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Re: Terminology (was Re: article on URIs, is this material that can be used by the)

From: Pat Hayes <phayes@ihmc.us>
Date: Tue, 26 Jun 2007 15:20:44 -0500
Message-Id: <p06230903c2a71c78cb11@[]>
To: noah_mendelsohn@us.ibm.com
Cc: Dan Brickley <danbri@danbri.org>, "Henry S. Thompson" <ht@inf.ed.ac.uk>, Pat Hayes <phayes@ihmc.us>, Tim Berners-Lee <timbl@w3.org>, www-tag@w3.org

>Like Henry Thompson, I've never felt that the English word
>"representation" suggests either completeness or full fidelity.

I agree there, since the meaning of that word encompasses 
descriptions, which are always incomplete in some respect.

>  Indeed,
>had the history of the Web been a bit different, I personally would have
>had no objection to allowing retrieval of "representations" even of
>tangible objects that are not what we now call information resources.
>Although an information resource >can< be represented with full fidelity
>in a message, we clearly allow for less than full representations anyway,
>even with a 200.  For example, I think it's OK to conneg between image/gif
>and image/jpeg for the same photo, yet almost surely at its native
>resolution GIF will preserve detail that jpeg doesn't, but when zooming
>most viewers would feel that jpeg remains truer to what is (presumably)
>the photograph itself.  We also allow for foreign language translations of
>text information resources, even though those almost surely lose some
>nuance.  So, even in the Web as deployed today, is precedent for
>representations of information resources being incomplete or otherwise
>imperfect.  In principle, I would think we could have representations of
>concrete objections as well.
>However, I have come to believe that:
>* The distinction between information resources and non-information
>resources is a useful one.

Agreed, even though it is not exactly well-defined. But the key 
distinction, which this one is obscuring, is between access and 
reference. As long as this basic distinction is muddled, this issue 
will not go away no matter how many ingenious hacks are invented to 
try to get around it.

>* Having HTTP GET indicate in the results of an interaction whether what
>has been contacted is in fact an information resource, and thus whether
>the representation stands in the sort of relationship to the resource that
>we expect for information resources (which >can< by definition be
>faithfully sent in message), is useful.

There I disagree. Your locution here reveals the essential point. 
"the sort of relationship to the resource that we expect for 
information resources". WRONG. In fact, I expect to have at least TWO 
distinct relationships to information resources. I expect to be able 
to access them, using some kind of xxxTP protocol, AND I expect to be 
able to refer to them. Referring to them is exactly like referring to 
anything else: the same relationship is involved, the same semantic 
theories apply, and the same inference processes can be used for 
referential languages. When referring, the nature of thing referred 
to is almost irrelevant, in fact. The distinction between kinds of 
resource matters only because non-information resources can't be 
accessed. But if we distinguished between reference (naming) and 
access (as we should have been doing since day one and as everyone 
did before the W3C - in what is surely one of the most regrettable 
mistakes since the founding of the Holy Roman Empire - confused URLs 
and URNs into a single category) instead of calling them both 
'identify' and insisting that they are the same relation, then we 
wouldn't need to be having this damn silly discussion.

>* We should respect the precedent that's been established for signalling
>this, which is to use HTTP status code 200.

As I understand the proposal (it may have been revised recently) it 
does not do that. What it signals, rather, is that the resource may 
or may not be an information resource: that is, that its being a 
non-information resource is POSSIBLE. In the proposal as originally 
stated, there is no mechanism for signalling that any resource is 
definitely a non-information resource.

>So, I would have not have had objections in principle if the Web had done
>this differently, but I think the path we're on is OK.

I think it is a disaster. It provides no useful functionality where 
it might be useful, it is predicated on a fundamental theoretical 
error (the conflation of identification with reference), and it is 
poor engineering, since it mis-uses part of the basic Web 
architecture for an alien purpose for which it is not well suited. It 
requires what should be a textual matter to get involved with 
network-traffic code. It is in fact a kludgey hack.

>  200 means
>information resource.

I don't think this is accurate, see above.

>  We now have to establish best practice in the case
>that it's a non-info resource,  which is what the TAG is lately


>Noah Mendelsohn
>IBM Corporation
>One Rogers Street
>Cambridge, MA 02142

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Received on Tuesday, 26 June 2007 20:21:11 UTC

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