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RE: issue-dbooth-10: Does an XML namespace necessarily imply semantics?

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Fri, 25 May 2007 19:34:42 -0400 (EDT)
To: "Booth, David (HP Software - Boston)" <dbooth@hp.com>
Cc: public-grddl-comments@w3.org, Jeremy Carroll <jjc@hpl.hp.com>, "McBride, Brian" <brian.mcbride@hp.com>
Message-ID: <Pine.LNX.4.64.0705251911570.10977@tribal.metalab.unc.edu>

I am happy to (about to go on 2 week vacation, but when I return) add 
warning text to primer if it is thought necessary. If so, David, please 
provide the exact text. Does this satisfy this comment?

Furthermore, as regards the spec and GRDDL itself, it seems to implicit in 
the very  definition of GRDDL that by using a namespace document.

"Likewise, by specifying a GRDDL namespace transformation or profile 
transformation, the creator of that namespace or profile states that the 
transformation will provide a faithful RDF rendition of a class of source 
documents which relate to that namespace or profile. A namespace document 
or a profile document also provide a means for their authors to explain in 
prose the purpose of the transformation or any policy statements." [1]

Providing a faithful rendition is another way of hitting upon the same 
issue regarding the use of an XML Vocabulary, as in the  case of Ralph he 
would not be providing a faithful rendition.

Note that furthermore the TAG has made this decision re the root node, not 
all the nodes. Thus, this does support our decision to postpone any 
issues about applying GRDDL transformations to XPath nodes not 
specified on on the root node.


ware - Boston) wrote:

> While I was preparing the message below, DanC replied to Jeremy's query
> on this, saying that the WG and TAG had considered this question, and an
> XML namespace on the root element *does* imply a certain set of
> semantics:
> http://lists.w3.org/Archives/Public/public-grddl-wg/2007May/0071.html
> FWIW, I agree with the TAG's position on this, so the only remaining
> question for the GRDDL WG is whether the GRDDL spec should include a
> warning about this.  Actually, I think the best approach might be to
> include a brief explanation of this in the GRDDL primer.
> David Booth, Ph.D.
> HP Software
> +1 617 629 8881 office  |  dbooth@hp.com
> http://www.hp.com/go/software
>> -----Original Message-----
>> From: public-grddl-comments-request@w3.org
>> [mailto:public-grddl-comments-request@w3.org] On Behalf Of
>> Booth, David (HP Software - Boston)
>> Sent: Friday, May 25, 2007 11:50 AM
>> To: public-grddl-comments@w3.org
>> Cc: Jeremy Carroll; McBride, Brian
>> Subject: issue-dbooth-10: Does an XML namespace necessarily
>> imply semantics?
>> This is a personal comment -- not on behalf of HP.
>> This is the formal submission of the comment Jeremy already
>> sent to the
>> WG on my behalf:
>> http://lists.w3.org/Archives/Public/public-grddl-wg/2007May/0061.html
>> Does an XML namespace necessarily imply a certain set of semantics?
>> Suppose Freddy at example.org defines a convenient XML schema for
>> writing a person's legal residence ("a:primaryAddress") a
>> vacation home
>> address ("a:secondaryAddress"), such as:
>> <a:root xmlns:a="http://example.org/AddressSchema.xml">
>>   <a:primaryAddress>25 Park St, Rochester, NY</a:primaryAddress>
>>   <a:secondaryAddress>88 Spring St, Salem, MA</a:secondaryAddress>
>> </a:root>
>> Freddy makes the XML schema definition downloadable from the namespace
>> URI, and separately provides prose documentation to his users
>> explaining
>> the meaning and purpose of a:primaryAddress and a:secondaryAddress in
>> his application.  In essence, Freddy's app treats this document as
>> though it had made the following assertions:
>>   foo:_lucy foo:legalResidence "25 Park St, Rochester, NY".
>>   foo:_lucy foo:vacationAddress "88 Spring St, Salem, MA".
>> Later, Ralph needs a schema for billing and shipping addresses and he
>> notices that Freddy's AddressSchema has the exact form he needs:
>> a:primaryAddress could represent the billing address and
>> a:secondaryAddress could represent the shipping address.  In other
>> words, Ralph wishes to reuse the syntax only.  (This is analogous to
>> implementation inheritance in OO programming.)  Raph notes that an XML
>> schema only defines the structure of a document -- not the
>> semantics --
>> and the namespace spec does not seem to say anything about
>> the semantics
>> of a namespace either.  Ralph reuses Freddy's schema by reference, and
>> provides separate prose documentation to his users explaining that the
>> syntax (only) of Freddy's schema is being reused but the semantics are
>> to be the semantics specified by Ralph.  Example:
>> <a:root xmlns:a="http://example.org/AddressSchema.xml">
>>   <a:primaryAddress>123 Winter St, Palo Alto, CA</a:primaryAddress>
>>   <a:secondaryAddress>444 El Camino, San Diego,
>> CA</a:secondaryAddress>
>> </a:root>
>> In essence, Ralph's app treats this document as though it had made the
>> following assertions:
>>   fum:_desi fum:billingAddress "123 Winter St, Palo Alto, CA".
>>   fum:_desi fum:shippingAddress "444 El Camino, San Diego, CA".
>> Later Freddy decides to update his XML schema document at
>> http://example.org/AddressSchema.xml to declare a GRDDL transformation
>> in the namespace document such that the above example would be GRDDL
>> transformed to RDF.  Ralph may have no knowledge of GRDDL and may be
>> unaware of this change, but suddenly Ralph's documents gain the
>> semantics of Freddy's documents according to the GRDDL spec.
>> Questions
>> Was Ralph wrong to re-use Freddy's namespace and syntax schema while
>> imparting his own semantics to that schema?  If so, what spec forbids
>> this?  (Presumably this is a question for the W3C TAG.)
>> My own view at present is that a namespace should be viewed
>> as implying
>> the semantics that its owner declares, regardless of whether GRDDL is
>> used.  Hence, Ralph should not give his document different semantics
>> than Freddy somehow specifies via his namespace document.  If Freddy's
>> semantics are not clear to Ralph, then Ralph should not use Freddy's
>> namespace, due to the risk of guessing wrong.
>> However, since I do not at present see anything in the
>> namespace spec or
>> the WebArch that forbids this kind of syntax-only reuse, perhaps the
>> GRDDL spec should address the possibility of its allowance.
>> If so, what
>> should the GRDDL spec say?
>> Option 1: Add some warning text in the spec.  This might include
>> suggesting that GRDDL aware agents check last modified times
>> on docs and
>> namespace docs, but this does not seem like it would be reliable.
>> Option 2: Record a postponed issue (possibly to be referred
>> to the TAG).
>> At present I think either option would be okay.
>> David Booth, Ph.D.
>> HP Software
>> +1 617 629 8881 office  |  dbooth@hp.com
>> http://www.hp.com/go/software


 	Harry Halpin
 	Informatics, University of Edinburgh
Received on Friday, 25 May 2007 23:34:47 UTC

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