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Re: owl:sameAs use/misuse/abuse Re: homonym URIs

From: Tim Berners-Lee <timbl@w3.org>
Date: Tue, 26 Jun 2007 19:25:50 -0400
Message-Id: <CD58D10D-1709-46AD-843E-C34353E33F2C@w3.org>
Cc: "Richard Cyganiak" <richard@cyganiak.de>, "Jacek Kopecky" <jacek.kopecky@deri.org>, "Bernard Vatant" <bernard.vatant@mondeca.com>, <semantic-web@w3.org>
To: John Black <JohnBlack@kashori.com>

On 2007-06 -25, at 11:00, John Black wrote:
> [...] But surely a URI is an information resource in the same way  
> that a blog post is and so it can be represented by a web page the  
> same way a blog post is represented by the web page you get through  
> Now my FOAF URI is this http://kashori.com/JohnBlack/foaf.rdf#jpb.  
> As a URI, it is an information resource, namely a string of  
> characters conforming to rfc3986.

Well, that is not how Information Resource is used in the web  
Architecture.  An Information Resource conveys information, and in  
the web architecture it can severl representations, but any one of  
them must have a content-type (and possibly other metadata) as well  
as a string of  bits.

In other words, the architecture i snot that strings of bits are self- 
describing.  It is not that you can guess what a string of bits is  
intended to convey when you meet it on the street.  It is that the  
content-type tells you how to interpret it.  So, the same string of  
bits may signify the source markup of an HTML page when paired text/ 
plain and the document as represented in HTML (the noemal bowsers  
case) when paired with text/html.

So, strictly, you can say that an IR has a representation whcih is 48  
bytes long, but not that the IR is 45 bytes long.

> I have created a web page representation of this information  
> resource at http://kashori.com/ontology/MyURI according to standard  
> REST web architecture principles. As the owner of and therefore the  
> authority about the referent of that URI, I hereby proclaim that  
> this web URI denotes my RDF FOAF URI, http://kashori.com/JohnBlack/ 
> foaf.rdf#jpb.

In other words we would say <http://kashori.com/ontology/MyURI>  
owl:sameAs "http://kashori.com/JohnBlack/foaf.rdf#jpb".

The thing denoted by the MyURI is the string "..#jpb".

Well, yes, but is this useful?

> This uses web technologies to identify that FOAF URI by another  
> URI. In particular, as an information resource, something that can  
> be completely characterized by a message, I can identify it  
> directly with a 'slash' URI. I don't need a 303 or a 'hash' URI.

Oh, Yes you do, as a literal string is not an information resource.

> Now I can talk directly about, or mention, that FOAF URI in RDF.
> <http://kashori.com/ontology/MyURI> str:numOfCharacters 41.
> In this case, the RDF statement is about the identifier. This  
> contradicts your statement that "...RDF statements always are about  
> the referents, and never about the identifier." Here the referent  
> is the identifier.

No, not THE identifier, a different identifier.

> I am talking as directly about my FOAF URI as I am talking directly  
> about any other information resource as represented by a web page  
> by stating in RDF:
> 1. <http://kashori.com/ontology/MyURI> owl:sameAs "http:// 
> kashori.com/JohnBlack/foaf.rdf#jpb"^^xsd:anyURI.
> 2. <http://kashori.com/ontology/MyURI> dc:creator <http:// 
> kashori.com/JohnBlack/foaf.rdf#jpb>.
> In natural language, 1. that FOAF URI is the same as that literal  
> URI. and 2. that FOAF URI has a creator that is John Black.
> Finally, consider this URI: http://kashori.com/ontology/self- 
> referential. This URI identifies/denotes itself. So we can say
> <http://kashori.com/ontology/self-referential> owl:sameAs "http:// 
> kashori.com/ontology/self-referential"^^xsd:anyURI.
> Only problem is, these URI are ambiguous, we can't tell if they  
> identify the identifiers or the web pages representing the  
> identifiers.

No, they are not ambiguous, you said they represent the identifiers  
and so they must NOT return 200.

As far as I can see, the semantic web has a consistent architecture  
which works.

(I am not sure whether you are trying to understand it or to suggest  
an alternative or
try to show it doesn't work, or just check the seals. :-)


> John Black
> www.kashori.com

Received on Tuesday, 26 June 2007 23:25:52 UTC

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