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Re: wording on Unknown returns in Conformance

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 24 Sep 2008 12:44:16 -0400 (EDT)
Message-Id: <20080924.124416.104221009.pfps@research.bell-labs.com>
To: alanruttenberg@gmail.com
Cc: public-owl-wg@w3.org

This is not so bad, but it still suffers from the problem that a trivial
program can be minimally conforming.

peter


From: "Alan Ruttenberg" <alanruttenberg@gmail.com>
Subject: Re: wording on Unknown returns in Conformance
Date: Wed, 24 Sep 2008 12:37:49 -0400

> I was thinking about something along the lines of (specific words could
> change). My changes in italics. There's probably a better word than
> "minimally
> conforming" but I can't think of one right now.
> 
> An minimally conforming OWL 2 Full entailment checker is an OWL 2
> entailment
> checker that takes RDF documents as input, and uses the RDF-Based
> Semantics
> [OWL 2 RDF-Based Semantics]. It must return True only when O1 entails
> O2,
> and it must return False only when O1 does not entail O2. It may return
> Unknown if it is not capable of determining whether an entailment holds
> or
> not.
> A complete OWL 2 Full entailment checker is a minimally conforming OWL 2
> Full entailment checker that should not return unknown.
> 
> Then, in section 2.2.1
> 
> It *must* provide a means to determine the semantics it uses (either the
> Model-Theoretic Semantics [OWL 2
> Semantics<http://www.w3.org/2007/OWL/wiki/Test#ref-owl-2-semantics>]
> or the RDF-Based Semantics [OWL 2 RDF-Based
> Semantics<http://www.w3.org/2007/OWL/wiki/Test#ref-owl-2-rdf-semantics>]),
> and whether it is minimally conformant or complete; for example, in its
> supporting documentation.
> 
> Similarly for other profiles.
> 
> I would add a note that at the time of publication it isn't known
> whether
> complete conformance for OWL Full is possible.
> 
> -Alan
> 
> On Wed, Sep 24, 2008 at 12:26 PM, Peter F. Patel-Schneider <
> pfps@research.bell-labs.com> wrote:
> > Huh?  What is this, and how would it be done.
> >
> > peter
> >
> > From: "Alan Ruttenberg" <alanruttenberg@gmail.com>
> > Subject: Re: wording on Unknown returns in Conformance
> > Date: Wed, 24 Sep 2008 12:17:07 -0400
> >
> >> I had thought that it might be worth distinguishing distinct levels
> of
> >> conformance - complete versus incomplete. Do you think that would be
> a
> >> good idea? It bothers me a bit that conformance as specified for OWL
> >> Full, as stated now, is not known to be possible.
> >> -Alan
> >>
> >>
> >> On Wed, Sep 24, 2008 at 10:04 AM, Peter F. Patel-Schneider
> >> <pfps@research.bell-labs.com> wrote:
> >> >
> >> > There have been some comments on the "should not" wording in the
> >> > conformance part of the Test and Conformance document.
> >> >
> >> > The current wording includes
> >> >
> >> > An OWL 2 Full entailment checker is an OWL 2 entailment checker
> that
> >> > takes RDF documents as input, and uses the RDF-Based Semantics [OWL
> 2
> >> > RDF-Based Semantics]. It MUST return True only when O1 entails O2,
> and
> >> > it MUST return False only when O1 does not entail O2. It SHOULD NOT
> >> >  return Unknown.
> >> >
> >> > Without the last sentence, a trivial checker, i.e., one that always
> >> > returned "Unknown" would be just as good an OWL 2 Full entailment
> >> > checker as one that tried hard.
> >> >
> >> > Even worse, if the last sentence was removed from
> >> >
> >> > An OWL 2 DL entailment checker is an OWL 2 entailment checker that
> >> >  takes OWL 2 DL ontology documents as input, and uses the Model
> >> > Theoretic Semantics [OWL 2 Semantics]. It MUST return True only
> when
> >> > O1 entails O2, and it MUST return False only when O1 does not
> entail
> >> >  O2. It SHOULD NOT return Unknown.
> >> >
> >> > then a trivial checker would be just as good as a complete reasoner
> for
> >> > OWL 2 DL.
> >> >
> >> >
> >> > I thus feel that there needs to be some wording in the conformance
> >> > document to show that trivial checkers, or unnecessarily incomplete
> >> > checkers, are not as good as ones that return "Unknown" in fewer
> cases.
> >> >
> >> > Remember that "should not" is not the same as "must not".  A
> checker
> >> > could return "Unknown" if
> >> > 1/ it ran out of resources (memory, time, etc.); or
> >> > 2/ it is an incomplete reasoner (for OWL 2 Full, for example, or
> even
> >> >   for OWL 2 DL).
> >> > The above reasons (or others) could be used by entailment checkers
> to
> >> > provide a justification for "Unknown" answers.  I feel, however,
> that
> >> > this is outside the scope of the specification.
> >> >
> >> > Perhaps it would be useful to add some wording on justifying
> "Unknown"
> >> > to the document, but I think that most of this is implied by the
> use of
> >> > "should not".
> >> >
> >> > peter
> >> >
> >> >
> >
Received on Wednesday, 24 September 2008 16:45:01 UTC

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