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Re: What do the ontologists want (what URIs denote)

From: Dan Connolly <connolly@w3.org>
Date: Tue, 15 May 2001 16:29:51 -0500
Message-ID: <3B019FCF.6412F2B9@w3.org>
To: pat hayes <phayes@ai.uwf.edu>
CC: Jonathan Borden <jborden@mediaone.net>, www-rdf-logic@w3.org
pat hayes wrote:
> >pat hayes wrote:
> >[...]
> >
> > > The relationship between a URL and the
> > > file it locates is not the same as that between a logical name and
> > > what it denotes
> >
> >Er... huh? To me, the whole premise of rdf-logic is that
> >the relationship between a URI (URL, if you like) *is*
> >the same as that between a logical name and what it denotes.
> I know that is widely accepted as a premis. I also think it is
> wrong,[later: see next para]  which is one reason why rdf-logic is in
> such a tangle. It is symptomatic of the general carelessness about
> use versus mention. The point of a URL in large part is that it
> provides an electronic route map to the thing it locates. What you
> get to is something that is readable and from which you might be able
> to make inferences, right?


What a URI denotes is an abstract resource; you cannot,
in the general case, directly observe it (i.e. you
can't "read" it); you can only indirectly observe it
by, for example, sending HTTP GET messages to it,
and having it reply with a representation of its state.

If it's a URI of the form NETADDR#NAME , you can't
even send messages to it; you can only send messages
to NETADDR; then you might learn about what
NETADDR#NAME denotes by interpreting some statements
that mention NETADDR#NAME (or more likely, its
short-form #NAME) in the response message.
(an agent may, of course, consult any other source
to find clues about the meaning

Just take as an axiom that the relationship between
a URI and a resource *is* the same as the relationship
between a logical name and what it denotes. Try it
on for size for a while.

> OK, so. Point taken. But then you have to fess up to the fact that
> the relationship between any kind of machine-processable inferencing
> and this standard interpretation has to be grounded in some
> non-logical machinery.

Yes, I've already fessed up to that...

The World Wide Web is a universal information space.
Informally, we discuss the Web as if it were frozen in
time and identical from all perspectives; we say that
"the title of http://www.w3.org/xyz is 'One Fine Day'"
despite the fact that the content---including the
title---of this resource may change over time, and
despite the fact that it may be available in French with
a different title. 

To specify the protocols that govern the Web, it is
essential to realize that in fact, the Web is a sort of
mass hallucination shared among all the people and
machines distributed around the globe who accept
the principles of Web Architecture, much the way
businesses and consumers accept the principles of an
economy based on paper currency. By and large, we
agree that there is one http://www.w3.org/xyz, even
though each of us has slightly different experiences
of it, much like by and large, people in the U.S. have a
shared concept of the value of a dollar, even though
in fact each person has a slightly different perspective
on what they're willing to trade for one. The large
scale effect is the result of each participant following
the same principles when they communicate and
interact with each other. 

When I say "the title of http://history.org/1492 is
'Christopher Columbus goes to America'," all I really
know is that my machine sent some packets to
history.org and get back some packets with HTTP and
HTML syntax that indicate a title of 'Christopher
Columbus goes to America' (and I only believe that
because I assume the machines didn't malfunction
and weren't tampered with). If you follow that
reference with your machine, you probably expect to
see the same title even though I don't guarantee it for
a fact. 

But your expectations are not the sort of "2+2=4"
certainty. Nothing prohibits the history.org
webmasters from setting up his server to return
completely random results in response to requests for
/1492. But why would they do that? They publish the
/1942 resource to participate in the network effects of
the Web, whose value depends on the fact that
following a link labelled "Christopher Columbus goes
to America" usually rewards the user with a resource
that is relevant to that subject. 

--        Web Architecture: Protocols for State Distribution
Fri, 17 Sep 1999 21:28:26 GMT

oops... that should say "... rewards the user with
a representation of a resource that is relevant
to that subject" or just "... rewards the user
with a document that is relevant to that subject".

I'm still working on that essay.

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 15 May 2001 17:29:54 UTC

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