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RE: private review of Profiles, Section 4.3 (OWL 2 RL/RDF rules)

From: Michael Schneider <schneid@fzi.de>
Date: Fri, 17 Apr 2009 20:06:09 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A00125FB13@judith.fzi.de>
To: "Boris Motik" <boris.motik@comlab.ox.ac.uk>
Cc: "OWL 2" <public-owl-wg@w3.org>
>-----Original Message-----
>From: public-owl-wg-request@w3.org [mailto:public-owl-wg-request@w3.org]
>On Behalf Of Boris Motik
>Sent: Friday, April 17, 2009 12:29 PM
>To: 'OWL 1.1'
>Subject: RE: private review of Profiles, Section 4.3 (OWL 2 RL/RDF
>rules)
>
>Hello Michael,
>
>Thanks a lot for your detailed review! Please find my responses inline.
>Here is
>the diff to the changes I made in response to your comments:
>
>http://www.w3.org/2007/OWL/wiki/index.php?title=Profiles&diff=22290&oldi
>d=22225
>
>Regards,
>
>	Boris

Hi Boris!

Thanks for the work. I'm happy with your response, and will not ask for any further changes before LC publication.

There are just two small notes below, mainly for the record.

>> * [technical, change request] All the cardinality restrictions in
>Table 6
>> contain literals of the form "n"^^xsd:nonNegativeInteger. In believe
>this asks
>> for trouble, since presumably only a small fraction of all OWL/RDF
>documents
>> will use xsd:nonNegativeInteger for building cardinality restrictions.
>In
>> comparison, the reverse RDF Mapping uses a function "NN_INT(n)" as a
>> placeholder for all kinds of non negative integer definitions. I
>suggest to
>> use this function in RL, too. This would be ok for the relationship to
>the
>> RDF-Based Semantics, which isn't restricted to a single number
>datatype,
>> either, but only talks about the /value space/ of
>xsd:nonNegativeInteger.
>>
>
>I see that this might be misunderstood; however, I don't believe that we
>have a
>problem formally speaking. We say that the rules are a bunch of
>universally
>quantified clauses, right? Now it all depends on how you interpret the
>literals
>in there. I believe these should be interpreted *semantically*. That is,
>"0"^^xsd:nonNegativeInteger should be interpreted as the integer zero,
>just like
>"0"^^xsd:integer. Thus, if your data contains the latter but the rule
>contains
>the former, the rule still applies because the two values are
>semantically
>equivalent.
>
>I haven't changed anything to this end.

I'm fine with this. However, I think that we should have a word on this 
in the document, or I believe it will become a FAQ, in particular for 
implementers. (I wonder how Ivan treats cardinality restrictions in his
implementation at the moment :-)) But this can be deferred for the 
moment, since it is purely editorial.

>> * [technical, missing(?) rules] Where are the exact-cardinality
>variants of
>> all the max-cardinality restrictions (including max-QCRs)? This looks
>like a
>> significant omission to me that may lead to problems in practice.
>>
>
>The rule set contains exactly those rules that correspond to the grammar
>of OWL
>2 RL (the DL view of the profile). The grammar does not allow for exact
>cardinality restrictions, and so there are no rules for these either.
>
>Note also that you can't really have exact cardinality other than 0, as
>this
>would involve existential quantification (which we don't want to have in
>OWL 2
>RL). Thus, it is not clear to me that allowing exact cardinality 0 (in
>both the
>DL and the RDF view of the profile) would be all that useful.

Ah, I see, I missed the point that ExactCardinality is not in the fragment.

Just a point of clarification: I was only proposing to exactly 
mirror the set of "max" rules. So in the case of exact-1, this 
would have meant that there would have only been rules of the 
kind "if there are two triples s p o1 and s p o2, then o1 = o2". 
I did not ask for rules that introduces bNodes. But this 
discussion is moot now, given your argument above.

Cheers and thanks,
Michael

--
Dipl.-Inform. Michael Schneider
Research Scientist, Dept. Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: michael.schneider@fzi.de
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Received on Friday, 17 April 2009 18:06:51 GMT

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