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Re: Comments on last-call SPARQL draft 20050721, section 2

From: Bijan Parsia <bparsia@isr.umd.edu>
Date: Mon, 12 Sep 2005 09:13:55 -0400
Message-Id: <d1753d849c167cd7dbbea87b975b86ec@isr.umd.edu>
Cc: public-rdf-dawg-comments@w3.org, Graham Klyne <GK@ninebynine.org>, RDF Data Access Working Group <public-rdf-dawg@w3.org>
To: andy.seaborne@hp.com

On Sep 12, 2005, at 7:15 AM, Seaborne, Andy wrote:

> Editorial changes made in response to
> http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2005Sep/ 
> 0002
> Not all the comments are editorial.
> Someone might care to comment on the OWL and literals-as-subjects  
> comment.

See below.

> Graham Klyne wrote:
> ...
>> Section 2.3
>> Concerning the reference to literals-as-subjects.  Is this still an  
>> option for the Semantic Web family?  I understand that OWL (or  
>> OWL-DL) requires that subjects be URIs.  Maybe not a problem, but I  
>> thought I'd mention it.
> Not editorial.
> Comments?

RDF through OWL syntactically forbids literals-as-subjects. However,  
OWL Full allows for equality relations between data values and abstract  
individuals. So, semantically, there is already a sense in which the  
OWL Family allows for literal subjects.

Furthermore, there a smooth path to OWL-DL with subjects as  
literals...first order logic certainly allows for the first place of  
two place predicates to have data values (when it admits such values at  
all) and OWL-DL is a proper subset of FOL. It could be that certain  
extensions to literal subjects would be undecidable, but so's SWRL for  
example. I would expect that a forml of AL-Log would allow for literal  
subjects and robust decidability.

In fact, if you were careful about equalities and class membership, it  
might be a reasonable addition to regular OWL-DL.

Hope this helps.

Bijan Parsia.
Received on Monday, 12 September 2005 13:14:03 UTC

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