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Re: resources and URIs

From: Norman Walsh <Norman.Walsh@Sun.COM>
Date: Thu, 31 Jul 2003 15:46:04 -0400
To: www-tag@w3.org
Message-ID: <87d6fq8ooz.fsf@nwalsh.com>

Hash: SHA1

/me still strives for closure on httpRange-14

/ Tim Berners-Lee <timbl@w3.org> was heard to say:
| As a web user. when I quote you
| http://www.galegroup.com/free_resources/poets/poems/kublakhan.htm
| What do I expect of this URI when I dereference it?
| 1. - That it is always something *about* stately pleasure domes?
| 2. - That it is always the poem "Khubla Khan"?
| 3. - That it is always a poem "Khubla Khan", as published in the
| Thompson/Gale collection?
| 4. - That it is always a particular set of bits?
| The answer is  2 or 3.  That is what we expect to be invariant for the
| URI.
| That is the basis on which I make hypertext links.
| That is the basis upon which URIs are used.
| That is why we say the URI identifies or denotes the poem.

Right, so I might say that it is the URI for the poem Khubla Khan, by
which I mean the poem as an abstraction, not the document that
contains the poem.

Does that square with your thinking on httpRange-14?

| I think that the word "representation"might have been historically
| unfortunate as it suggests "portrayal" (or a subject) rather than
| expression (of a message).


  1 a : an act, process, or instance of representing in a medium (as words)
     : UTTERANCE <freedom of expression> b (1) : something that manifests,
     embodies, or symbolizes something else

I'm not sure "expression" is going to help much if we're looking for
English language definitions that capture the distinction you're
looking for because in discourse we are quite able to use the symbols
without confusion.

I don't see why I can't say that http://norman.walsh.name/ symbolizes
me (I grant that it may not be the best choice of identifiers given
the ambiguity it introduces, but I can still do it.)

Consider the following conversation.

  John: That Norman is so clueless.
  Jane: Norman? Which one?
  John: http://norman.walsh.name/
  Jane: Oh, right. I thought you meant

Even though both of those URIs are "information resources" in your
world view and must be distinct from flesh and bone people, in
practice we don't have any trouble with using them as identifiers.

No matter what we say, some people will want to use identifiers that
way. The longer we talk about this, the more convinced I become that
the most we can possibly do is to explain why this might be a problem
and encourage people to avoid it unless they have good reason.

On the topic of good reasons, I was talking to Dan Brickley this
morning and he pointed out that WordNet[1] uses "/" instead of "#" in
identifiers. That's a case where I think the use of "/" is entirely
justified. It means that I can assign the WordNet URI to the "wn" prefix
and refer to wn:City, wn:State, wn:Person, etc.

If I used "#" instead of "/" it would be practically impossible to get
the RDF that described each word (it would mean downloading the
*entire* Word Net database as a single document and extracting the
relevant bit). Technically better, perhaps, but practically impossible
given the size of Word Net.

The fact that I can GET http://xmlns.com/wordnet/1.6/City and retrieve
RDF that defines "City" is so valuable, I'm quite willing to live with
the contradiction that if you choose to assert axiomatically that
http://xmlns.com/wordnet/1.6/City must be a document, you're saying
that the URI is both a city and a document.

                                        Be seeing you,

[1] http://xmlns.com/2001/08/wordnet/

- -- 
Norman.Walsh@Sun.COM    | It is a general error to imagine the loudest
XML Standards Architect | complainers for the public to be the most
Web Tech. and Standards | anxious for its welfare.--Edmund Burke, 1769
Sun Microsystems, Inc.  | 
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Received on Thursday, 31 July 2003 15:46:20 UTC

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