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TAG HTTP range - Issue 14

From: Tim Berners-Lee <timbl@w3.org>
Date: Thu, 3 Jul 2003 16:09:09 -0400
Cc: Public W3C <www-archive@w3.org>
To: Roy Fielding <fielding@apache.org>
Message-Id: <34FB8F54-AD92-11D7-A74A-000393914268@w3.org>

Roy,

We are tasked with making progress.  So, I am going to ask you whether 
we could move on a bit from where we got to at the end of the face to 
face at UCI. (By the way, I don't know whether I mentioned that it was 
one of the more pleasant meetings I had ever been to, especially. the 
trip to the beach and the party at your house).

So, I I'd like to work with you on this issue.  I have two routes.

Route 1.

I think we had got to the point to the point that, while you maintained 
that HTTP URIs can identify anything, you did admit that the web in 
reality depends on the expectation that if I have seen one bit of 
information with a given URI, I expect to be able to quote the URI and 
for someone else to later get back for it essentially the same 
information, for whatever local definition of "essentially".  In other 
words, if I show you a refer you to a picture of a car and you get a 
parts list that is stretching it, it probably hinders communication, 
whereas if i see a PNG and you get a JPEG we probably never even know.

So one route is to point out that because of that expectation, what is 
really invariant about the representations retrieved for the same URI 
is not that they are about the same thing, but that they convey the 
same information.  It might be a living page like "the front page of 
the LATimes" or it might be "what my car looks like".  So in the 
architecture we actually lose information unless we capture that. So, 
please, can we refer to tthe things identified by HTTP URIs as say 
"information resources" (I won't quibble over terms).   This will 
enormously help clear up the indirection bugs we get on many of the 
lists.

Route 2.

This is to say, can we please have this distinction for the semantic 
web? In other words, before, it wasn't necessary to formally 
distinguish between whether the Consortium of The Consortium's Home 
Page was identified, as people constantly resolve such things in human 
communication, and they were only used in human communication.

Now we need to build a global KR system. You say your are not into RDF, 
and that's OK, but you are quite smart enough to understand the issues 
without using it or being committed to the language.     The goal is a 
language which talks about arbitrary objects using dereferencable 
global identifiers.

Because we want to leverage the web, we obviously want to leverage URIs 
- make those identifiers URIs in some ways.  There are two ways of 
going about this.  One is to use the flexibility point in the design of 
the fragid syntax.    This says that on the web, you can make a new 
language about whatever  you like, and the fragid syntax connects (in a 
way you define) with the syntax of the new language, and the things 
identified mean whatever you like.  Example: SVG defines graphics 
things, and the frag id syntax can define a 2d window on the 2d space.  
I actually think this is a really important flexibility point in the 
design, as I would like all kinds of new languages to introduce all 
kinds of new abstract concepts in the future.

The only alternative is that we abandon the direct use of URIs for 
arbitrary things, and follow alas common view among users that a 
fragment identifier identifier identifies part of a document.  Then we 
design a language in which there is an implicit or explicit by quite 
unambiguous way of referring to "that thing described by the following 
document fragment".   Sandro has explored this in various ways.  It 
isn't very nice, IMHO.  Things like SVG's views have to go.  It doesn't 
work for RDF as an RDF file can mention an object ay many different 
places, but there is no one defining occurrence which  has a 
characteristic place in the file. So "fragment" gets a very messed up 
interpretation.

---

So, Roy.  Could we see our way to resolving this between us so we can 
then advance it in the TAG and clear the way to gettinga coordinated 
architecture with the RDF core group?

Tim
Received on Thursday, 3 July 2003 16:09:11 GMT

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