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Re: Comments on GRDDL (using 3rd-party XML schemas with GRDDL) [OK?]

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Thu, 19 Jul 2007 12:22:26 -0400
Message-ID: <469F8FC2.5070804@ibiblio.org>
To: Jonathan Robie <jonathan.robie@redhat.com>
Cc: Dan Connolly <connolly@w3.org>, "C. M. Sperberg-McQueen" <cmsmcq@acm.org>, Jim Melton <jim.melton@acm.org>, Andrew Eisenberg <andrew.eisenberg@us.ibm.com>, public-grddl-comments@w3.org, w3c-xsl-query@w3.org

Jonathan Robie wrote:
> Let me ask a few questions to try to understand the basic design.
> As I read http://www.w3.org/2004/01/rdxh/spec#ns-bind, I have two
> choices: I can either associate a transformation with individual
> documents, or with all documents for a given namespace. If I want to
> do the latter, I can only do so if I am able to create a resource at
> the address corresponding to the namespace URL. Did I get that right?
Create, or modify. Or ask the owner to modify. In that way, GRDDL is
self-describing, as one can "follow-your-nose" from the individual
document or namespace document to a transformation.
> Does the term "3rd-party XML schemas" have a technical meaning, or
> could we change the title to "Using XML Schemas with GRDDL" without
> changing the meaning
> (I'm sure you're aware that most XML Schemas in use today are not
> available using HTTP and the associated namespace URL.)
> Are you avoiding the XML Schema mechanisms because you want to avoid
> XML Schema processing, or because you need an explicit mechanism to
> specify the relationship between a namespace and the associated
> schema, or for some other reason?
As said earlier, XML Schema processing is not needed by GRDDL, as all
GRDDL needs is a link to a transformation, as given by the object of the
RDF  property
Therefore, we are not avoiding XML Schema processing because it is not
needed by GRDDL.

 This RDF statement may be embedded in XHTML, XML Schema, RDF Schema, -
quite a lot of things which we hope cover at least some of the things
people might put in namespace URIs. We are aware that schemas are often
put other places, but some people do sometimes put XML Schemas at
namespace URIs.

> What's important to me is that the "interesting" semantics of a
> document depend on who is processing the document. Suppose I'm a
> regulatory agency or the Department of Homeland Security and I am
> looking for patterns in FIX documents or SOAP documents, which are
> created by people completely ignorant of what I am doing, and which
> may be in a stream. I can't easily modify those documents. I don't own
> the namespace. What do I do?
You can always use an external GRDDL transformation without a
GRDDL-aware agent. This is in our primer document [2], along with our
explanation about why this is useful and some common-sense observations
about why one should be careful about this, as
"http://www.w3.org/TR/grddl-primer/ . Again, GRDDL is not the only way
to get RDF out of XML, it is one way.

> Jonathan
> C. M. Sperberg-McQueen wrote:
>> On 18 Jul 2007, at 16:08 , Harry Halpin wrote:
>>> An aside, although the official response will come from Dan himself.
>>> The reason GRDDL does not use third-party schemas is because it
>>> already has a mechanism (for both XHTML and XML) for pointing to
>>> third-party transformations. Since the only reason GRDDL uses a
>>> schema at the namespace URI is to find a transformation (as it uses
>>> no other part of the schema), it seems reasonable to assume that if
>>> a schema is somewhere else rather than at a namespace URI, then the
>>> user can simply directly point to the transformation given by the
>>> "third-party" schema. This keeps indirection to minimum.
>> So if I have a few thousand, or a few hundred thousand, documents
>> in the same vocabulary, and use a schema for that vocabulary which
>> is not at the namespace name but which is accessible to my processes,
>> the advice of the GRDDL group is not to document the transformation
>> in the schema document, but to edit each document and add an
>> explicit link to the GRDDL transformation for that vocabulary?
>> Given that the semantics are associated with the vocabulary,
>> and the annotations for the vocabulary are documented in the
>> schema document I use -- and given that there's no particular
>> technical difficulty involved here, that I can see -- why would
>> I as a document owner want to incur that kind of cost and
>> introduce that kind of redundancy?
>> --C. M. Sperberg-McQueen


Harry Halpin,  University of Edinburgh 
http://www.ibiblio.org/hhalpin 6B522426
Received on Monday, 20 August 2007 01:36:32 UTC

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