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[LC Response] To Chimezie Ogbuji Re: Comments for OWL2-RL profile

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 04 Mar 2009 17:28:22 -0500 (EST)
Message-Id: <20090304.172822.140857481.pfps@research.bell-labs.com>
To: ogbujic@ccf.org
Cc: public-owl-comments@w3.org
Dear Chimezie,

Thank you for your message
<http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0039.html>
on the OWL 2 Web Ontology Language last call drafts.  

Arbitrary RDF graphs can include constructs that have surprising
consequences.  The reasons for these are many and varied, including
effects on the "syntax" of OWL 2.  Because there are so many ways in
which the rules could incorrect, the working group has decided not to
exactly characterize how the incorrectness arises, but instead has
included a mention that arbitrary RDF graphs can affect the
underpinnings of OWL, as follows:

  For ontologies satisfying the syntactic constraints described in
  Section 4.2, a suitable rule-based implementation will have desirable
  computational properties; for example, it can return all and only the
  correct answers to certain kinds of query (see Section 4.3 and
  [Conformance]). Such an implementation can also be used with arbitrary
  RDF graphs. In this case, however, these properties no longer hold —
  in particular, it is no longer possible to guarantee that all correct
  answers can be returned*, for example if the RDF graph uses the
  built-in vocabulary in unusual ways.*

There are an infinite number of RDFS axiomatic triples, so including
them all in the OWL 2 RL rules does not directly lead to an effective
rule implementation.  There are some RDFS rules that produce
consequences that are not relevant to the conclusions guaranteed by
Theorem PR1.  Listing all the "deficiencies" is not particularly easy,
and would probably only confuse the issue.  The working group has
therefore decided not to be more explicit in the preamble to Theorem
PR1.

The diffs can be found at
<http://www.w3.org/2007/OWL/wiki/index.php?title=Profiles&diff=18739&oldid=18708>

Please acknowledge receipt of this email to
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Regards,
Peter F. Patel-Schneider
on behalf of the W3C OWL Working Group 

No trees are known to have been harmed in the preparation of this
response.
Received on Wednesday, 4 March 2009 22:28:11 GMT

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