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Re: re-post: comments on OWL 2 RL Profile (April 21 2009 public draft)

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Mon, 18 May 2009 16:07:31 +0100
Message-Id: <C0AD7D8B-124F-4850-9CDC-1540907E4134@comlab.ox.ac.uk>
Cc: public-owl-comments@w3.org
To: BenjaminG@vulcan.com
Dear Benjamin,

Thank you for your comment
      <http://lists.w3.org/Archives/Public/public-owl-comments/ 
2009May/0024.html>
on the OWL 2 Web Ontology Language last call drafts.

Regarding the semantics of rule systems, a detailed discussion of  
these matters would be far beyond the scope of this document (which  
is, in the end, primarily specification). We would expect a reader  
interested in the design to consult the references provided. A few  
words and an additional reference have, however, been added [1].

Regarding establishing a mechanism for recognizing and naming useful  
subsets of expressiveness, it is outside the remit of the working  
group as we cannot set up a *process* of indefinite length at the  
W3C. We will pass the suggestion on to Semantic Web Coordination  
Group. Alternatively, the OWLED workshop series is a good place for  
this kind of work [2], and suitable subsets could be the subject of  
future W3C member submissions in this area.

Regarding a primer on implementation design considerations and  
techniques, it is both far beyond the scope of this Working Group and  
not possible given our current resource constraints. Furthermore,  
such a document should be kept up to date, which is difficult to do  
with a W3C technical report. This seems to be an ideal document for  
various third parties to produce.

Regarding theorem PR1, producing a worked out proof would be a  
tedious and, we believe, not especially enlightening task. The proof  
sketch should be sufficient to be convincing and to allow the  
interested reader to fill in any missing details.

Regarding the expressive restrictions in OWL 2 RL, some features have  
been omitted in order to facilitate "easy and efficient  
implementation using existing forward-chaining rule systems".  
Reflexive object properties, for example, would require rules that  
operate over all individuals, which is likely to compromise  
efficiency, and may not even be possible in some rule systems. It may  
be that some of these features could, in theory, be added, but we  
have been mindful of specific major systems (such as Oracle and Jena)  
and their implementation concerns.

[1] http://www.w3.org/2007/OWL/wiki/index.php? 
title=Profiles&diff=23681&oldid=23680
[2] http://www.webont.org/owled/

Please acknowledge receipt of this email to <mailto:public-owl- 
comments@w3.org> (replying to this email should suffice). In your  
acknowledgment please let us know whether or not you are satisfied  
with the working group's response to your comment.

Regards,
Ian Horrocks
on behalf of the W3C OWL Working Group
Received on Monday, 18 May 2009 15:08:08 GMT

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