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RE: Denotation of URIs

From: <Patrick.Stickler@nokia.com>
Date: Thu, 10 Apr 2003 09:11:37 +0300
Message-ID: <A03E60B17132A84F9B4BB5EEDE57957B01B90CA9@trebe006.europe.nokia.com>
To: <pmika@cs.vu.nl>, <pfps@research.bell-labs.com>
Cc: <zednenem@psualum.com>, <www-rdf-interest@w3.org>



> -----Original Message-----
> From: ext Peter Mika [mailto:pmika@cs.vu.nl]
> Sent: 09 April, 2003 14:40
> To: 'Peter F. Patel-Schneider'; Stickler Patrick (NMP/Tampere)
> Cc: zednenem@psualum.com; www-rdf-interest@w3.org
> Subject: RE: Denotation of URIs
> 
> 
> 
> Hi All,
> 
> While reading the discussion on the (authority over the) denotation of
> URIs, a college of mind reminded me of the long forgotten (or 
> never ever
> used) construct of rdfs:isDefinedBy.
> 
> Snippet from the spec:
> 
> "rdfs:isDefinedBy is an instance of rdf:Property that is used to
> indicate a resource defining the subject resource. This 
> property may be
> used to indicate an RDF vocabulary in which a resource is described.
> 
> A triple of the form:
> 
> S rdfs:isDefinedBy O
> 
> states that the resource O defines S. It may be possible to retrieve
> representations of O from the Web, but this is not required. When such
> representations may be retrieved, no constraints are placed on the
> format of those representations. rdfs:isDefinedBy is a subproperty of
> rdfs:seeAlso.
> 
> The rdfs:domain of rdfs:isDefinedBy is rdfs:Resource. The 
> rdfs:range of
> rdfs:isDefinedBy is rdfs:Resource."
> 
> I always marveled at the vagueness of this definition. Was this
> originally intended to mean that (in the example) the owner 
> of S has the
> authority over S? Why isn't there a uniqueness constraint then? 

A given resource can be defined by multiple schemas and other resources.
Thus, a resource may have multiple isDefinedBy statements.

E.g. one schema may define a number of properties. And other distinct schemas can
define labels and comments in particular languages. E.g.

   mySchema.rdf
   mySchema_en.rdf
   mySchema_fi.rdf
   ...

In which case, a given property may have portions of its definition specified
in numerous different schemas.

> Was
> anyone from this mailing list there when this was put in writing?
> 
> Could this definition be cleared up and given some meaning that would
> help an agent to find the "source" of a URI, i.e. the entity who
> actually knows what it was meant to denote?

Nope. It works very well for what it is intended for.

A common way to define the source and authority of RDF knowledge is to reify each
statement and specify the source(s) of the actual statement (and again, the same
statement may be made in more than one resource, so a given statement can have
more than one source) and then indirectly infer the authority of the statement
based on the ownership of the source. This is how I do it.

Of course, other folks may suggest other ways to accomplish the same result. It
would be great if there was a more standardized, agreed way to do this, to facilitate
global interoperability between systems. Perhaps in RDF 2.x ...

Patrick

--
Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, patrick.stickler@nokia.com
 
Received on Thursday, 10 April 2003 02:11:42 GMT

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