made in all the appropriate places.  I identified Section 6.1.6,
> > 6.1.7, 6.1.8, and 6.1.9 in my initial message; Jeremy only proposes three
> > changes, not including the one for blank node identifiers.  This difference
> > indicates that there should be another effort to identify all the places
> > where this sort of change needs to be made.
> 
> So if we change 6.1.6, 6.1.8 and 6.1.9 as Jeremy outlines that's part
> of an answer - read further on for more.
> 
> We changed the 6.1.7 blank node description from your comments in
> earlier WDs and I haven't seen you mention it in this thread.  I'm
> not proposing any changes there since it already says how the entire
> value MUST match an N-Triples production.

Ah yes.  The ``function'' bit does indeed allow for the necessary escaping
for 6.1.7, so this one does not have to be changed.   I was also mistaken
in identifying 6.1.7 in my initial message on this thread.

> > Upon further analysis, I note that the URI and string-value for attribute
> > events as well as the URI for element events can be placed directly in a
> > triple (as in Section 7.2.11) and so need a similar treatment.  Any grammar
> > action that has a <...> in it probably suffers from this problem.
> > 
> > However, the string-value of attribute events is used in the sections
> > above, so just making a variation of Jeremy's proposed change is
> > insufficient, as it would end up specifying double escaping.  My proposed
> > change would be somewhat better at avoiding double escaping, but it still
> > could be read as requiring double escaping.
> 
> Yes, that seems something we should fix.
> 
> I think the best way to do this would be to as you suggest, remove all
>   <X.URI> <X.string-value>
> in N-Triples actions for X=e, a as elements and attributes and to
> create new accessors for both the element and attribute events
> when used to make URI strings for N-Triples (similar to 6.1.6
> URI Reference Event)
> 
> 
> So, this would add
> 
> [[
>   URI-string-value
> 
> The value is the concatenation of the following in this order "<",
> the escaped value of the *URI* accessor and ">".
> 
> The escaping of the *URI* accessor uses the N-Triples escapes for
> URI references as described in 3.3 URI References.
> ]]
> 
> to both 6.1.2 Element Event and 6.1.4 Attribute Event.

> Read on for further changes
> 
> 
> > Also, I believe that the treatment in the second actions of Section 7.2.11
> > and Section 7.2.21 are insufficient, as they neither check that the type
> > URI is in the form required of a URI in an RDF Graph nor do any escaping.
> > I expect that using a URI Reference Event as an intermediary would both
> > solve all of these problems as well as part of the problem above.
> 
> 
> After the above changes, these could be the consequent changes:
> 
> 7.2.11 
> [[ 
> If there is an attribute a in propertyAttr with a.URI == rdf:type
> then u:=uri(identifier:=resolve(a.string-value))
> and the following triple is added to the graph:
> 
> e.subject.string-value <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> u.string-value . 
> 
> ]]
> 
> 7.2.21
> [[
> If a.URI == rdf:type then u:=uri(identifier:=resolve(a.string-value))
> and the following triple is added to the graph:
> 
> r.string-value <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> u.string-value .
> 
> ]]
> 
> 
> Looking at other changes needed from X.URI to X.URI-string-value
> (anywhere "<"..">" appears in the grammar action without a
> hardcoded URI reference would be changed)
>   7.2.11 <e.URI> and <a.URI>
>   7.2.15 <e.URI>
>   7.2.16 <e.URI>
>   7.2.17 <e.URI>
>   7.2.18 <e.URI>
>   7.2.19 <e.URI> twice
>   7.2.21 <e.URI> twice, <a.URI> once

This seems to be the best way of handling this issue. 

> > Further, the wording in 7.2.32 is rather suspect.  What does it mean for a
> > string to represent an RDF URI reference?  
> 
> Amusingly, those words are from the original RDF M&S BNF, updated for
> later notation changes and it might be they aren't needed.
> 
> The choices I see are
>  1 remove the URI-reference term, replacing with string where it was used
>  2 changing the wording to just say "An RDF URI Reference"
>  3 changing the wording to just say "A Unicode string"
> 
> I'm favouring #2 since it is handy to see where in the grammar where
> we know RDF URI references appear and we already enforce elsewhere
> (in URI Reference Event 6.1.6) that those Unicode strings must be RDF
> URI References.

I agree that #2 is the best way to proceed here.

[The related issue with URI references is the subject of a separate response.]

> > > Thanks
> > > 
> > > Dave
> > 
> > I await a revised, fully-worked-out proposal for the actual changes.
> 
> You've raised some more things each time for us to answer so you'll
> have to let me know.

Umm, I think that something is backward here.  My understanding of the
review process is that I, as a reviewer, point out problems with the
document(s).  You, as an RDF Core WG member, make changes to the documents,
which may or may not be satisfactory to me.  All the rest is simply being
helpful - I make suggestions as to what might fix the problems I point out;
you ask in advance whether a proposed partial solution to a problem might
be satisfactory.  

In light of this process, then, my response was indicating that I thought
that the general approach that you suggest was a good direction in which to
go, but that I am not willing to give final approval until I see the final
changes.

> Dave

Peter F. Patel-Schneider
Bell Labs Research
Received on Thursday, 6 November 2003 14:39:44 GMT

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