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Re: Uniform access to metadata: XRD use case.

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 26 Feb 2009 11:52:49 -0600
Cc: <wangxiao@musc.edu>, <eran@hueniverse.com>, <julian.reschke@gmx.de>, <jar@creativecommons.org>, <connolly@w3.org>, <www-tag@w3.org>
Message-Id: <CDD92CF4-507E-4CEF-8AB6-EA7A0AE095CA@ihmc.us>
To: <Patrick.Stickler@nokia.com> <Patrick.Stickler@nokia.com>

On Feb 24, 2009, at 11:38 PM, <Patrick.Stickler@nokia.com> <Patrick.Stickler@nokia.com 
 > wrote:

>
>
>
> On 2009-02-25 02:00, "ext Xiaoshu Wang" <wangxiao@musc.edu> wrote:
>
>> The critical flaw of all the proposed approach is that the  
>> definition of
>> "metadata/descriptor" is ambiguous and hence useless in practice.   
>> Take
>> the "describedBy" relations for example.  Here I quote from Eran's  
>> link.
>>
>>      The relationship A "describedby" B asserts that resource B
>>      provides a description of resource A. There are no constraints  
>> on
>>      the format or representation of either A or B, neither are there
>>      any further constraints on either resource.
>>
>> As a URI owner, I don't know what kind of stuff that I should put  
>> in A
>> or B.  As a URI client, how should I know when should I get A and  
>> when
>> B?  Since I don't know what I might be missing from either A or B, it
>> seems to suggest that I must always get both A and B. Thus, I cannot
>> help but wondering why they are not put together at A at the first  
>> place.
>>
>> The same goes for MGET, how a user knows when to GET and when to  
>> MGET?
>
> If one wants a representation of the resource, use GET.

To avoid (even more) confusion, here you mean "representation" in the  
narrow TAG/awww sense. right? The sense used in the REST architecture  
description. Its important to get this clear, since when  
'representation' is used in its more common, wider, sense, a  
description _is_ a representation. In fact, descriptions are in very  
real sense the paradigmatic kind of representation.

> If one wants a description of the resource, us MGET.
>
> There is some potential conceptual overlap between representations and
> descriptions for certain kinds of resources, but the distinction  
> should be
> reasonably intuitive.

Actually no, its not _intuitive_ at all. Intuitively, in fact, it  
makes absolutely no sense whatsoever. Why is one special kind of  
representation, one that indeed has never been given a precise  
definition or any kind of semantics, and appears to have no precursors  
or exemplars anywhere in the entire technical literature previous to  
Roy's doctoral thesis, be elevated to such an exalted status that an  
entire world-wide transfer protocol be devoted to handling it, while  
ignoring all other forms of representation? And _how_ does this kind  
of representation make it fundamentally different from a description?   
Of course Im speaking intuitively here, and I think that both of these  
questions have reasonable answers: but AFAIK nobody has actually  
offered any; and they aren't particularly intuitive.

Pat
Received on Thursday, 26 February 2009 17:54:02 GMT

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