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Re: homonym URIs (Re: What if an URI also is a URL)

From: Ian Davis <lists@iandavis.com>
Date: Wed, 13 Jun 2007 23:57:32 +0100
Message-ID: <4670765C.3070506@iandavis.com>
To: John Black <JohnBlack@kashori.com>
CC: Pat Hayes <phayes@ihmc.us>, Sandro Hawke <sandro@w3.org>, semantic-web@w3.org

On 13/06/2007 14:10, John Black wrote:
> Please forgive me, Ian, I'm going to highjack this for myself.
By all means :)

I wrote:

>> Out of interest how do you attach the English word "Venus" to the 
>> physical body that you are referring to?

To which you part of your reply was:

> When I write the word Venus, I do it expecting you, my readers, to have 
> had similar experiences to me. I expect you studied the planets in first 
> grade, have access to WikiPedia, can clearly see the sky, that some 
> trusted elder spoke the word "Venus" and pointed your attention to a 
> bright light in the sky, etc., etc. Also, if I know that there may be 
> confusion, because the word can be ambiguous, I may add to the dance 
> with a little jig, as in, "I think Venus, the planet, is wonderful." If 
> I have already established the context, however, I may count on you to 
> disambiguate it yourself. In a report about the planets of our solar 
> system, I expect you to infer yourself that I mean Venus to refer to the 
> planet, not the tennis player.

This is what I expect and it makes its point very well. My question was 
somewhat rhetorical to test whether I understood the debate adequately. 
I think I do now.

> Restoring some of Pat's remarks, "The only way out of this is to 
> somewhere appeal to a use of the symbolic names - in this case, the IRIs 
> or URIrefs - outside the formalism itself, a use that somehow 'anchors' 
> or 'grounds' them to the real world they are supposed to refer to."

This is the bit I don't understand. I'm not a logician nor a philosopher 
so I'm applying the little common sense I have to this problem. It seems 
to me that there is no difference here between the symbol 
"http://example.com/venus" and the symbol "venus" (being the word I 
would utter in conversation). Neither can be attached to the physical 
object that they refer to. However they can both be understood by 
relating them to other symbols.

In my naive view of human cognition, I imagine that you and I can 
negotiate a shared meaning of a symbol by relating them to many other 
symbols to the degree that really only a single thing can be the 
referent. My conceptual graph of relations between symbols is isomorphic 
to yours so the thing at the heart of that graph must be the same as yours.

Clearly this is easier when you are able to indicate the referent of a 
symbol by pointing to it, e.g. an apple on a tree. However in the 
semantic web we only have a single sense with which to relate things 
together. It's like sharing knowledge with someone when neither of you 
can see, taste, feel or move.

> What he is calling "...outside the formalism itself...", I am referring 
> to as shared experiences, following John Dewey, and which Herbert Clark 
> calls common ground, Kripke calls a name baptism, and Searle refers to 
> as the background.

OK, this is new stuff for me, but it seems to me that it's like pointing 
to the apple in my example above.

> So the big, big question, IMHO, for the semantic web is this. What can 
> be done to mimic, in some minimal, but sufficient way, using existing 
> web technologies, in a way that machines can utilize if possible, the 
> grounding of URI in something outside the formalism of RDF/OWL/etc.?

Isn't that where humans come in? Your RDF states that a particular URI, 
when dereferenced using HTTP, provides a depiction of an apple. I try 
that, see an apple and conclude that I now understand the meaning of 
your URI (it may take a while if I don't understand your property).

The following metaphor came to me while writing the above about having 
only a single sense. I wonder if it helps illuminate why I think the 
semantic _web_ is different to the world of semantics that came before:

Imagine you and a stranger can only communicate through the use of 
coloured pebbles that you may place in various arrangements. Suppose 
this stranger arranges a crimson pebble between a yellow pebble and a 
blue one. Next they place another crimson pebble next to the blue one 
and a white one next to the new crimson one. Then they place a brown 
pebble next to the blue one and a grey one beside that. Finally they 
place a green pebble and a black one with yet another crimson pebble 
between them.

You start to see a pattern forming. Somehow the crimson pebbles link the 
other pebbles together and you suspect it represents some common 
relationship. However, since you can only communicate in coloured 
pebbles you can never relate that to the rest of the world.

Now, suppose you learn that you can turn the pebbles over. You turn the 
yellow pebble over and discover a picture of a young Elvis painted on 
it. You turn the white one over and discover a picture of an older 
Elvis. You turn the blue pebble over and there's nothing on the other 
side. The same is true for the crimson pebble. When you turn the grey 
pebble over you see the number 1935 inscribed on it.

Now you turn to the second arrangement of pebbles. Under the green one 
is a picture of Bill Haley. The crimson one is blank, as is the black one.

Perhaps you might infer that the red pebble somehow denotes "picture", 
although with this limited evidence there are many other possible 
explanations. The more arrangements of crimson pebbles touching pebbles 
with pictures on the back you see, the more confidence you might gain 
that the crimson pebble denotes "picture". Even more so if you have no 
contradictory evidence. At some point you may even infer that the blue 
pebble denotes Elvis Presley.

Turning the pebbles over is grounding it in the real world; in your 
human experience.

In the Semantic Web the equivilent of turning the pebbles over is 
dereferencing a URI. For HTTP URIs, we perform a GET. A human can do it 
to discover what a URI denotes and by looking at lots of these patterns 
they can gain confidence in their interpretations of the URIs that 
denote the relationships between these things.

That's how I see the Semantic Web.

Received on Wednesday, 13 June 2007 22:57:50 UTC

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