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Re: [LC Response] To Jos de Bruijn Re: a few comments about the OWL 2 drafts

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Mon, 13 Apr 2009 17:13:40 +0200
Message-ID: <49E356A4.7020006@inf.unibz.it>
To: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
CC: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, public-owl-comments@w3.org
Dear Ian,

Thank you for the e-mail.  I am satisfied with the working group's response.

Best, Jos

Ian Horrocks wrote:
> Dear Jos,
> 
> In response to your comment the WG has now added negative class and
> property assertions to the OWL 2 RL profile (see [1]).
> 
> 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.
> 
> [1] http://www.w3.org/2007/OWL/wiki/Profiles#OWL_2_RL
> 
> Regards,
> Ian Horrocks
> on behalf of the W3C OWL Working Group
> 
> 
> On 26 Mar 2009, at 16:06, Jos de Bruijn wrote:
> 
>> Dear Peter,
>>
>> Thank you for the response. I am satisfied with most of the
>> answers/edits. There are a few things I do want to come back to, though:
>>
>>> Direct Semantics document:
>>>
>>> The definition for datatype maps in Direct Semantics extends datatype
>>> maps from RDF Semantics, in particular for facets.
>>
>> Not really.  The treatment of datatypes boils down to the same thing,
>> but the style of definition is quite different.  In RDF, datatype maps
>> are partial mappings from the set of IRIs to the set of datatypes. In
>> OWL 2 they are defined in quite a different way. I was just wondering
>> why you chose a new way of defining them.
>>
>> This is not a big issue, though.
>>
>>> Profiles document:
>>>
>>> As stated in the document, OWL 2 RL is designed for easy and efficient
>>> implementation using existing forward-chaining rule systems.  Adding
>>> owl:Thing or reflexive object properties needs rules that operate over
>>> all individuals, which goes against efficiency, and may not even be
>>> possible in some rule systems.
>>
>> One can avoid universal quantification by using grounding, so all rule
>> reasoners that can deal with the current OWL 2 RL are able to deal with
>> these extensions.
>>
>> But I accept your argument about efficiency.
>>
>>
>>> Similarly, most rule systems are
>>> designed for positive ground facts which dictates against allowing
>>> negative property assertions.
>>
>> This argument puzzles me, because there are many constructs in OWL 2 RL
>> that allow expressing negative information, e.g.,
>> IrreflexiveObjectProperty, AsymmetricObjectProperty, not to mention the
>> negative type information of literals. Plus, negated facts are easily
>> encoded as class axioms using ObjectOneOf, ObjectHasValue, and
>> owl:Nothing. So, leaving out these features to improve the efficiency of
>> OWL 2 RL reasoning.
>>
>> In summary, I still don't understand why negative class and property
>> assertions are not allowed in the profile.
>>
>>
> 

-- 
+43 1 58801 18470        debruijn@inf.unibz.it

Jos de Bruijn,        http://www.debruijn.net/
----------------------------------------------
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enough.
  - Thomas Fuller
Received on Monday, 13 April 2009 15:14:28 GMT

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