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"FAST" OWL and "Greater" OWL

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Tue, 24 Sep 2002 18:51:06 +0100
Message-ID: <15760.42506.802025.536387@merlin.horrocks.net>
To: pat hayes <phayes@ai.uwf.edu>, www-webont-wg@w3.org

Several points regarding your latest document(s).

1. I have been arguing for a long time that trying to resolve the
layering problem (or any issue come to that) by inventing a new logic
is not a sensible thing for a standardisation working group to do. And
make no mistake, "Greater OWL" is a new logic about which, by Pat's
own admission, we currently know very little. Peter has been doing a
great job of pointing out just some of the immediately obvious
pitfalls. Pat is apparently willing to wager a glass of scrumpy that
he can fix (some of) the problems. Are we willing to bet the future of
OWL against a glass of scrumpy?

To borrow Jim Hendler's drug analogy, the drug we are being offered
here has been knocked together in a few months, we know little about
its possible effects (except by analogy with similar drugs), and it
has never been subjected to clinical trials. I think that these facts
would make a material difference to most people's decision as to
whether or not they wanted to risk taking the drug.

2. It is disingenuous, or at least misguided, to denote the more
restricted form of layering as "Fast OWL", to depict the restrictions
as strange and unnecessary, and to imply that their only justification
is to facilitate the use of some weird kind of reasoning system.

In fact, "Fast OWL" could better be described as "First Order OWL":
the restrictions are just those required to keep OWL within the
standard first order framework, i.e., where classes directly
correspond to formulae with one free variable, subsumption is
implication, etc. Unlike "Greater OWL", the languages within this
framework, up to and including standard FOL, have been extensively
studied and are very well understood.

Staying within this framework imbues OWL with a simple and very well
understood semantics, and allows applications to use wide range of
reasoning engines ranging from DLs through to full FOL
systems. Moreover, it would facilitate the future extension of the
language, i.e., to include the expressive power of full FOL.

3. If we really need a document describing how OWL can be embedded in
RDF with semantic constraints such that OWL entailment and RDF
entailment coincide, then I would like to draw the WGs attention back
to Peter's proposal of Aug 28 last [1] that details a much simpler way
to do this than "Greater OWL".

Regards, Ian

[1] http://lists.w3.org/Archives/Public/www-webont-wg/2002Sep/att-0136/01-part
Received on Tuesday, 24 September 2002 12:54:05 GMT

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