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

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]).

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you are satisfied with the working group's response to your comment.


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 UTC