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RE: Denotation of URIs

From: <Patrick.Stickler@nokia.com>
Date: Fri, 11 Apr 2003 13:04:07 +0300
Message-ID: <A03E60B17132A84F9B4BB5EEDE57957B5FBB83@trebe006.europe.nokia.com>
To: <dehora@eircom.net>
Cc: <pfps@research.bell-labs.com>, <www-rdf-interest@w3.org>

> -----Original Message-----
> From: ext Bill de hÓra [mailto:dehora@eircom.net]
> Sent: 11 April, 2003 12:21
> To: Stickler Patrick (NMP/Tampere)
> Cc: pfps@research.bell-labs.com; www-rdf-interest@w3.org
> Subject: Re: Denotation of URIs
> Patrick.Stickler@nokia.com wrote:
> > If researchers want to grapple with the problem of ambiguity of
> > denotation in knowledge bases, fine, but ambiguity should not be
> > considered an acceptable characteristic of the SW architecture and
> > should be guarded against, flagged, and fixed always.
> Certainly, but it is unwise to expect it can be eradicated.

I agree. Show me anywhere in my posts where I said it *could* be

My assertion has simply been that ambiguity is bad. Not that it
can't or won't occur.

I can say the same thing about murder or rape. They are bad. But
saying they are bad does not mean they won't occur.

And if someone tells me that because murder and rape are part of
the real world, so we should just accept it and tolerate it, I'll
have the same response for them that I have for those saying the
SW should accept and tolerate ambiguity of URI denotation: 

  "Definitely not, and what planet did you say you were from?"

> > Ambiguity of denotation on the SW will *always* be detrimental.
> But to think it won't be there or can simply be architected out of 
> existence is simpleminded positivism.

And how exactly does that statement reflect simpleminded positivism?

I consider those who are unnable to differentiate between calling
something bad and saying it can't exist to be the simple minded

Please, let's try to avoid any name calling. Eh?

> > Ambiguity of URI denotation on the SW will happen, but will 
> always be bad.
> My objection to your opinion is this: a semantic web system that 
> can't or won't deal with ambiguity and prefers a perscriptive rather 
> than descriptive approach is consigned to being a toy system. IMO, 
> history bears this objection out. Insisting that the entire domain 
> of the semantic web be a toy isn't going to have a happy ending. I 
> hope at least we can learn *something* from 50 years of AI research.

On the contrary, I think that if SW agents cannot presume that 
when they say things using URIs that those URIs denote the same
things for both agents, then the SW is doomed to failure as there
will be no basis for reliable communication.

> I feel an 'eight fallacies of the semantic web' is needed.

Yes. And add as one of them the fallacy of presuming that ambiguity
of denotation is acceptable.

> > But there are different ways of dealing with it. One can presume
> > unambiguous denotation and when one gets undesirable/unreliable
> > results from a SW reasoner, one can identify the source of the
> > the problem and either correct it or exclude that source from 
> > ones reasoning due to being unreliable/untrusted.
> It's good that we're recognizing the need to keep people in the 
> reasoning loop, to deal with the ambiguity. So, I wonder whether we 
> have any idea if housekeeping these knowledge bases is a viable 
> task. Should we expect a rehash of the expert systems debacle? Or 
> perhaps Forbus and De Kleer will become a deserved best seller if 
> they port their code to Perl ;)
> > The SW agent itself need not have any other presumption but that
> > URIs have unambigous denotation.
> That makes total sense. 

Didn't you just called me simple minded for holding this view ;-)

> The problem with the current architecture is 
> that it has no layer in its cake for distribution of denotations. 

Why should it? URIs are atomic primitives of the SW. The whole point
is that you have a foundational layer that you don't *have* to go
below. URIs denote resources and the unambigous, globally consistent
denotation of resources is a premise of the SW archtecture (or at
least of mine ;-)

To posit machinery for the specification of denotations is simply
to push the SW architecture down a level needlessly, since you
are *still* going to need atomic primitives at that lower level.

Hey, if someone wants to go and try to define some universal
semantic primitives by which all things in the universe can be
reliably described and thereby be able to specify the denotation
of URIs with a minimal vocabulary of atomic primitives, more power
to them. 

Pardon me if I don't hold my breath...

> There's RDF on the web, magic happens, and out comes a graph. This 
> unfortunately involves URIQA, which without architectural guidance 
> is a patch. 

I don't see it as a patch. I see it as an enabler, allowing existing
web servers to provide descriptions of resources in addition to
representations of those resources.

> I think that speaks quite badly of the architecture, 
> rather than your program, which I'm really looking forward to.

Well, trying to integrate the Web and SW is not IMO going to 
be as straightforward as some folks seem to presume, at least
not if we are limited to the existing Web machinery.

URIQA takes an approach similar to WebDAV, providing additional
verbs which have metadata specific semantics.

I hope to be able to release the first version of URIQA in a 
week or so.

> > I guess time will tell which position is correct.
> We don't need to wait to find that out - being correct is 
> irrelevant. Utility is king in a complex system. It's evident that 
> inference engines are inadequate for complex environments - they 
> require filters to makes sense of the world. Layered architectures 
> derived from robotics, insects and search engines are much more 
> useful than inference engines and theorem provers or handwaving 
> about architecture. As a matter of fact, the scruffy approach is 
> already winning the argument, without resorting to five year plans - 
> any ability to do logical inference with symbols is simply a useful 
> optimization to a system predicated on statistical processing. And 
> the chances are most of things people will want to do with the 
> semancic web will tolerate a level of ambiguity that makes building 
> the damn thing cost-effective. Anyone who needs more precision will 
> have to pay for it, that's how engineering works.

I don't disagree with anything you've just said, nor do I think any
of my posts contradict it.

Your use of the word "tolerate" simply emphasises the fact that
ambiguity of denotation is not a good thing. Good things are not

> > Then I think that you and I will not be using the same semantic web.
> Yes, you'll be using a subset.

I like to think I will be using the SW and Peter, and those wanting
to (for whatever insane reason) accept arbitrary ambiguity of denotation
will be using a superset of the safer, more consistent, reliable, useful
(albeit surely imperfect) SW.


Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com
Received on Friday, 11 April 2003 06:04:11 UTC

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