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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 12:26:36 -0400 (EDT)
Message-Id: <20080924.122636.223842725.pfps@research.bell-labs.com>
To: alanruttenberg@gmail.com
Cc: public-owl-wg@w3.org

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 16:27:26 UTC

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