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RE: Which URI should be persistent when redirects are used?

From: Misha Wolf <Misha.Wolf@reuters.com>
Date: Thu, 27 Sep 2007 15:21:28 +0100
To: W3C-TAG <www-tag@w3.org>, semantic-web-ig list <semantic-web-ig.list@reuters.com>
Message-id: <A29ADE959C70A1449470AA9A212F5D80065D65E8@LONSMSXM06.emea.ime.reuters.com>

OK.  The story is ...

The IPTC is likely to approve the NewsML-G2 specification at our 
meeting in Prague in mid-October.

We use URIs to denote concepts associated with the News Object (as
values of Subject, Genre, Creator, Title, Publisher, etc).  We 
want these URIs to be invariant and to participate fully in the 
Semantic Web.  If a receiving system uses HTTP to access 
information about a concept (such as Jazz, Marcel Marceau, Mona 
Lisa, Oil, Reuters), the system hosting the taxonomy in question 
may have multiple representations of the taxonomy, eg:
-  RDF/XML
-  IPTC Knowledge Item
-  Web pages in various languages

So let's say that Mona Lisa has the following URIs:
-  the one used in News Objects
-  the one which will deliver the RDF/XML
-  the one which will deliver the Knowledge Item
-  the one which will deliver the Simplified Chinese Web page
-  the one which will deliver the Traditional Chinese Web page
-  the one which will deliver the Japanese Web page
-  the one which will deliver the International English Web page
-  the one which will deliver the US English Web page
-  etc

One could then write a set of assertions along the lines of:
-  URI-Y refers to the Simplified Chinese Web page describing URI-X

And it would be a Good Thing if URI-Y were invariant.

But (it seems to me that) it would be an even Better Thing if URI-X
were invariant.

The more invariance one demands of the hosting organisations, the
more unlikely it is that it will be delivered.

Misha

-----Original Message-----
From: Dan Connolly [mailto:connolly@w3.org] 
Sent: 27 September 2007 15:02
To: Misha Wolf
Cc: W3C-TAG; semantic-web-ig list
Subject: RE: Which URI should be persistent when redirects are used?

On Thu, 2007-09-27 at 14:47 +0100, Misha Wolf wrote:
> How about 303 redirects?

Well, reading the spec, I see "The new URI is not a substitute reference
for the originally requested resource."
http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.3.4

which strongly suggests, to me, that both URIs should be persistent.

> And what about content negotiation?

What about it?

Could you elaborate on the question? What are you trying to do?

>   The requestor's original 
> URI could be redirected to different URIs depending on MIME 
> Type and Language.
> 
> Which of these many URIs would represent the resource for the 
> SemWeb?

"the resource"? which resource? Could you tell me the beginning
of this story?


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/

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