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Re: The meaning of "representation"

From: Harry Halpin <hhalpin@ibiblio.org>
Date: Tue, 04 Dec 2007 16:21:01 -0500
Message-ID: <4755C4BD.4030603@ibiblio.org>
To: wangxiao@musc.edu
Cc: noah_mendelsohn@us.ibm.com, Chimezie Ogbuji <chimezie@gmail.com>, Mikael Nilsson <mikael@nilsson.name>, Tim Berners-Lee <timbl@w3.org>, www-tag@w3.org

Xiaoshu Wang wrote:
>>
>> No.  Assuming binary coding is used, the message is a sequence of
>> bits. It is presumed that the sender and receiver agree in advance on
>> the range of possible information values (my term, not Shannon's),
>> that a given message might convey;  each distinct message essentially
>> selects one of those values.    From Shannon's 1948 paper [1]:
>>   
> I take the 'no' means that the message is not embedded?
Noah's right - there's a a big difference between Shannon's theory,
about the reliability of transferring information via messages, and the
common-sense use of the word "information" which denotes something with
a meaning. Now what Tim means precisely, I'm not entirely sure of, but
there clearly a distinction between me and my web-page. It may not be a
rigid distinction, maybe more of a continuum, but there's likely a
distinction. You might want to look into Dretske, who investigates the
"semantic theory of information" (which does end up being subjective).
See my notes [1] if interested.
> I snip the rest (to shorten the message) because I agree your
> interpretation of Shannon's theory. However, I disagree that the
> assumption that the number of messages, with regard to a URI's
> representations, is finite. In principle, I can use ONE bit message in
> conjunction with various content types to answer all your questions
> about the resource. From a communication point of view, a user do not
> have a pre-established context with the resource.
At a given time it would seem that the number of possible
representations returned by a URI is finite. And the user does have a
pre-established context with the resource, via the standards implemented
by the browser, etc. etc. It may not completely determine the
interpretation of the resource as regard a human user (although it might
for a computer), but then....nothing does in any sort of communication
when humans are involved.
> Second, even if the context is set, it still does not mean that the
> resource is 'information'.  IMHO, Shannon's theory is to study the
> capacity, but not the meaning, of information. But in semantic web, we
> only care the latter. Meaning is to be understood - to be processed,
> by our brain or by computers. Without this process, nothing can become
> information.
Again, Noah's right re Shannon, and you're using the "common-sense" use
of the word, which has no coherent definition (see Wikipedia[2], which
explores some of these meanings and differentiates them).

[1]http://www.ibiblio.org/hhalpin/homepage/notes/explainingdretske.html
[2]http://en.wikipedia.org/wiki/Philosophy_of_information
> Xiaoshu 


-- 
		-harry

Harry Halpin,  University of Edinburgh 
http://www.ibiblio.org/hhalpin 6B522426
Received on Tuesday, 4 December 2007 21:21:24 GMT

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