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Re: WEBONT "HOMEWORK" (FOL or class/property)

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Thu, 6 Dec 2001 19:41:05 -0500
Message-ID: <15376.4129.448112.919052@localhost.localdomain>
To: Dan Connolly <connolly@w3.org>
Cc: Pat Hayes <phayes@ai.uwf.edu>, "Smith, Ned" <ned.smith@intel.com>, www-webont-wg@w3.org
On December 6, Dan Connolly writes:
> Pat Hayes wrote:
> [...]
> > I think
> > that as a basic ontology language, DAML+OIL is 'warped' by its being
> > a class/property language rather than a conventional logical
> > language. For things that are simple and natural to state as in
> > class/property terms it is fine, but other kinds of propositions
> > require one to introduce very artificial classes defined in terms of
> > restrictions in order to state simple facts (and simple queries), and
> > the resulting complexities of needing to learn to think in this odd
> > way add further barriers to the already considerable difficulties of
> > using DAML+OIL.
> That's my experience as well.
> For example, I have some tools for doing sort of visual stylesheets
> for RDF (http://www.w3.org/2001/02pd/) ... stylesheets say things like
> 	draw working groups using blue circles.
> Given my background, it's quite straightforward to phrase that as:
> 	(forall (?x)
> 		(=> (WorkingGroup ?x) (and (color ?x 'blue) (shape ?x 'circle))))
> and I can twist my head a little to write it in N3:
> 	this log:forAll :x.
> 	{ :x a :WorkingGroup } log:implies { :x g:color "blue"; g:shape
> "circle"}.
> but writing it in DAML+OIL hurts pretty badly:
> 	:WorkingGroup rdfs:subClassOf [
> 		ont:onProperty g:color; ont:hasValue "blue"],
> 		[ ont:onProperty g:shape; ont:hasValue "circle"].
> now maybe N3 isn't a very good syntax for DAML+OIL, but
> translated back to natural language, we'd get:
> 	WorkingGroup is a subclass of the class of things
> 		that have color blue
> 		and a sublcass of the class of things that
> 		have shape circle.
> which is not how I think. I'm trying to train myself, but
> it looks daunting...
> > I would suggest something like 
> > a 'neat' syntax for FOL - perhaps a subset, eg a constructive or 
> > intuitionist subset(?) - with a distinguished typing syntax that is 
> > similar in power (though maybe not quite in form) to DAML+OIL, ie a 
> > genuine logical extension of DAML+OIL.
> I like the idea of constructive/untuitionist subset of FOL appeals
> to me, based on my experience and research.
> I have also worked a lot with larch, which is a sorted first-order
> logic, and the sorts did make the syntax nice.
> But this is stretching our charter somewhat. This is the
> sort of design I work on in the context of Advanced Development,
> not working group stuff, usually. I wouldn't mind if we wanted to
> stretch our charter that way, but only if pretty much everybody
> else prefers this sort of design too.

I understand Pat and Dan's point. However, both from the point of view
of our extremely tight schedule, and from my understanding of the
charter, I think we should concentrate on refining rather than
(fundamentally) redesigning.

Bearing this in mind, I think it would be very useful if, at least as
one aspect of their work, the use case groups took DAML+OIL as a
reference point and told us the good and bad points of the language
w.r.t. their use case. It would also help if any "wish lists" were
categorised along the lines of "essential", "useful", "would be nice",

Regards, Ian

> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 6 December 2001 16:28:34 UTC

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