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RE: Real URLs for real things

From: Hausenblas, Michael <michael.hausenblas@joanneum.at>
Date: Wed, 21 May 2008 10:25:21 +0200
Message-ID: <768DACDC356ED04EA1F1130F97D29852016BE55C@RZJC2EX.jr1.local>
To: "Steven Pemberton" <steven.pemberton@cwi.nl>
Cc: <public-rdf-in-xhtml-tf@w3.org>


Thanks for your excellent analysis. Seems we are agreeing on most issue
but one. I'm advocating HTTP URIs and hence am not convinced that a new
scheme is needed. Can you please give me some more hints about the
characteristics of this new 'pto scheme'? For example:

+ in how far does it differ from URN (or even other schemes found at
+ is it used with HTTP?
+ who 'owns' it and who takes care of maintaining it?


[1] http://www.iana.org/assignments/uri-schemes.html

 Michael Hausenblas, MSc.
 Institute of Information Systems & Information Management
 JOANNEUM RESEARCH Forschungsgesellschaft mbH

>-----Original Message-----
>From: Steven Pemberton [mailto:steven.pemberton@cwi.nl] 
>Sent: Tuesday, May 20, 2008 10:13 PM
>To: Hausenblas, Michael
>Cc: public-rdf-in-xhtml-tf@w3.org
>Subject: Re: Real URLs for real things
>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 
>> 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 
>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 
>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."
>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 
>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 Wednesday, 21 May 2008 08:28:57 UTC

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