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Re: Content negotiation: Why always redirect from non-information resource to information resource?

From: Christoph LANGE <ch.lange@jacobs-university.de>
Date: Wed, 27 Jan 2010 01:35:41 +0100
To: Georgi Kobilarov <georgi.kobilarov@gmx.de>
Cc: Linked Data community <public-lod@w3.org>, "Zholudev, Vyacheslav V." <v.zholudev@jacobs-university.de>, "Rabe, Florian" <f.rabe@jacobs-university.de>
Message-Id: <201001270135.43315.ch.lange@jacobs-university.de>
Hi Georgi,

2010-01-27 01:00 Georgi Kobilarov <georgi.kobilarov@gmx.de>:
> If a client asks the server: "please give me Berlin", the server must
> respond with "sorry, can't give you that", because Berlin is a city that
> can't be send through the wire (non-information resource), "but look over
> there, maybe that's of help". That's a 303 redirect.
> 
> The server is only allowed to respond with an HTTP 200 if it can actually
> send what the client wants.

thanks, but what if I suppose that my client is software (HTML-aware browser
or RDF-aware agent) that does not have any understanding of a city, but just
of HTTP?

I.e. if I assume that my client just finds the URI
http://not-dbpedia.org/Berlin in some RDF on the web (not caring about whether
this is an information resource or not) and dereferences it,

* case 1: requesting RDF – if the server directly serves RDF from
  http://not-dbpedia.org/Berlin, this is what the client wants
* case 2: requesting HTML – then the server would understand that the content
  (i.e. the information resource) at http://not-dbpedia.org/Berlin is not what
  the client wants, it would 303-redirect the client to, say,
  http://html.not-dbpedia.org/Berlin, which is what the client wants.

> A nice workaround are #-URIs (which I prefer...)

In our setting we are not planning to rely on "normal" #-URIs, i.e. long
documents containing lots of fragments, for various reasons.  "Cool URIs"
recommends "fake" #-URIs for non-information resources, e.g.
http://not-dbpedia.org/Berlin#this (see
http://www.w3.org/TR/cooluris/#choosing), but here I don't understand what
they are good for.

So far, I don't understand why it is recommended to have separate URIs for the
non-information resource and the (RDF/XML) information resource.  I can
understand that it might be desirable for clear communication among humans to
have two separate URIs/URLs (that's why it might be hard for me to communicate
my point), and I can also understand that from a software engineering point of
view the designer of a web server application might not want to privilege a
certain data format (e.g. RDF/XML) over the others by making the arbitrary
decision to serve that format from the URL that is also used to denote the
abstract philosophical concept.

I.e. the reasoning in
http://www.w3.org/2001/tag/doc/httpRange-14/2007-05-31/HttpRange-14#iddiv1138805816
(essentially the same as what you said above) is clear to me from a
philosophical point of view, but not from a technical one.  I'm taking a more
pragmatic view here, as the information that we would like to serve is not
necessarily "the one, true and only concept of Berlin", but rather something
more pragmatic, such as "our view of Berlin, as we happen to define it (in
RDF)" – and IMHO the latter can as well be unified with an information
resource.

Or am I entirely missing the point?

Cheers,

Christoph

-- 
Christoph Lange, Jacobs Univ. Bremen, http://kwarc.info/clange, Skype duke4701
Received on Wednesday, 27 January 2010 00:35:50 UTC

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