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

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Mon, 13 Apr 2009 16:07:34 +0100
Message-Id: <85012189-DE4F-420A-8B9A-238157E35A55@comlab.ox.ac.uk>
Cc: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, public-owl-comments@w3.org
To: Jos de Bruijn <debruijn@inf.unibz.it>
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.
>
>
Received on Monday, 13 April 2009 15:08:12 GMT

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