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Re: Question on the boundaries of content negotiation in the context of the Web of Data

From: Xiaoshu Wang <wangxiao@musc.edu>
Date: Thu, 12 Feb 2009 16:59:43 +0000
Message-ID: <4994557F.4030800@musc.edu>
To: Jonathan Rees <jar@creativecommons.org>
CC: Michael Hausenblas <michael.hausenblas@deri.org>, "www-tag@w3.org" <www-tag@w3.org>



Jonathan Rees wrote:
> I don't mean to defend CN or any particular theory of documents, but
> here is how I've come to understand what Tim has said on the subject:
>
> Think about one of the canonical use cases, bookmarking. Abstract
> document (AD) = what you bookmarked = something satisfying the reason
> you bookmarked it = something that says what you expected it to say.
> That is, an AD is a set of expectations for its representations. I
> think this means that different purposes implies different ADs and
> therefore different resources. The different representations have to
> make a reasonable effort to be similar, because a visitor (one who can
> process all languages and media types in question) who bookmarked
> based on seeing one representation has to be happy when encountering
> another.
>
> A similar use case is you visit an AD in your browser, say "that's
> cool", email the URI to your friends with the statement "this is
> cool". You would be peeved if your friends went to look at it and what
> they saw was really lame, right?
>
> I don't think anyone would be happy if a .ttl were quietly substituted
> for a .png or vice versa. I bet it's possible to come up with
> particular .ttl/.png pairs where this might be possible (e.g. the .png
> is a scan of the .ttl), but I don't think your example is one of them.
>
> The idea seems to be inherently unformalizable, as it corresponds not
> to a set of testable requirements but to whatever would induce
> satisfaction among typical page re-visitors. I say "typical" because
> different visitors may be unhappy about different things. E.g. I may
> tell my friend to look at the top of page 7, and when my friend looks,
> all they see is HTML without page breaks; I'll be peeved because for
> me the PDF pagination had importance and I had no way to know CN would
> swap what I saw for something else. On the other hand if I had said
> look at section 4 I might not have cared about CN, if other
> representations preserved section numbering.
>
> Of course, if the URI owner has done nothing to set my expectations
> (e.g. say whether or not page layout is part of the resource's
> "identity"), I have no right to expect anything at all. [This is one
> reason I'm so interested in metadata protocols and formats: there
> needs to be a protocol and a language for communicating these
> expectations.] But people form expectations nonetheless, and that's
> why agreement is urged between representations.
>
> A good practice note might be in order, since the temptation to use CN
> in exotic and "lossy" ways that jeopardize bookmarking and casual URI
> sharing seems to be persistent.
>   
It depends what is the *expectation*.  Say, if I bookmark's Michael's 
house (though I expect it to be an image) and then I pass the *bookmark* 
to my agent (which say is RDF-capable) because I want someday the agent 
can help me to organize all the house that I have bookmarked.  Then, CN 
helps this cause because only one URI is found.  Otherwise, I must save 
myself a set of bookmarks and my friend (e.g., my agents) another one.  
To say that CN hampers search/bookmark is very ill-founded because it 
does the exact opposite.
> I'm as starved of citations on this subject as you are.
>   
I don't think that there is any such reference. But I would encourage 
you to read Quine's "Two Dogmas of Empiricism". Although it is a 
philosophical writing, but his discussion on analytic philosophy is very 
relevant to this topic because it resembles the debate about the 
distinction of information resource from those are not (and therefore 
httpRange-14).  Another very useful one is Fred Dretske's book 
"Knowledge and the Flow of Information". I am no philosopher, it is only 
the working on ontology and the httpRange-14 has forced me to start 
reading them because there is no other venues that can clear my mind.

As you talked about "expectation", a very important question that the we 
have to ask ourselves is:  Should the Web be designed/built to follow 
some particular expectation, or should it be designed/built in such that 
it can fit many kind of expectations, among which one (or a few) 
particular winner evolve?  I think, as evidenced by our natural and 
social history, it can only be the latter.

IMHO, the definition of Information Resource and therefore 
(httpRange-14) is the outcome of the first approach. Sure, someone can 
develop something based on the concept of information resource, but it 
should not be a core recommendation that prohibits other approach.  I 
have advocated many times in this mailing list to abandon the concept of 
information resource.  And I think that the one effect of abandoning it  
is, as Quine said in his article, a shift toward pragmatism.

Quine has famously said to let the science be the final arbitrator of 
truth.  I think, in the Web, we should let the real world applications 
be the final arbitrator of what the future Web is. 

Xiaoshu    
> Jonathan
>
>   
Received on Thursday, 12 February 2009 17:00:33 GMT

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