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[ontolog-forum] RDF theory vs. practice

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
Cc: KR-language <kr-language@xxxxxxxxxxxxxxx>
From: "Richard H. McCullough" <rhmccullough@xxxxxxxxx>
Date: Fri, 11 Apr 2014 00:10:50 -0700
Message-id: <COL129-W136809FD8473FD782A3880CB540@xxxxxxx>
This is the tail-end of a dialog between  Pat Hayes and me.
I think it may interest members of Ontolog Forum.
Dick McCullough
Context Knowledge Systems
mKR/mKE tutorial

From: rhmccullough@xxxxxxxxx
To: phayes@xxxxxxx
Subject: RE: reset: RDF semantics
Date: Wed, 9 Apr 2014 22:06:47 -0700

I completely agree with you, Pat.

As I mentioned in one of my other emails, I tried very hard to maintain
that the element and the set should  be distinguished.
I referred to element as a unit, or an individual.
I referred to the set as a concept or a Class.
But EVERYONE I came in contact with [before Ontolog Forum],
all the people actually using RDF, insisted that they were the same.

That is even the position of Adam Pease, who got very upset when
mKE/mKR told him he had errors in the SUMO knowledge base --
saying that a particular Name was an individual and a Class.
He insisted that his reasoning program [I can't remember the name]
verified that there were no errors.

It is legitimate to have the same Name
represent a unit in one context,
and a concept in another context.
Unfortunately, people want to "take the easy way out":
ignore the context and pretend everything is a concept.

Dick McCullough
Context Knowledge Systems
mKE and the mKR language
mKR/mKE tutorial

> Subject: Re: reset: RDF semantics
> From: phayes@xxxxxxx
> Date: Wed, 9 Apr 2014 22:31:28 -0500
> To: rhm@xxxxxxxxxxxxx; rhmccullough@xxxxxxxxx
> On Apr 9, 2014, at 10:17 AM, Richard H. McCullough <rhmccullough@xxxxxxxxx> wrote:
> > step 1. given
> > (1a) you do not distinguish element from set containing only element,
> Ah, but you should. In fact, if you are thinking of these classes as sets (as in set theory) (which RDF does, basically - strictly, the class *extension* is a set) then you *must* make the clear distinction between x and the singleton class of x (ie the class whose only element is x, let me write this as {x} ), because they have different properties. For example, suppose x is not a class; then since {x} is a class, they can't be the same. But you think that everything is a class, right? OK then suppose x is a class with more than one element, say the class of all human beings. Then x has many elements but {x} has only one element, so again they can't be the same thing.
> Pat


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