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RE: Section 2: What does a URI identify? (and range of HTTP deref)

From: Bill de hÓra <dehora@eircom.net>
Date: Tue, 26 Mar 2002 17:41:22 -0000
To: <www-tag@w3.org>
Message-ID: <003501c1d4ed$729e28f0$887ba8c0@mitchum>
 
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> -----Original Message-----
> From: www-tag-request@w3.org [mailto:www-tag-request@w3.org] 
> On Behalf Of Tim Bray
> Sent: 26 March 2002 01:24
> To: www-tag@w3.org
> Subject: Section 2: What does a URI identify? (and range of 
> HTTP deref)
> 
> 
> [Apologies in advance for verbosity.]
> 
> I've been thinking about whether or not a URI can identify a 
> car, and what resources are, and the REST notions of resource 
> and representation, and a few things float to the top:
> 
> When I am discussing actual Web software with actual 
> programmers and we 
> talk about pointing to things and designing address spaces, I
> always,  without exception, refer to Web addresses as URLs.
> 
> When talking about the theory of these things in the TAG and 
> other W3C contexts, I find myself always, without exception, 
> using the term URI. This is at least evidence of tension 
> between theory and reality.  
> 
> Let's take Roy Fielding's definition of a resource as 
> "anything that can be identified and which may have one or 
> more representations" 
> where a representation is some metadata (headers) and some bits.
> 
> It seems that there is a hierarchy of resource classes lurking in
>  here, whether or not we have the language to talk about them. 
> If we  did, it might be useful in writing down some things about
> the Web  architecture.

>> Tim Bray:
>
> The notion of "Mexico" can be identified, and I can write
> a URI and assert that it identifies Mexico:
> 
  http://www.textuality.com/countries/Mexico

and then write RDF rules about it and make inferences, and this
would be useful, but it would be unsurprising if the resource had 
no representations; and Mexico the nation will obviously transcend 
any individual representation.
>>

Wouldn't this work in reverse also? You have a URI to represent
Mexico and can use that URI to describe other resources as well as
say things about Mexico itself, for example a jpeg of Mexico,
whereas you're less likely to use the jpg URL you mentioned below
to describe something else.


>>
An example of another class of resource is that identified by

  http://www.xml.com/1999/12/graphics/connolly1resized.jpg

This resource has a representation.  In fact, I think this resource
*is* its representation.  (And I think that this 
URI is a URL, for what that's worth). 
>>

I'm not sure it is its own representation as it might change over
time. Isn't the data URI scheme used for resources that are
"inlined" as their own representation?

Bill de hÓra

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Received on Tuesday, 26 March 2002 12:53:17 GMT

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