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Re: Responses to "Draft of charter for NextWebOnt (Proposed) Working Group"

From: Pat Hayes <phayes@ihmc.us>
Date: Sun, 14 Jan 2007 20:44:15 -0800
Message-Id: <p06230943c1d0b4454ac1@[]>
To: Dan Brickley <danbri@asemantics.com>
Cc: Jim Hendler <hendler@cs.umd.edu>, Kendall Clark <kendall@monkeyfist.com>, Uli Sattler <Ulrike.Sattler@manchester.ac.uk>, public-owl-dev@w3.org, Bijan Parsia <bparsia@cs.man.ac.uk>

>Pat Hayes wrote:
>>>At 5:02 PM -0500 1/12/07, Kendall Clark wrote:
>>>On Jan 12, 2007, at 1:15 PM, Jim Hendler wrote:
>>>  I would like to see one "OWL Ultralite" that is as close to RDFS 
>>>as possible
>>>I'd be happy to look at the model theory or axiomatization of such 
>>>a beast, if it's available. Not having seen anything yet, it's 
>>>hard to say whether it's interesting, either practically or 
>>>Kendall - you've seen the model theory!  This has been said all 
>>>along to be a subset of OWL, so the OWL documents provide the 
>>>model theory (and reference, and examples, and test cases, etc.)
>>Obviously (?) I would also be very interested in getting this 
>>right, also. But I think that rather than basing the model theory 
>>on OWL, the right way to do this is to follow the ideas developed 
>>by Herman ter Horst, who has written a lot on extending the RDFS 
>>style semantics. In particular, it ought to follow the RDF/S 
>>semantics in being non-extensional rather than the OWL insistence 
>>on extensionality: this gives a 'lighter' logic which is 
>>simultaneously more useful AND more tractable than a rigidly 
>>extensional logic. The pragmatic benefits of removing the 
>>extensionality condition have now been well validated (in a wider 
>>context) by the experience of using CL in the IKRIS project. 
>>Insisting that OWL be extensional was IMO a mistake, a good example 
>>of allowing theoretical 'elegance' to override useability 
>I'm intrigued. Are the IKRIS findings written up in detail anywhere? 
>Is http://www.ihmc.us/users/phayes/IKL/SPEC/SPEC.html a good place 
>to start?

No, to start the best place would be the GUIDE,


Appendix A is a long example all written as an IKL text.

Also there are some slides and even a recorded talk about it on the 
Ontolog Wiki




BTW, what I didnt mention above is that since CL makes everything 
into a function and also a relation, this applies even to things like 
character strings and numbers. Which even I thought was slightly 
insane and was planning to write exceptions into the semantics to 
rule this out, until we discovered to our complete surprise that 
allowing strings to be functions was critical to providing a uniform 
way to describe opaque name usages. I feel even more certain that 
designing a logical language with as few syntactic restrictions as 
possible is a very important design principle. You really never know 
when one man's lunacy is another man's (or even the same man's, a 
little later) really neat idea. All the matters is that the semantics 
is coherent and the syntax is usable.



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Received on Monday, 15 January 2007 04:44:34 UTC

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