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layering (was Re: Patel-Schneider Paradox ...)

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 18 Jan 2002 11:58:20 -0500
To: Frank.van.Harmelen@cs.vu.nl
Cc: www-webont-wg@w3.org
Message-Id: <20020118115820B.pfps@research.bell-labs.com>
From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Subject: Re: Patel-Schneider Paradox ...
Date: Sat, 19 Jan 2002 17:22:40 +0100

> "Peter F. Patel-Schneider" wrote:
> 
> > Well, in some sense, no change is necessary.  RDFS does not appear to have
> > any problems in and of itself.  True extensions to RDFS can be made and also
> > do not appear to have any problems.  The problems only occur when a
> > same-syntax extension is mandated.
>   ^^^^^^^^^^^^^^^^^^^^^
> 
> Indeed.
> 
> From my understanding of the discussions at Bell Labs, 
> the problem does indeed only occur when OWL must be a "same-syntax
> extension", ie when OWL would be required to  
> - use RDF syntax, >*and*<
> - be a semantic >*extension*< of RDF
> 
> One of the proposals on the table was to keep the first and drop the second.
> OWL would then include most of the inferences sanctioned by RDF, but not
> all of them, making it not a strict extension.  
> (In particular OWL would loose some RDF-inferences that wouldn't make
> much sense from an OWL point of view anyway).  
> 
> This is the option that I would currently favour.
> 
> Frank.
>    ----
> (Peter, please correct me if my understanding is wrong).

Nothing wrong with your understanding here.

However, such a relationship is dishonest, at least when it is described as
an extension of RDF(S) that uses RDF syntax but violates the RDF(S) meaning
for that syntax.  Further, in various discussions over the last week, see
www-archive@w3.org for an archive of (most of) them, I've come to believe
that such dishonesty is a very, very bad idea.

Making the relationship honest is trivial, at least technically.  It
suffices to describe the syntax of OWL as N-triples instead of describing
OWL as layered on top of RDF(S) but not using (all of) the semantics of
RDF(S).  The non-technical issues are much harder to solve; I think that it
would be necessary to have many very-noticable disclaimers that OWL is not
an extension of RDF, or layered on top of RDF, or ....  The political
issues may in fact be even harder to solve here---it may just not be
possible to not say that OWL is layered on top of RDF.

peter
Received on Friday, 18 January 2002 11:59:11 GMT

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