Re: Draft second response for LC Comment 51a RM1-2

I am not sure it is wise to refer to a formal objection (although this
is procedurally correct). Let us not ask for extra formal trouble:-) I
would also not open the door on possible changes after CR in this
respect; afaik, this feature was implemented in OWL 1 already, this is
not a feature that OWL 2 introduced as new (unless I miss something
fundamental here).

He also refers to the argument on backward compatibility with OWL 1 as
putting our head in the sand which is not as simple as he says per the
charter of this group.

Ie, I shortened the answer that way:

[[[
The Working Group acknowledges that multi-valued data properties
together with datatype facets do pose an implementation burden. However,
the group is not chartered[1] to do any changes that would break the
backward compatibility with OWL 1, which had numerous implementations
with non-functional datatypes, as well as deployment of ontologies
possibly relying on that feature. Note also that no erratum was reported
on this feature on OWL 1[2]. Therefore, the Working Group does not
intend to change OWL 2 in this way.

Regards,
Peter F. Patel-Schneider
on behalf of the W3C OWL Working Group

[1] http://www.w3.org/2007/06/OWLCharter.html
[2] http://www.w3.org/2001/sw/WebOnt/errata

]]]

How does that sound?

Ivan

Peter F. Patel-Schneider wrote:
> [Draft second response for LC Comment 51a RM1-2]
> 
> To: Ralf Moeller <r.f.moeller@tu-harburg.de>
> Subject: [LC Response] To Ralf Moeller Re: OWL2
> 
> Dear Ralf:
> 
> This message is in reply to your comment available as
> <http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0059.html>,
> on the OWL 2 Web Ontology Language last call drafts; the initial
> response from the working group
> <http://lists.w3.org/Archives/Public/public-owl-comments/2009Feb/0031.html>;
> and your subsequent reply, available as
> <http://lists.w3.org/Archives/Public/public-owl-comments/2009Mar/0018.html>
> 
> 
> The Working Group acknowledges that multi-valued data properties
> together with datatype facets do pose an implementation burden.
> However, the Working Group feels that multi-valued data properties are
> the correct way to go in OWL 2.
> 
> Therefore, the Working Group does not intend to change OWL 2 in this
> way, at least for now.  If implementation experience shows that this
> part of OWL 2 is too difficult to implement the Working Group will, of
> necessity, revisit this decision.
> 
> 
> You may, if you wish, press this matter further by filing a formal
> objection to this aspect of OWL 2, using standard W3C procedures.
> 
> Regards,
> Peter F. Patel-Schneider
> on behalf of the W3C OWL Working Group
> 
> 
> == Past Messages ==
> 
> 
> From: Ralf Moeller [mailto:r.f.moeller@tu-harburg.de]
> Sent: Friday, March 06, 2009 1:45 PM
> To: Michael Schneider
> Subject: Re: [LC Response] To Ralf Moeller Re: OWL2
> 
> Dear Michael,
> 
> I would like to let you know that I cannot really be satisfied with the
> response.  I have pointed out loose ends in OWL 2 that go back to even
> looser ends in OWL 1.  We should not bury our head in the sand and
> argue: We cannot change sth because this would break backward
> compatibility with OWL 1.
> 
> Now it is the time to get up the nerve to do sth that appears to be a
> serious flaw :-)
> 
> Best regards,
> 
> Ralf
> 
> 
> 
> From: Michael Schneider
> 
> Dear Ralf,
> 
> Thank you for your comments
> <http://lists.w3.org/Archives/Public/public-owl- comments/2009Jan/0059.html>
> on the OWL 2 Web Ontology Language last call drafts.
> 
> Your mail actually contains three distinct comments. This response
> exclusively covers your first comment. There will be additional
> responses to your other two comments.
> 
> In your first comment, you state:
>   I strongly recommend to change the OWL2 specification in such a way
>   that data properties are always functional.
> 
> The working group acknowledges that by applying the approach
> you mention in your comment it would indeed be sufficient
> if all data properties would be functional.
> 
> However, the working group is aware of the fact that the
> original OWL language did not restrict data properties to
> be functional. Therefore, restricting data properties to be
> functional in OWL 2 would break backwards compatibility with OWL.
> 
> For this reason, the working group has decided not to make
> the requested change to OWL 2.
> 
> 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,
> Michael Schneider
> on behalf of the W3C OWL Working Group
> 
> 
> 
> http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0059.html
> From: Ralf Moeller [mailto:r.f.moeller@tu-harburg.de]
> 
> 1. I think it is a severe problem not to restrict data properties to
> functional properties by definition.  Many problems with implicit
> cardinality restrictions occur if the range of data properties is
> restricted (e.g. via range specs such as xsd:int or xsd:integer with
> arbitrary conjunctions of datarange specifications inclusing facets with
> minInclusive and maxInclusive). Implicit cardinality restrictions
> emerge, and this makes the implementation very difficult, and IMHO the
> semantics is hard to understand.  Further, some facets such as
> owl:length imply number restrictions for strings.  I have no idea, how
> to deal with the owl:pattern facet (decidability problems?).
> 
> Arbitrary data properties are not needed: If, for instance, one might
> want to use multi-value data properties for multiple names of a Person,
> say, one can always introduce domain objects of class PersonName with a
> single-value data property namestring.  PersonNames can be set into
> relation to Person as usual via a role hasName, say. It is easy to
> restriction the number of names, etc. With this kind of represenation we
> can associate additional information with person names such as, for
> instance, whether a name is a nickname or not.
> 
> If we say (at-least 2 hasName) then it is not guaranteed that the (two
> or more) PersonName instances have different namestrings. If hasName was
> a data property, this would be implied, leading to very tricky
> constraints, which would make a sound and complete implementation very
> difficult in the context of Aboxes and additional at-most restrictions
> for the hasName data property.
> 
> I strongly recommend to change the OWL2 specification in such a way that
> data properties are always functional.
> 
> 
> 
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
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