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Re: resources, stuffs and individuation

From: pat hayes <phayes@ai.uwf.edu>
Date: Wed, 23 Apr 2003 22:12:33 -0500
Message-Id: <p0521060dbacd022907de@[10.0.100.12]>
To: Michael Mealling <michael@neonym.net>
Cc: uri@w3.org

>On Wed, 2003-04-23 at 19:13, pat hayes wrote:
>>  >>... so how about "a resource is anything that can be referred to".
>>  >
>>  >It is synonymous with "a resource is anything that can be identified",
>>
>>  That wasn't my intent. One may be able to refer without identifying,
>>  which was part of the point. Also, I know what 'refer' means much
>>  better than I know what 'identify' means. It carries less baggage.
>
>How can you 'refer' to something if you have no way of talking about
>things outside your knowledge other than by a URI?

For example, by making assertions, using some URirefs, which can only 
be true if some things exist, without saying what those things are 
exactly. Database reasoners and description-logic engines do this all 
the time, eg something might know that Joe (who has a URI, let us 
say) has three sons one of whom works for Boeing (which has a URI, 
say), but may have no URIs for the sons in question.  The 
intelligence community uses software which makes inferences like 
this, for one example (see the slides at 
http://www.daml.org/meetings/2001/07/pimeeting.html for example), and 
so do many industrial applications. There is an entire industry 
revolving around DL-type inference models and rule inference systems, 
and these formalisms all have referential semantics as part of their 
interoperability specification. There are formalisms defined already 
by the W3C which use URIs to refer, according to semantic rules 
published as part of the spec of the formalism.

>I assume that to
>'refer' to something requires some kind of language for doing so?

Yes, and the languages which concern me are those defined by W3C specs.

>RFC 2396 and URIs have to work and be useful regardless of whether or
>not some specific system can 'refer' to things via some other mechanism.

Im not talking about mechanisms, but about the semantics of formal 
languages; and there is no need for the scare quotes, by the way.

>I think its useful to point out again that URIs have to work for all
>past, present and future systems. That includes things that you would
>consider 'on the web', and ones you wouldn't. (My definition of the web
>is the set of all RFC-2396-Resources but that's not a common definition
>these days). That includes the Semantic Web as well as LDAP, Web
>Services as well as VOIP, sip, pop, tip, telnet, etc.

I understand, and agree.

>
>That means that URIs have to work even in the case where two systems
>have lethally incompatible models of reality.

I agree that there are potential problems here.  (There are some 
slides under 'UWF' at the above website on this very topic, with the 
title 'when ontologies collide') In fact, any statement to the effect 
that URIs must identify a unique entity, for example, already produce 
such lethal incompatibilities. Which is why I was asking for 
clarification in the first place.

>To me that means that
>RFC2396bis should say as little as possible.

Well, I agree with you there.  But 'identify' says a hell of a lot 
more than 'refer'.

>Concepts such as 'refer'
>don't belong in there at all.....

It just means, designate or identify or indicate or denote or 
represent.., ie somehow be interpreted to indicate something, in the 
most general sense possible; that is, with as few extra impositions 
of meaning as possible.

Pat Hayes

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Received on Wednesday, 23 April 2003 23:12:36 GMT

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