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RE: Use/misuse of RDF:Value

From: <lagoze@cs.cornell.edu>
Date: Sun, 4 Mar 2001 16:21:48 -0500
Message-ID: <706871B20764CD449DB0E8E3D81C4D43015AA27F@opus.cs.cornell.edu>
To: dc-architecture@jiscmail.ac.uk, www-rdf-interest@w3.org
Comments inserted mid-text

> -----Original Message-----
> 
> Date: Fri, 23 Feb 2001 17:12:02 -0600
> From: Aaron Swartz <aswartz@swartzfam.com>
> To: <lagoze@cs.cornell.edu>, 
> <dc-architecture@jiscmail.ac.uk>, <www-rdf-interest@w3.org>
> Message-ID: <B6BC4A61.23652%aswartz@swartzfam.com>
> Subject: Re: Use/misuse of RDF:Value
> 
> lagoze@cs.cornell.edu <lagoze@cs.cornell.edu> wrote:
> 
> > 1. My reading of the rdf schema documentation says that Stefan's
> > suggestion to use rdfs:label for the expression of a 
> default value is
> > very conventional.  As stated in 5.2 of rdf schema, 
> rdfs:label: "This is
> > used to provide a human-readable version of a resource name".  The
> > examples throughout the document are multi-language labels for
> > definition, which seems to have nothing to do with the 
> purpose for which
> > Stephan is using it.
> 
> I don't follow -- why is this so? It seems that the usage is 
> just fine.

I'm willing to acknowledge being think, but I'm still at a complete loss
to understand this use of rdfs:label.  HOw is an "appropriate literal"
for a dc value at all related to the "human readable version of a
resource name" other than the fact that both are of type "string"?

> 
> > 3. Of special concern for the dc-architecture folks, I'm 
> still concerned
> > that the hanging of that arbitrary information off a 
> intermediate node
> > associated attached to a dc property says espresses that 
> the arbitrary
> > information is indeed a value of the dc property.
> 
> I once again refer you to the argument in:
> 
> http://jiscmail.ac.uk/cgi-bin/wa.exe?A2=ind0102&L=dc-architect
> ure&P=27229


Your argument seems to rely on the notion of a "smart system".  As
others have pointed out in the previous emails, we've been pretty
focused in DC to make sure that dumb systems are able to use a variety
of DC descriptions.  Mixing in arbitrary sub-graphs with dc properties
esstentially gives no constraints and makes it difficult for these dumb
systems.

> 
> > My reading is that Stu is suggesting a violation of
> > RDF schema which says that:
> 
> First, one cannot be in "violation" of a schema, one merely 
> has something
> which it cannot model.

Thanks for correcting my language here.

> 
> > A property can have at most one range property. It is 
> possible for it to
> > have no range, in which case the class of the property value is
> > unconstrained. 
> 
> Second, this is widely-believed to be a bug and is expected to be soon
> changed.

Do you have any notion of what that soon is.  It makes me uncomfortable
to propose a general usage that precedes the nature of a "bug fix".

> 
> > That is, I can't write a schema that says a dc property can 
> have a range
> > that is either a rdfs:literal or an intermediate node.
> 
> Third, I believe that leaving the schema unconstrained would 
> have the same
> effect since an intermediate node is a resource and the union 
> of resources
> and literals covers (to my knowledge) all possible properties in RDF.

Not comfortable with this.  The nice thing about constraints is that
they help us write programs that process the stuff.  If we formally
leave the nature of the rdf expression of dublin core, then why not
change the natural language description of all dc elements to "anything
you really want to throw in this bucket".  John Kunze, in response to
previous attempts to put complex values into dc elements commented, "ok,
then give me a rule about what can't be the value of a dc element".

> 
> > If we can't express this with an rdf schema then we are 
> left with the a
> > rather uncomfortable situation for both the dc community and the rdf
> > community, both of whom want to see a common use of technologies.
> 
> Even if this was an issue, we could simply omit this 
> constraint from the RDF
> schema. There is no need for a schema to include all 
> constraints -- even the
> schema for RDF Schema itself is missing several constraints which are
> unrepresentable!
> 
> -- 
> [ Aaron Swartz | me@aaronsw.com | http://www.aaronsw.com ]
> 
> ---------------------------------------
> Carl Lagoze, Digital Library Scientist 
> Department of Computer Science
> Cornell University
> Ithaca, NY 14853 USA
> Phone: +1-607-255-6046
> FAX: +1-607-255-4428
> email: lagoze@cs.cornell.edu
> WWW: http://www.cs.cornell.edu/lagoze/lagoze.html
> 
Received on Sunday, 4 March 2001 16:21:56 GMT

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