W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > May 2008

Re: Real URLs for real things

From: Steven Pemberton <steven.pemberton@cwi.nl>
Date: Tue, 20 May 2008 22:12:58 +0200
To: "Hausenblas, Michael" <michael.hausenblas@joanneum.at>
Cc: public-rdf-in-xhtml-tf@w3.org
Message-ID: <op.ubgyfwzmsmjzpq@acer3010>

On Thu, 15 May 2008 17:30:09 +0200, Hausenblas, Michael  
<michael.hausenblas@joanneum.at> wrote:
> A lot of people had excellent thoughts on these issues, some worthwhile
> readings are:

Thanks for the list. In fact I had already read many of these, and they  
reflect exactly the problem I am complaining about.

Let's take them one by one.

> http://www.w3.org/DesignIssues/LinkedData.html


"To refer to another person in a FOAF file, the convention was to give two  
properties, one pointing to the document they are described in, and the  
other for identifying them within that document.

<#i>  foaf:knows  [
	foaf:mbox <mailto:joe@example.com>;
	rdfs:seeAlso <http://example.com/foaf/joe> ].


However, the system has the snag that it does not give URIs to people, and  
so basic links to them cannot be made.

I  recommend (e.g in weblogs on Links on the Semantic Web , Give yourself  
a URI, and and Backward and Forward links in RDF just as important) that  
those making a FOAF file give themselves a URI as well as using the FOAF  
convention.     Similarly, when you refer to a FOAF  file which gives  a  
URI to a person, use it in your reference to that person, so that clients  
which just use URIs and don't know about the FOAF convention can follow  
the link.

> http://www.w3.org/DesignIssues/HTTP-URI.html

Discusses the problem, and points to a decision, which decision is one of  
the things I am complaining about (the 303 solution). Who on earth is  
going to do that, except for people who have control over the server, and  
can be bothered?

> http://www.w3.org/DesignIssues/Abstractions.html

"A person who is interested in a web page on something is usually  
primarily interested in the thing rather than the document."

Well, exactly!

"(There are (since 2005) URIS for things which are not explicitly bound to  
a document. These require the server to respond with the name of a  
suitable document at runtime. This is more complicated)"

My point exactly!

> http://dbooth.org/2007/uri-decl/

"This paper defines these concepts and proposes some related best  
practices and a Web architectural rule specifying how URIs for  
non-information resources can be conveniently declared using existing hash  
or hashless (303-redirect) URI mechanisms."

This is a usage of the word "conveniently" that I was not previously aware  
of. ;-)

"Suppose I mint a URI to denote the moon: http://dbooth.org/2007/moon/ .   
I own the domain dbooth.org, so according to the AWWW's guidance on URI  
ownership, I have the authority to do so.  Since the moon is not an  
information resource, in conformance with the W3C TAG's httpRange-14  
decision I have configured my server such that an attempt to dereference  
that URI will result in a 303-redirect to  
http://dbooth.org/2007/moon/decl.html , which, when dereferenced, returns  
a page containing the following statements:

Statement M1: The URI "http://dbooth.org/2007/moon/" hereby names a  
particular resource, such that the following core assertions hold:
     a: http://dbooth.org/2007/moon/ is a moon.
     b: http://dbooth.org/2007/moon/ orbits the Earth.
     c: http://dbooth.org/2007/moon/ may have ancillary assertions at  
http://dbooth.org/2007/moon/about.html .

See how difficult it is? Who is going to go to all that work to reference  
the Moon except David Booth? (And maybe Michael Hausenblas :-) )

You'll see that despite how conveniently easy it is, although he mints a  
URI for the moon, he skips the step for the Earth.

But note he says "Definition: A URI declaration is a set of statements, or  
"core assertions", that authoritatively declare the association between a  
URI and a particular resource."
"A URI declaration involves a performative speech act.  (See Cowen's  
message or Wikipedia.)  Its publication by someone who has the authority  
to make the declaration -- the URI owner or delegate -- creates the  
association between a URI and a resource."

What I am suggesting is to give everyone the authority to mint URI's about  
things, not just owners of websites and domains. Those URIs then by their  
very nature create an association between the URI and a resource.

> http://www4.wiwiss.fu-berlin.de/bizer/pub/LinkedDataTutorial/

"We often end up with three URIs related to a single non-information  
1. an identifier for the resource, a2. n identifier for a related  
information resource suitable to HTML browsers (with a web page  
representation), 3. an identifier for a related information resource  
suitable to RDF browsers (with an RDF/XML representation)."

Since 2 and 3 become the same thing with RDFa (hopefully), we are left  
with 1.

"Provide for both humans and machines."


> http://internet-apps.blogspot.com/2007/11/once-more-on-information-resources-and.html

Discusses how the #me convention is not so problematic in RDFa as raw  

> http://lists.w3.org/Archives/Public/semantic-web/2007Dec/0157.html

Demonstrates convincingly the confusions that can arise from using the #me  

So in conclusion, I can say that (re-)reading these articles has only  
strengthened my feeling that we need something better than currently has  
been proposed.

So here's a problem statement: express that the author of "The Wasteland"  
is T.S. Eliot.

My proposal:

	<pto:http://www.bartleby.com/201/1.html> dc:creator  

A URI with a pto scheme allows you to follow your nose in the easiest way  
possible, because it is right in front of your nose: we are talking about  
the primary topic of the contained URI, you can follow that URI to find  
out more information. You don't need to control any server in order to  
achieve this effect, and it is minimal typing for a major use case that is  
otherwise extremely tedious to express.

(You can even pretend that dereferencing such a URI returns a 303, with a  
See Also to the contained URI if you want).

Best wishes,


> Cheers,
> 	Michael
> ----------------------------------------------------------
>  Michael Hausenblas, MSc.
>  Institute of Information Systems & Information Management
>  JOANNEUM RESEARCH Forschungsgesellschaft mbH
>  Steyrergasse 17, A-8010 Graz, AUSTRIA
> ----------------------------------------------------------
>> -----Original Message-----
>> From: public-rdf-in-xhtml-tf-request@w3.org
>> [mailto:public-rdf-in-xhtml-tf-request@w3.org] On Behalf Of
>> Steven Pemberton
>> Sent: Thursday, May 15, 2008 4:54 PM
>> To: public-rdf-in-xhtml-tf@w3.org
>> Subject: Real URLs for real things
>> Mark and I were at XTech last week. I gave my talk on "Why
>> you should have a Website"
>> (http://2008.xtech.org/public/schedule/detail/545) which
>> gives a background to why we need RDFa, and Mark gave a
>> lightning talk on RDFa.
>> But in fact RDFa seemed to be the buzzword of the conference,
>> and every other talk seemed to mention it. The most exciting
>> was Jeni Tennison's talk on adding RDFa to the London Gazette
>> (published daily since 1665).
>> http://2008.xtech.org/public/schedule/detail/528
>> Another interesting one was about a Semantic Web search
>> engine called Sindice
>> http://2008.xtech.org/public/schedule/detail/583
>> in which the speaker talked about the sort of mistakes that
>> people made when encoding semantic information. For instance,
>> somewhere there is a FOAF page that says that Tim
>> Berners-Lee's homepage is http://www.w3.org/, and somewhere
>> else that says that W3C's home page is http://www.w3.org/,
>> and so the search engine concluded that Tim and W3C are the
>> same thing.
>> Another problem that was constantly recurring, he said, was
>> due to the confusion between a page, and the thing it represented.
>> And that set me thinking. Saying stuff about something that
>> doesn't have a URL is hard, hard in RDFa, hard in RDF, and
>> usually needs blanknodes, which our grandmothers are never
>> going to understand.
>> So, does anyone feel that they have enough energy for us to
>> propose a new type of URL, the primary topic of:
>> 	pto:http://www.w3.org/ is the W3C
>> 	pto:http://www.w3.org/People/Berners-Lee is Tim BL
>> 	pto:mailto:timbl@w3.org is also Tim BL
>> 	pto:http://rdfa.info/ is RDFa
>> and so on. You would never be expected to dereference such a
>> URL, and you can see that you are talking about a meta
>> subject by inspection, and you can automatically derive:
>> 	<pto:http://www.w3.org/> foaf:isPrimaryTopicOf
>> <http:www.w3.org/>
>> It seems to me that it would be far easier to use than all
>> that "#me"
>> stuff and all those 303 replies you have to organise to do it
>> right (or is it 302?).
>> Steven
Received on Tuesday, 20 May 2008 20:13:37 UTC

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