W3C home > Mailing lists > Public > www-rdf-logic@w3.org > May 2001

metadata vs. meta-(meta)-data

From: Larry Masinter <LMM@acm.org>
Date: Mon, 21 May 2001 10:27:06 -0700
To: <www-rdf-logic@w3.org>
Message-ID: <NDBBKEBDLFENBJCGFOIJIEDDEPAA.LMM@acm.org>
I'm hoping that RDF can be modified in a way that
distinguishes between the use of RDF to make assertions
about actual web resources (data content) and its use
to make assertions about things that are described or
referenced by things on the net.

The use of "http" URIs as unique identifiers for things
that are not resources backed by HTTP web servers is
a serious confusion of levels.

The model for the sentence

 The students in course 6.001 are Amy, Tim, John, Mary, and Sue. 
 is written in RDF/XML as

<rdf:RDF>
  <rdf:Description about="http://mycollege.edu/courses/6.001">
    <s:students>
      <rdf:Bag>
	<rdf:li resource="http://mycollege.edu/students/Amy"/>
	<rdf:li resource="http://mycollege.edu/students/Tim"/>
	<rdf:li resource="http://mycollege.edu/students/John"/>
	<rdf:li resource="http://mycollege.edu/students/Mary"/>
	<rdf:li resource="http://mycollege.edu/students/Sue"/>
      </rdf:Bag>
    </s:students>
  </rdf:Description>
</rdf:RDF>

This example shows the confusion -- the description is not
about the web page at http://mycollege.edu/courses/6.001, but
it's about the course which is described by the web page at
http://mycollege.edu/courses/6.001. However, we may also want
to make assertions about the web page: when it was written,
who wrote it, when it was last updated, where it is archived,
etc.

The web page and the thing the web page is about are at
different levels of quoting, but these levels are confounded
in RDF today.

Adding a "#" at the end of the Description's about attribute's
URI doesn't really help, since it resolves into the structural
granuarity of the web page rather than into the next level of
reference.

I can think of several ways of fixing this, but they're all somewhat
unpleasant:

- leave RDF as is, add another URI scheme that means
  'the thing described by this URI'
  <rdf:description about="ttdb:http://mycollege.edu/courses/6.001">
  (ttdb - the thing described by )

- leave RDF as is, assume ttdb, and add a level of quoting if
  you want to use RDF for metadata, e.g.,
  <rdf:description about="data:text/uri,http://mycollege.edu/courses/6.001">

- Define that each relationship should be specific about its level
  of indirection, e.g., "dublin core RDF relations are about the
  URI as a web resource, but other kinds of RDF assertions might
  really about the thing described by the web resource rather than
  the web resource itself".
Received on Monday, 21 May 2001 13:30:38 GMT

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