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draft response for LC comment 31

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 13 Feb 2009 23:52:02 -0500 (EST)
Message-Id: <20090213.235202.262250180.pfps@research.bell-labs.com>
To: public-owl-wg@w3.org

[Response for LC Comment 31]

Dear Frank (and many others),

Thank you for your message
on the OWL 2 Web Ontology Language last call drafts, which the WG has
taken to concern adding a syntactic marker for the expressive power of
used in an ontology, including which profile the ontology belongs

One problem with having an expressive power marker in the header of an
OWL ontology is that there are syntaxes for OWL ontologies, in
particular the preferred syntax, RDF/XML, where the header information
is mixed in with the rest of the ontology.  Recovering the ontology
header in such syntaxes can thus require parsing the entire ontology.
Note that simple text processing is not adequate as the marker syntax
could occur in places where should not be interpreted as the marker,
e.g., in comments or not attached to the ontology node.

Another problem is how to treat cases where the expressive power of the
ontology does not match the marker.  This is very different from what to
do if an ontology does adequately reflect reality.  Should tools be
required to reject ontologies where the expressive power of the ontology
is greater than what the marker states?  Should tools be required to
reject ontologies where the expressive power of the ontology is less
than what the marker states?  Should nothing be said?  What guarantees
should a search for expressive markers provide?  The answers to these
questions are not obvious.

The current situation leaves open the possibility that users will get
together and, through practice, provide the answers to these thorny
questions.  Ontology annotations can be used to support this effort.  If
a body of practice arises, then it may be appropriate for a subsequent
working group to consider adding this practice to OWL.

Therefore the OWL WG does not intend to make any changes in response to
your comment.

The discussion of WG issue 111 (see
http://www.w3.org/2007/OWL/tracker/issues/111) is not directly related
to expressive power markers for OWL ontologies.  Instead it more touches
on the situation where an ontology only uses the expressive power of OWL
2 DL, but is supposed to be interpreted as an OWL 2 Full document, i.e.,
that it could not have a finite interpretation.  The WG noticed that in
such cases it is always possible to add an
OWL-2-Full-semantically-vacuous triple to the ontology that is not
acceptable in OWL 2 DL, and decided that this would be the preferred way
to disambiguate.  Some of the discussion of issue 111 did touch on
markers for expressive power but the issue itself did not require a
solution to this problem.

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. 

Peter F. Patel-Schneider
on behalf of the W3C OWL Working Group 
Received on Saturday, 14 February 2009 05:20:32 UTC

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