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RE: Context Independent URI

From: Williams, Stuart <skw@hplb.hpl.hp.com>
Date: Mon, 22 Jul 2002 10:39:52 +0100
Message-ID: <5E13A1874524D411A876006008CD059F04A06F78@0-mail-1.hpl.hp.com>
To: "'Aaron Swartz'" <me@aaronsw.com>
Cc: "'www-tag@w3.org'" <www-tag@w3.org>

Hi Aaron,

> -----Original Message-----
> From: Aaron Swartz [mailto:me@aaronsw.com]
> Sent: 21 July 2002 22:25
> To: Williams, Stuart
> Cc: 'www-tag@w3.org'
> Subject: Re: Context Independent URI
> On Sunday, July 21, 2002, at 04:18  PM, Williams, Stuart wrote:
> > <principle>
> > ContextIndependentURI:
> > A URI SHOULD denote the same resource or concept independent of the
> > context(s) in which the URI is used. i.e. when used on different
> > or by different users or in different locations, a given URI SHOULD 
> > denote the same resource or concept.
> > </principle>
> Looks good. 


> You might want to emphasize the "resource or concept" bit 
> somewhere.

I'm hoping that this will come through in the rest of the architecture
document as we write it. One of the things that seems to give us some
trouble is describing quite what its is that a URI denotes. Personnally, I
quite like Roy's wording from [1]: 

  "...In other words, any concept that might be the 
   target of an author's hypertext reference must 
   fit within the definition of a resource. A resource 
   is a conceptual mapping to a set of entities, not 
   the entity that corresponds to the mapping at any 
   particular point in time."

It's this style of writing that motivated "resource or concept" rather than
one or the other.

> I know some people who are thrown off by this and think that 
> persistence and context-independence means it must always resolve to the 
> same kind of bit package. For example, a contextIndependentURI could 
> resolve to a set of nutrition facts and buying information in the 
> context of the supermarket but to cooking instructions in the context of 
> the home even though this seems a bit contradictory at first.

You might have to 'unpack' that a little more for me. 

I think it depends a bit on what the URI is intended to denote. I'm quite
comfortable with the bits changing either because the state of the resource
is different or, for whatever reason, a different representation of the same
resource/concept is presented on a different occassion.

*If* "nutrition facts and buying information" and "cooking instruction" are
reasonable representations of the same concept/resource... then I guess that
would be fine... but I'm trying to think what the 'super-concept' might be
that admits representation as "nutrition facts etc." or "cooking

> --
> Aaron Swartz [http://www.aaronsw.com] 
> 4FAC4838B7D8D13FA6D92EDB4145521E79F0DF4B
> I will be in San Diego for the O'Reilly Open Source 
> Convention the 24-26 
> July.


[1] http://www.cs.virginia.edu/~cs650/assignments/papers/p407-fielding.pdf
Received on Monday, 22 July 2002 05:40:26 UTC

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