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Re: More on distinguishing information resources from other resources

From: Roy T. Fielding <fielding@gbiv.com>
Date: Tue, 28 Jun 2005 19:32:12 -0700
Message-Id: <42361eafd510928ce9bff306ee332ede@gbiv.com>
To: www-tag <www-tag@w3.org>

Please join me in a chant of "It just doesn't matter."

We could spend a great deal more time trying to precisely define
the meaning of "information resource", and yet doing so solves
no known problem in the architecture.  The goal of the resolution
is to provide a way to supply information about a resource that
is not actually "representable" on the Web, where representable
is entirely dependent on what the owner of that URI intends it
to identify, and yet do so in a way that would allow the
Semantic Web to distinguish between the resource identified by
the URI and the other resource providing the description.

In short, it licenses the Semantic Web to consider a 200 response
to GET to be indicative of a representable resource, whatever
that means, while describing how to provide information about a
non-represented resource at minimal extra cost to the old Web.
Whether this distinction actually turns out to be needed or not
is besides the point -- simply defining it solves the semantic
problem at minimum cost and allows us to get back to describing
how the system works rather than what resources mean.

Whether a given resource should respond to GET with a 303
instead of a 200 is entirely dependent on the intentions of
the URI owner and entirely under the control of that owner,
so there is no need for us to talk about it any further
beyond what we have already noted: a URI should only be used
to directly identify a single resource.  In other words, 303
should be sent when the owner thinks the requested resource
is not, for whatever reason, represented directly, though
information about it can be obtained from the other resource.

When a URI does get used in an ambiguous manner, the SW now
has a defined algorithm for disambiguation that will allow it
to note such errors accordingly. When a purely conceptual
resource is identified using a URI, the hypertext Web can still
be used to follow the chain of links to provide more information
about the resource without causing ambiguity.  Everyone wins.

Cheers,

Roy T. Fielding                            <http://roy.gbiv.com/>
Chief Scientist, Day Software              <http://www.day.com/>
Received on Wednesday, 29 June 2005 02:33:10 GMT

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