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Do resources have representations?

From: Benja Fallenstein <b.fallenstein@gmx.de>
Date: Sat, 26 Jul 2003 22:14:27 +0200
Message-ID: <3F22E123.3090408@gmx.de>
To: rdf-i <www-rdf-interest@w3.org>

Hi all,

I've noticed a thing about resources and representations that strikes me 
as peculiar.

Let's say someone puts up a Web page containing the following:

     ...seems like the <a href="http://www.w3.org/Consortium/">W3C</a>
     is composed of a million monkeys typing on typewriters, whose
     keepers occasionally publish those typescripts that look like
     a technical specification...

What does this <a> construct mean? What effect should it have in a 
browser? From <http://www.w3.org/TR/html401/struct/links.html>:

     This section introduces the link (or hyperlink, or Web link), the
     basic hypertext construct. A link is a connection from one Web
     resource to another. Although a simple concept, the link has been
     one of the primary forces driving the success of the Web.

     A link has two ends -- called anchors -- and a direction. The link
     starts at the "source" anchor and points to the "destination"
     anchor, which may be any Web resource (e.g., an image, a video clip,
     a sound bite, a program, an HTML document, an element within an HTML
     document, etc.).


     The default behavior associated with a link is the retrieval of
     another Web resource. This behavior is commonly and implicitly
     obtained by selecting the link (e.g., by clicking, through keyboard
     input, etc.).


     href = uri [CT]
         This attribute specifies the location of a Web resource, thus
         defining a link between the current element (the source anchor)
         and the destination anchor defined by this attribute.

By "retrieval of [a] resource," I presume the spec means "retrieval of a 
representation of a resource." So the link points to a resource, and if 
I click on the link, my browser is expected to show me some 
representation of this resource (it doesn't specify which representation).

Assume that http://www.w3.org/Consortium/ identifies an organization, 
the World Wide Web Consortium. Assume that I have assigned 
http://example.org/~benja/w3c to denote the same organization. Both I 
and the owners of w3.org have provided authoritative information from 
which it is clear that the two URIs identify the same resource.

We can then clearly conclude that

     <http://example.org/~benja/w3c> = <http://www.w3.org/Consortium/> .

Assume that it is true that

     <http://example.org/~benja/w3c> hasRepresentation
         "W3C -- the standards body for Web technologies." .

Then it is also true that

     <http://www.w3c.org/Consortium/> hasRepresentation
         "W3C -- the standards body for Web technologies." .

(which is not the content of the Web page behind that URI).

Given that the link in the example above, according to the HTML spec, 
points to the *resource*, does this mean that it would be acceptable for 
a browser to serve me "W3C -- the standards body for Web technologies" 
as a representation of the link target? Clearly not.

It seems to me that the current situation is,

- a URI corresponds to a set of representations
- a URI denotes a resource
- two URIs denoting the same resource can correspond to different sets 
of representations
- if I link to a URI through HTML, my intention is not only to specify 
the resource I link to, but also the set of representations that is 
shown to a user when they click on the link.

[In a sense, not the resource has a retrievable set of representations, 
but the URI that denotes the resource.]

Obviously there's something wrong with this picture, but I don't know 
how to fix it.

- Benja
Received on Saturday, 26 July 2003 16:16:11 UTC

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