Re: draft response for LC comment 32 CO1

From: Ivan Herman <ivan@w3.org>
Subject: Re: draft response for LC comment 32 CO1
Date: Fri, 20 Feb 2009 09:33:06 +0100

> Well... although what you say is technically true, I would not find it
> unreasonable if some characteristic _examples_ would be added to the
> profile document for both cases that Chime refers to. This tough
> rebuttal is a little bit to brisk for my taste, and we should have some
> more explanation in our documents in my view. (Whether this is in the
> profile or somewhere else like the primer is of course a different issue!)
> 
> I just came up with some things that we could add:
> 
> - For his first comment, we could, eg, refer to the fact that arbitrary
> RDF graphs may include statements on the otherwise reserved vocabulary
> with all kinds of funny consequences, or that they would allow defining
> functional datatype properties whose consequences are a bit unpredictable.

Fine.  I'll put in something like:

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.*

> - An example of the (missing) consequences due to the missing RDF(S)
> axiomatic triples and some of the entailement rules is that
> 
> rdf:_i rdf:type rdfs:ContainerMembershipProperty . (axiomatic rule)
> meaning that
> rdf:_i rdfs:subPropertyOf rdfs:member . (rdfs12 entailement rule)
> 
> If these were around, an OWL RL user could handle container membership
> more easily with those rules.

I don't know whether *these* triples and rules provide an example of the
missing inferences.  Perhaps Boris can comment or provide an example.

> Ivan

peter


> Peter F. Patel-Schneider wrote:
>> [Draft Response for LC Comment 32:] CO1
>> 
>> 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 be
>> more explicit in the introduction to OWL 2 RL.
>> 
>> 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.
>> 
>> 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,
>> 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.
>> 
> 
> -- 
> 
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/

> mobile: +31-641044153
> PGP Key: http://www.ivan-herman.net/pgpkey.html

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Received on Friday, 20 February 2009 10:01:15 UTC