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Re: article on URIs, is this material that can be used by the SWEO IG?

From: John Cowan <cowan@ccil.org>
Date: Thu, 31 May 2007 03:57:31 -0400
To: Pat Hayes <phayes@ihmc.us>
Cc: www-tag@w3.org
Message-ID: <20070531075731.GG11862@mercury.ccil.org>

Pat Hayes scripsit:

> OK, fair enough. But then it follows that there is nothing 
> *intrinsic* to that resource that makes it be a subject indicator for 
> Shakespeare. It is so simply because you say it is.

Just so.

> But when I read that resource, how do I gain access to *your* intention
> that it shall be a subject indicator? What readable resource is it that
> tells me that http://en.wikipedia.org/wiki/Shakespeare is a subject
> indicator for Shakespeare ?

You can't in any absolute sense: you have to triangulate from
published subject indicators -- which, remember, contain an assertion
by the publisher of the resource; this assertion must be present in
human-readable form, and should be present in machine-readable form as
well, in the representation of the resource.

> >Two resources identified by the same subject identifier (or
> >in fact with the same subject-indicator-reference URI)
> >are the same.

(s/identifier/indicator/, of course)

> How can a single URI identify two different resources?

It can't, of course.  What I meant is that if two graph nodes share a
subject indicator, they are treated as the same node: the assertions
attached to them may be merged.

> But it is trivial to predicate about grains of sand on a beach. The 
> sand on Pensacola beach, every grain of it, is made of quartz, and so 
> the beach is pure white. There: in the previous sentence I asserted a 
> predication of every grain of sand on a beach. So, do all those 
> grains now have an identity?

Not really, because the grains are indiscernible except in the inert
property of location: any grain can be substituted for any other without
anyone being one bit the wiser.  Which grain is which is what Dennett (I
think) calls an inert fact; one which is clearly either true or false but
make no difference at all to anyone about anything.  Either such-and-such
a dust-mote was once part of Alexander the Great or it wasn't, but
so what?

> Of course there was. It was in pipes rather than in the cup, and it 
> had a different shape, but it certainly existed. If the pipes are 
> contaminated with lead, you had better not drink the water in the cup.

Or any other water from those pipes: again, all water-blobs from
those pipes are indiscernible except by inert facts.

> "Useful" opens up a whole new can of worms. Im not particularly 
> interested in useful identities: I just want to know what it means to 
> say that something has (and that something else lacks) an identity of 
> any kind.

"No entity without identity."  It's the identity criterion that divides
the world into *objects* at all.

> That person would not be Shakespeare. Is that all you mean by your 
> phrasing? Or does your use of "identified as separate" imply 
> something other than simple inequality? 

To say that Bacon is not Shakespeare means (among other things) that
Shakespeare has an identity and so does Bacon.

> as presumably if a person is indeed unknown, then 
> surely he or she is not identified at all (??)

When we say someone is unknown, we don't usually mean that *nothing*
about them is known.  Between 1814 and 1827, many people knew that
the author of _Waverley_ was also the author of many other novels,
but only a few could identify him as Walter Scott.

> After all, we can be fairly sure that Shakespeare is not, say, my
> toaster oven: but that fact about him is not usually thought of as
> "identifying" him as "separate from" my toaster oven. How does this
> case differ from your example?)

It doesn't.

> Why do I know that? For all I know, Willem de Kooning might be a nom 
> de plume for Rauschenberg. 

Perhaps the example was poorly chosen.  As is easily discovered,
de Kooning is dead and thus cannot be a *contemporary* artist.

> But in any case, you havn't answered my 
> question. Is *any* fact about a thing enough to give that thing an 
> identity? It would seem to follow that everything has an identity, 
> since we know some facts about every thing (such as that it is equal 
> to itself).

Such facts, however, are general properties or else inert facts.

-- 
But that, he realized, was a foolish            John Cowan
thought; as no one knew better than he          cowan@ccil.org
that the Wall had no other side.                http://www.ccil.org/~cowan
        --Arthur C. Clarke, "The Wall of Darkness"
Received on Thursday, 31 May 2007 07:57:48 GMT

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