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Re: Possible solutions for ISSUE 97

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Thu, 20 Mar 2008 10:16:54 +0000
Message-ID: <a707f8300803200316n1ea57133x22403a6c8203bb87@mail.gmail.com>
To: "Ben Adida" <ben@adida.net>
Cc: public-rdf-in-xhtml-tf@w3.org

Hi Ben,

There is only one *exclusive* canonical form of your XML, and that is this:

  <div xmlns="http://www.w3.org/1999/xhtml">
    foo <b>bar</b>

I assume what you're trying to say is that (a) if we are entitled to
serialise this 'abstract' value in two different ways, then (b) what
difference does it make what we use as the abstract version, meaning
that (c) we don't need to use canonicalisation to create XML literals.

First, I don't agree that there are many different serialisations
possible of the same graph. Given the exclusive canonicialised form I
just gave, what is it that would add the second namespace declaration?
I.e., what part of the process of moving from abstract graph to
concrete serialisation would alter the form of the string of
characters that represent the abstract data.

Second, if there was this scope for 'wiggle room'--i.e., that we could
unilaterally decide whether to canonicalise or not--then what would be
the point of exclusive canonicalisation in RDF in the first place?

I think the nature of XML literals and the fact that they are based on
XML that has been exclusively canonicalised leaves very little room to
manoeuvre. If we want to do XML literals, we have no choice but to do
them properly. The alternative is to accept that the data we are
dealing with is *not* generic XML, but is actually XHTML, and process
it accordingly. (I'll outline that in a separate post.)



On 20/03/2008, Ben  <ben@adida.net> wrote:
> Mark Birbeck wrote:
>  > So however people reply to this view-point, they need to make some
>  > reference to RDF Concepts, and say why my interpretation *of that* is
>  > wrong.
> I think you're framing the problem incorrectly and torturing yourself
>  into more complexity than needed.
>  But instead of writing another massive email, let me try to identify
>  where, in the logical flow, we disagree with one another.
>  In your flow, here's where I disagree:
>  >   (1) we run the RDFa parser on an input document,
>  >   (*) the output of the RDFa parser is RDF
>  >   (2) we take the output of the parser and stuff it into a triple store,
>  >   (3) we SPARQL against the triple store.
> Step (*) is imprecise, in my opinion; it mixes abstract and concrete.
>  The output of an RDFa parser is, IMO, *a serialization of an RDF graph*.
>  That is the key difference, because the "RDF Concepts" definition of
>  XMLLiteral applies to the abstract graph, not to all of the graph's
>  valid serializations.
>  Now, help me understand where you disagree with my reasoning. Here are
>  two RDF N3 *serializations*:
>  <> dc:title
>  "<div xmlns="http://www.w3.org/1999/xhtml">
>    foo <b xmlns="http://www.w3.org/1999/xhtml">bar</b>
>  </div>"^^rdf:XMLLiteral
>  and
>  <> dc:title
>  "<div xmlns="http://www.w3.org/1999/xhtml">
>    foo <b>bar</b>
>  </div>"^^rdf:XMLLiteral
>  If I'm reading the XMLLiteral canonicalization process correctly, I
>  believe that the two examples above are serializations of the same RDF
>  graph.
>  Do you agree? If not, why not?
>  -Ben

  Mark Birbeck

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Received on Thursday, 20 March 2008 10:17:31 UTC

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