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Re: Issue-57

From: Tim Berners-Lee <timbl@w3.org>
Date: Sat, 25 Jun 2011 18:42:18 -0400
Cc: Xiaoshu Wang <xiao@renci.org>, Jonathan Rees <jar@creativecommons.org>, Alan Ruttenberg <alanruttenberg@gmail.com>, David Booth <david@dbooth.org>, Jeni Tennison <jeni@jenitennison.com>, "www-tag@w3.org List" <www-tag@w3.org>
Message-Id: <6CB64320-9D52-4314-A81C-D772BE57520E@w3.org>
To: Ian Davis <lists@iandavis.com>

On 2011-06 -25, at 06:37, Ian Davis wrote:

> On Sat, Jun 25, 2011 at 8:18 AM, Tim Berners-Lee <timbl@w3.org> wrote:
>> 
>> On 2011-06 -24, at 22:24, Xiaoshu Wang wrote:
>>>> Can I use that URI for statements about a picture?
>>>> Can I use that URI for statements about Barak Obama?
>>>> for example.
>>> 
>>> Yes, either way is fine.
>> 
>> 
>> In that case, your proposed system is not the WWW, and not the Semantic Web.
>> It is a different imaginary system, which you are free to develop, but you should not use the term "HTTP".
>> 
>> In the Semantic Web,  I can say
>>        <ex:i>   <fb:like>    <http://www.knox.edu/Images/_News/news_media/img/2005/obama-barack-1ss.jpg>.
>> 
>> and it unambiguously means that I like the image, not the person.
>> This is very valuable.
> 
> It would be valuable if it were true, but it is not. Firstly, using
> the same argumentation style that Jonathan employed in response
> another of Xiaoshu's emails, you have not unambiguously defined ex:i
> or fb:like and they could mean absolutely anything.

You are right, I assume that ex:i names me, as in
  @prefix ex: <http://www.w3.org/People/Berners-Lee/card>.
and I define fb:like to a  predicate that expresses that the subject
likes the object.



> 
> Secondly what resource is denoted by the knox.edu URI? I content there
> are several possibilities:
> 
> a) the person called "Barack Obama". Perhaps further RDF statements
> might say that resource is wearing a tie.

No.

> b) the photograph of that person as originally taken by the camera.
> Further RDF statements might say who the creator of that photograph
> was, or talk about the lighting used or the composition.
> 

Yes.

> c) the digital version of that photograph, perhaps scanned. Further
> RDF statements might say the digitisation process or resolution.

Well, in fact because the server could return different scans of the 
same photo under different conditions, and nothing would break,
actually (b) not (c).  Of course the web works by sending digital 
encodings, but that doesn't mean that the URI names them.

> d) the file format of that digital image. Further RDF statements might
> state the compression factor, or refer to the EXIF data that JPEGs can
> have.

RDF statements expressing something of a given set of bits
returned from the server would in many cases by in danger of being 
wrong as the server may return a different compression under different circumstances.
So RDF systems if they want to can and do stored a record of the HTTP transaction
keeping a record of the return headers and the bits.  There are various
ontologies foe this.

> I think your statement is referring to d) but its' certainly ambiguous
> in that sense. It can be disambiguated by publishing more data about
> that URI.

There are also HTTP vary:  headers which can help.
There is the ontology http://www.w3.org/2006/gen/ont
which you can use for expressing relationships between resource
which are more or less specific when it comes to various axes. 

> 
> If you think I am wrong, then please tell me what this statement means:
> 
> <ex:i>   <fb:like>    <http://128.252.39.97/SnapshotJPEG>.

It means, given fb: and ex: as above, that I like the a rather 
washed out picture of some hall, which I don't.
So it is a false statement.

(That doesn't mean I won't like a nicer picture of the same hall.
It doesn't mean I like the hall.
You can assume though that I am not going to like any
re-encoding in a different format of the same picture.).

Tim
Received on Saturday, 25 June 2011 22:42:28 GMT

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