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Re: SEMANTICS - we need them NOW

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 05 Aug 2002 23:06:59 -0400
To: connolly@w3.org
Cc: horrocks@cs.man.ac.uk, www-webont-wg@w3.org
Message-Id: <20020805230659O.pfps@research.bell-labs.com>

From: Dan Connolly <connolly@w3.org>
Subject: Re: SEMANTICS - we need them NOW
Date: 05 Aug 2002 13:20:43 -0500

> On Mon, 2002-08-05 at 10:32, Ian Horrocks wrote:
> > 
> > Dear All,
> > 
> > As you may have noticed from the discussion about testing, we are
> > already in trouble within the WG because we have so far failed to
> > resolve the central question of the semantics of the language.
> Huh? Discussion of test cases is one of the ways that we decide
> the central questions of semantics.

Agreed.   But note what you just said.  

> > In
> > particular, it really makes little sense to continue with work on
> > developing a test suite until we know the meaning of the language we
> > are supposed to be testing.
> My experience says developing tests as we make the relevant
> decisions is best.

Again agreed.  But, again, note what you just said.

Test cases without semantics can be very dangerous.  In particular, it is
possible to have a collection of test cases that all appear to be fine, but
that do not lead to a well-defined semantics.  (Think of the test cases that I
put together leading to the paradoxes.)  

Small collections of test cases can be used to distinguish between
different behaviours of a formalism, or even to drive the search for
meaning for a formalism.  However, test cases in the absence of a meaning
for a formalism are not useful.

I feel that decisions on test cases (and other things as well, by the way)
are being made without an overall view (or, at least, with multiple,
diverging, overall views) of what OWL constructs are supposed to mean.  I
fear that we are in danger of ending up with a collection of test cases
that cannot be extended to a cohesive whole.  

> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/

Peter F. Patel-Schneider
Bell Labs Research
Received on Monday, 5 August 2002 23:07:42 UTC

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