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Re: [ontolog-forum] RDF & RDFS (was... Is there something I missed?)

To: ian@xxxxxxxxxxxxxxxx, "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Wed, 4 Feb 2009 15:43:59 -0600
Message-id: <2C5FFB90-E9C0-474F-BE33-70C487452CF1@xxxxxxx>

On Feb 4, 2009, at 3:07 PM, Ian Bailey wrote:

Hi Ed,

Sounds like we agree (well, you make sense to me, even if I don't to you),
it's just my understanding of "ontology" and "semantics" differs from yours.

To be fair to Ed, your understanding of these terms differs from the meanings we had agreed, after exhaustive discussion, to adopt for use in this forum. 

My "ontology" is my model of the world, and I don't care how it's
represented so long as I know how the symbols in the representation map onto
the things in my ontology (those are things whose extent is identified).

Speaking from the ontology engineering perspective, this is a fine claim to make, except it cannot be cashed out in anything real. Although we would all ike to think that we have a complete mental model all done up ready for use in our own heads, and writing axioms is just formalizing it, this isnt borne out by experience. The very act of writing down ones intuitive knowledge as formal sentences reveals aspects of your own thoughts which weren't apparent before, and also of course you rapidly find that a lot of what you know simply can't be written down properly. So the process of writing down intuition is more like a process of invention or composition - guided of course by the intuition, but one which itself alters the intuition as it is performed. So-called "knowledge extraction" is more like a writing a book than having your hair cut.

is essential that the representation is computer interpretable, as
interoperability is the goal of IDEAS - still doesn't rule out barcoded body
parts, you'll note. 

I still can't see RDFS and RDF as anything other than syntax (sorry, we
might have to disagree on this)

You are simply wrong about this. I'm not pulling rank or anything, but RDF/S is pretty tightly described in the W3C specs, which are quite clear on what parts are normative, and the model-theoretic semantics is normative. So for example if you say that rdfs:subClassOf is just syntax, so you will choose to interpret it as the motherOf relation, then you are not using RDFS. You are using RDFS syntax in some other, non-RDFS, way. 

. However, as long as I document how that
syntax maps to the concepts in the ontology, it's OK with me.

Also, you wrote:

"I think Barry's point is that your IDEAS RDF language is so massively
extended and possibly so weakly defined with respect to interpretation
semantics that no one, including you, has any idea what kind of reasoning
engine could actually process it in a non-trivial way."

I don't think Barry Smith has looked at IDEAS. My point was about his
critique of ISO15926 (http://ontology.buffalo.edu/bfo/west.pdf). If you can
use something as arcane as EXPRESS (and Part 21/28) to model your ontology,
then bending RDFS to represent an extensional ontology really ought to be
kosher ! I agree though, that you have to be crystal clear about how the
RDFS elements map to the ontology.

Another clarification is probably needed. I only mentioned reasoning because
projecting to a 1st order representation is one useful work-around for
making a higher order ontology tractable.

You might be interested in looking at Common Logic, which takes this idea and tweaks it into an entire logic, allowing arbitrarily 'higher-order' syntactic constructions within a strictly first-order logic, with no work-arounds needed. And I don't know if you have noticed, but RDFS uses the same trick. (OWL-DL doesn't, but RDFS does.)

The world is higher order, so we
decided to make the IDEAS ontology higher order. If the level five wizards
want to roll their 36-sided dice of inference, then I see no reason (groan)
to spoil their fun.

My God, are you still playing D&D? You need to move up to WOW. 

Pat Hayes

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