W3C home > Mailing lists > Public > public-powderwg@w3.org > December 2008

Re: Request for two new media types submitted

From: Stasinos Konstantopoulos <konstant@iit.demokritos.gr>
Date: Thu, 18 Dec 2008 08:06:38 +0200
Cc: Phil Archer <phil@philarcher.org>, Bjoern Hoehrmann <derhoermi@gmx.net>, Public POWDER <public-powderwg@w3.org>, Ivan Herman <ivan@w3.org>, Ralph Swick <swick@w3.org>
Message-Id: <B182E53F-DF8C-45DE-8ED9-593B481AD3C2@iit.demokritos.gr>
To: Eric Prud'hommeaux <eric@w3.org>


On Dec 16, 2008, at 8:13 PM, Eric Prud'hommeaux wrote:

> * Stasinos Konstantopoulos <konstant@iit.demokritos.gr> [2008-12-10  
> 23:32+0200]
>>
>> Eric, hi.
>>
>>
>> On Dec 8, 2008, at 5:30 PM, Eric Prud'hommeaux wrote:
>>
>>> Minor nit:
>>> [[
>>> We extend RDF with the datatype properties ...
>>> ]]  http://www.w3.org/TR/2008/WD-powder-formal-20081114/#SE
>>>
>>> would imply to me that the RDF machinery must be extended, as  
>>> opposed
>>> to the application interpreting the RDF graph. Maybe something like:
>>> "POWDER-S uses an <a
>>> href="http://www.w3.org/TR/2004/REC-owl-semantics-20040210/syntax.html#owl_DatatypeProperty_syntax
>>> ">OWL DatatypeProperty</a> to relate a resource to a regular
>>> expression which that resource matches. While POWDER-S uses OWL
>>> classes to group resources, any engine determining if a resource
>>> belonged in one of these OWL classes would need to be able to test a
>>> resource against a regular expression."
>>
>> No, not at all, it is the underlying RDF representation where the
>> explicit data lives that is being extended; the inference layer is
>> not affected. Of course inference engines that directly manipulate
>> RDF data need to implement the extension, but in situations where a
>> clean interface exists between the two, the inference engine does
>> not need to know why the wdrs:matchesregex triples are asserted.
>
> An unextended RDF parser, database, and SPARQL query engine can parse,
> store and return assertions like:
>  _:redRestriction wdrs:matchesregex "^http://foo.example/redStuff.*" .
>  <http://foo.example/redStuff/redShoe> wdrs:matchesregex "^http://foo.example/redStuff.* 
> " .

Exactly.

> Telling people that they require an extended RDF is misleading.

Telling people otherwise would be misleading. The extension is  
necessary in order to
have the wdrs:matchesregex triples that the query engine or OWL  
reasoner will retrieve
and act upon. Note how in Section 4.3 of the Formal doc a pair <u,re>  
is in the
extension of wdrs:matchesregex IFF the string representation of the  
IRI identifier of
resource <u> matches regular expression <re>; there is no requirement  
that anything
has been explicitly asserted for wdrs:matchesregex to have <u,re> in  
its extension.

Of course one is welcome to manually assert wdrs:matchesregex triples,  
as long as
this is done consistently with the requirements of the definition in  
Section 4.3. In this
case one has become a wetware implementation of the extension.

> I also noticed
>        <owl:intersectionOf rdf:parseType="Collection">
>          <owl:Restriction>
>             ...
>          </owl:Restriction>
>        </owl:intersectionOf>
>
> which is an intersection of one class. How about this instead?
>
>      <owl:Restriction>
>         ...
>      </owl:Restriction>

The two are semantically equivalent, and the Formal doc explicitly  
allows your implementation
to use either or any other syntactic variation.

The normative document (and our reference implementation) prefers the  
former, as it
preserves a syntactic symmetry with cases where multiple classes are  
intersected. This symmetry
makes the transform cleaner (avoiding unnecessary if-then branches in  
the document) and thus easier
to implement and check.

s
Received on Thursday, 18 December 2008 06:07:22 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:42:14 GMT