Draft second response for LC Comment 51a RM1-2

[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.

Received on Thursday, 12 March 2009 18:10:50 UTC