W3C home > Mailing lists > Public > public-esw-thes@w3.org > March 2004

Re: Difference between dc:subject and foaf:topic

From: Dan Brickley <danbri@w3.org>
Date: Fri, 12 Mar 2004 10:48:45 -0500
To: "Miles, AJ (Alistair) " <A.J.Miles@rl.ac.uk>
Cc: "'public-esw-thes@w3.org'" <public-esw-thes@w3.org>
Message-ID: <20040312154845.GA12366@homer.w3.org>

* Miles, AJ (Alistair)  <A.J.Miles@rl.ac.uk> [2004-03-12 15:23-0000]
> 
> Can anyone tell me what's the fundamental difference between these two
> properties?

dc:subject is a relationship between a document-like-thing and some kind
of identifier for a topic/subject that the document's contents cover
(could be a Literal or a Resource, in RDF-ese).

foaf:topic is a relationship between a Document and a thing that the
document is about. It is more direct than dc:subject, and 
allows any RDF statements to be used when identifying the thing that the 
document is about.

So, for a document about me. Imagine Dewey Decimal Classification had 
a subject code for me, Dan Brickley... "ddc-000.1234567", there would be 
a dc:subject property of my homepage with that as its value (perhaps
shoe-horned into URI space somehow, eg. via a purl.org URI). By
contrast, you'd see foaf:topic used in any of several ways:

<Document rdf:about="http://rdfweb.org/people/danbri/">
  <topic>
    <Person foaf:name="Dan Brickley" foaf:aimChatID="danbri_2002"/>
  </topic>
</Document>

...is a way of saying "such and so document has as a topic a thing that 
has a foaf:name "Dan Brickley" and an aimChatID of "danbri_2002".

So foaf:topic is both direct and flexible, but does not directly use 
library-style classification schemes, thesauri etc. It is good for
referencing things that are easily identified via RDF descriptions.

dc:subject always indirects via a resource that is a subject-code (or 
similar), whereas foaf:topic directly references the thing that the 
subject-code is a code for.

Hope this makes some kind of sense!

Dan
Received on Friday, 12 March 2004 10:48:45 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:38:51 GMT