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

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Tue, 29 May 2007 16:27:44 -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.4.64.0705291627100.28661@tribal.metalab.unc.edu>

On Tue, 29 May 2007, Booth, David (HP Software - Boston) wrote:

> This is not a significant issue from my perspective, since as DanC
> pointed out, the TAG has already answered the question.  (I was not
> aware that it had when I wrote the issue.)
>
> In looking over the GRDDL primer editor's draft:
> http://www.w3.org/2001/sw/grddl-wg/doc29/primer.html
> I don't see any example of using a namespaceTransformation, and that is
> the place where it would have been natural to add an explanation of the
> namespace semantics.  If the primer is expanded to include such an
> example, then I suggest added text along the lines of: "Use of a
> namespace on the root element represents a declaration that the document
> conforms to the semantics of that namespace as defined by the namespace
> owner" and reference the TAG's decision on this.

Thanks David, if we use such an example in the Primer, we will add that 
text.

>
> In short, I'm fine with leaving this to the editors' discretion, so this
> issue can be closed.  I am satisfied with the WG's response.
>
> Thanks
>
> David Booth, Ph.D.
> HP Software
> +1 617 629 8881 office  |  dbooth@hp.com
> http://www.hp.com/go/software
>
>
>> -----Original Message-----
>> From: Harry Halpin [mailto:hhalpin@ibiblio.org]
>> Sent: Friday, May 25, 2007 7:35 PM
>> To: Booth, David (HP Software - Boston)
>> Cc: public-grddl-comments@w3.org; Jeremy Carroll; McBride, Brian
>> Subject: RE: issue-dbooth-10: Does an XML namespace
>> necessarily imply semantics?
>>
>> 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.
>>
>> [1]http://www.w3.org/2004/01/rdxh/spec
>>
>> 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
>>
>>  	Harry Halpin
>>  	Informatics, University of Edinburgh
>>          http://www.ibiblio.org/hhalpin
>>
>

-- 
 				--harry

 	Harry Halpin
 	Informatics, University of Edinburgh
         http://www.ibiblio.org/hhalpin
Received on Tuesday, 29 May 2007 20:27:49 GMT

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