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

From: Jonathan Robie <jonathan.robie@redhat.com>
Date: Wed, 25 Jul 2007 16:33:15 -0400
Message-ID: <46A7B38B.5080000@redhat.com>
To: Harry Halpin <hhalpin@ibiblio.org>
CC: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>, Dan Connolly <connolly@w3.org>, Andrew Eisenberg <andrew.eisenberg@us.ibm.com>, public-grddl-comments@w3.org, w3c-xsl-query@w3.org

Harry Halpin wrote:
> C. M. Sperberg-McQueen wrote:
>   
>> On 24 Jul 2007, at 10:38 , Harry Halpin wrote:
>>     
>>> ...
>>> I understand that's a perfectly sensible use-case, but not for GRDDL as
>>> it stands. There is a technical difficulty: Since the schema is not at
>>> the namespace document and not marked up in the document, how would the
>>> GRDDL processor ever discover your schema annotations by "following its
>>> nose" from the source document?
>>>       
>> I imagine it happening the same way it happens for schema
>> processors.  Different schema processors do it differently;
>> possible mechanisms include invocation-time parameters,
>> catalogs, local repositories, well-known locations,
>> dereferencing the namespace name, and of course hints in
>> the document.
>>
>> From this discussion I understand that if a GRDDL processor
>> allows me to specify where to find schema documents I'd like
>> to use, then that processor doesn't conform to the GRDDL
>> spec.  That seems a shame to me.
>>     
> We do not forbid GRDDL agents from allowing "local policy" to provide
> additional parameters for GRDDL processing - in fact, we go through
> great pains in the specification and the test-suite to allow local
> policy to determine certain types of processing as regards security and
> processing, and it is under this rubric that one could imagine a local
> policy specifying that all documents of vocabulary X use transformation
> associated with a schema at the non-namespace document location Y
> through an additional parameter. However, as GRDDL is an intentionally
> lightweight specification that purposively avoided adding additional
> required parameters, we did not *require* GRDDL-aware agents to have
> this parameter, as GRDDL-aware agents may have *no parameters*.
>
> So,  a GRDDL-aware agent could have additional parameters specifying
> schemas and transformations locations in accordance with local policy,
> and *still be a conformant GRDDL specification* as long as it passes our
> test-suite. However, we do not specify this sort of behavior in out
> test-suite, as it would be local policy.
>   

This may point to a solution. The W3C XML Schema spec allows 
implementations great freedom in how they do - or do not - locate a 
schema for a given namespace used in an XML document. This is specified 
in *http://www.w3.org/TR/xmlschema-1/#schema_reference.

A GRDDL-aware agent could either dereference the URL directly to see if 
there is a schema there, or use any other means at its disposal to find 
a schema that governs a namespace used in a document. From what you say 
above, I don't think this would actually change the definition of GRDDL, 
but saying this would be helpful to those who use W3C XML Schema. Of 
course, you can't require GRDDL processors to use any particular 
strategy, or insist that they actually find a schema, but the XML Schema 
specification doesn't do that either.

If you said this in the spec, I think I personally would be satisified. 
(I speak neither for Michael nor for the Working Group.)

Jonathan
*
Received on Wednesday, 25 July 2007 20:34:21 GMT

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