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RE: working around the identity crisis

From: <Patrick.Stickler@nokia.com>
Date: Tue, 23 Nov 2004 11:43:18 +0200
Message-ID: <1E4A0AC134884349A21955574A90A7A50ADDBC@trebe051.ntc.nokia.com>
To: <dirkx@webweaving.org>, <stefano@apache.org>
Cc: <jeen@aduna.biz>, <A.J.Miles@rl.ac.uk>, <www-rdf-interest@w3.org>, <public-esw-thes@w3.org>



> -----Original Message-----
> From: www-rdf-interest-request@w3.org
> [mailto:www-rdf-interest-request@w3.org]On Behalf Of ext 
> Dirk-Willem van
> Gulik
> Sent: 23 November, 2004 00:46
> To: Stefano Mazzocchi
> Cc: Jeen Broekstra; Stickler Patrick (Nokia-TP-MSW/Tampere);
> A.J.Miles@rl.ac.uk; www-rdf-interest@w3.org; public-esw-thes@w3.org
> Subject: Re: working around the identity crisis
> 
> 
> 
> 
> 
> On Thu, 18 Nov 2004, Stefano Mazzocchi wrote:
> 
> > There is a difference.
> >
> > Dereferencing http://blah.com/foo#bar will send "foo" to 
> the server, and
> > keep "bar" on the client.
> >
> > Dereferencing http://blah.com/foo/bar will send both "foo" 
> and "bar" to
> > the server.

Quite true.

> ..
> > I personally think that once Sparql web services are 
> available, the #
> > vs. / debate will very likely disappear, because at that 
> point, you can
> > dereference a single URI, even if it uses a #

Really? 

How does SPARQL provide access to an actual representation? E.g.
a JPEG, a PDF, an HTML web page? It might provide some RDF which
indicates where one might access a representation, but SPARQL is
not a URIref resolution solution. It does not replace HTTP or similar
protocols.

Are you suggesting that web clients, in order to access representations
of resources, must collaborate with one or more *centralized* knowledge
bases to obtain information that will allow them to locate/access
representations? I hope not. That would be a huge leap backwards.

--

In any case, if we're talking about discovering knowledge about
a resource, how would a client benefit from SPARQL if all it has
is the URI and no additional knowledge?

Here is a URI: http://example.org/78fa28b3-aab7-4551-b9b0-99e28fa87ecf#x891

You have no other knowledge relating to the secondary resource
identified by that URI, or the primary resource identified by the
base URI, or the host 'example.org'.

How does SPARQL help?

OK, so perhaps you are aware of a few SPARQL enabled knowledge 
services, or you are able to somehow discover such services.

Let's say that one or more of them actually know something about
the resource in question. Well, how can you be sure that knowledge
is authoritative? How do you know that the owners/managers of 
example.com will agree with what is being asserted by those third
party services?

And how much effort does your web client have to expend to locate
and query those service and determine if the knowledge it provides is
authoritative?

If all you have is the URI and you want an authoritative description of 
the resource, there is a better way.

With URIQA [1], you can do it with one request, even if you have
a URIref with a fragid:

MGET 78fa28b3-aab7-4551-b9b0-99e28fa87ecf
Host: example.org
URIQA-uri: http://example.org/78fa28b3-aab7-4551-b9b0-99e28fa87ecf#x891

(the header 'URIQA-uri:' specifically addresses the problem of
fragids not being reliably conveyed to servers in the request URI)

Now, the above URIQA request allows you to obtain an authoritative 
description of the resource in question, directly from the web 
authority (presuming the web authority is 'URIQA enlighted').

Of course, URIQA doesn't solve the inefficiency of obtaining a 
(kind of) representation of a secondary resource using just GET.

Using URIs without fragids solves that problem.

--

Before anyone jumps on me for supposedly "dissing" SPARQL, let
me state that I think SPARQL is *great*, and I eagerly await a 
broad deployment of services supporting it. But there is a huge
difference between a general query solution, which is inherently
centralized, and globally ubiquitous, decentralized mechanisms for 
either (a) accessing representations of resources directly from a web
authority of the identifying URI, or (b) bootstrapping the knowledge 
of an agent with authoritative knowledge from web authorities -- when
in both cases all the agent has is the URI.

SPARQL will provide a tremendous amount of utility, but it does
not directly impact the httpRange-14 debate nor provide a solution
for resolving URIrefs with fragids to representations.

> Note that any DDDS lookup also includes the '#' - and hence 
> allows you to
> sidestep this issue if needed.

True. Though, unfortunately, I don't see DDDS ever taking off
given the magnitude of the management hurdles that would be
necessary to see global, ubiquitous deployment, such that it
would provide the breadth and efficiency of access to representations
presently provided by HTTP. I won't be disappointed if I'm 
proven wrong, as I think DDDS has alot of very nice features,
but I'll be surprised if it ever really takes root on a global
scale.

Regards,

Patrick
Received on Tuesday, 23 November 2004 09:44:53 GMT

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