W3C home > Mailing lists > Public > www-webont-wg@w3.org > April 2002

RE: LANG, SEM: Re: more on a same-syntax extension from RDF(S) to OWL

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Mon, 1 Apr 2002 19:52:52 -0600
Message-Id: <p05101403b8bc94daf7b1@[]>
To: "Jeremy Carroll" <jjc@hplb.hpl.hp.com>
Cc: www-webont-wg@w3.org
>A small clarification,  and then a more detailed reply.
>Entailment & Logic
>>  Jeremy Carroll wrote:
>>  > What are the use cases for this ability?
>>  Basically anywhere you see (in N3) { ... } a context is defined
>>  in which the
>>  contents are not necessarily asserted.
>>  Perhaps the simplest use of this is an IF THEN statement or an OR
>>  statement
>>  IF {sky color blue} THEN {trees color green}
>>  A simple way to write down a simple formula is the use case.
>My problem with this is whether the examples are in scope.
>I am in this group to help provide a language to specify ontologies for data
>and information on the web.
>N3 and the examples appear to be trying the rather more ambitious task of
>having a web language for writing complex logical expressions. A worthwhile
>task, but not my understanding of our task.

Jeremy, perhaps you could clarify the distinction you have in mind 
here between 'data and information' on the one hand and 'complex 
logical expressions' on the other. I take it that you have in mind 
that the former does not require the latter, since it can be done 
using only 'simpler' logical expressions. Can you give, if only 
approximately, some idea of where you think the line should be drawn 
between the simple and the complex here?

>I believe that we will need to talk about logical entailment. (In order for
>us to discuss and specify the meaning of OWL).
>I do not believe that we will need logical entailment in our language.

If we have negation and disjunction then we are perilously close to 
having logical implication. And why not? Its very handy, 
three-year-old kids can understand it, and its almost impossible to 
specify ontologies without it in some form or another. Why are we 
going through such torture to avoid it?


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Received on Monday, 1 April 2002 20:52:55 UTC

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