- From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
- Date: Fri, 31 Jan 2003 09:45:59 -0500 (EST)
- To: bwm@hplb.hpl.hp.com
- Cc: www-rdf-comments@w3.org
From: Brian McBride <bwm@hplb.hpl.hp.com> Subject: Re: Can RDF say anything about anything? Date: Fri, 31 Jan 2003 06:51:29 +0000 > At 09:48 30/01/2003 -0500, Peter F. Patel-Schneider wrote: > > >Can RDF say anything about anything? > > > >The RDF documents are contradictory on this point. The Primer indicates > >that RDF can be used to let anyone ``say anything they want about existing > >resources'' with no exception for the resources used by RDF. [Section > > 3.2] Concepts says > >that ``RDF is an open-world framework that allows anyone to make simple > >assertions about anything''. [Section 2.2.6, and elsewhere] > > However, Concepts also says that ``Certain > >URIs are reserved for use by RDF, and may not be used for any purpose not > >sanctioned the RDF specifications.'' [Section 3.7] > > > >What is the situation here? > > Peter, > > As this comment affects several documents, I'll respond. > > As a general point, it is helpful if you can provide links to the sections > of documents where you have a problem with the text, or at the least > section numbers. Isn't that what the Search/Find capabilities of browsers are for? I would expect that an interested reader would want to know where else Concepts talks about being able to say anything about anything. I've added section numbers to my comment above. > Specifically about this point, I don't yet see the contradiction to which > you refer. Can you offer a test case to illustrate this contradiction. Well, if I believed the ``say anything about anything'' wording, I should really be able to say anything about, for example, rdf:ID, perhaps even saying that it is a class with an instance, as in ... <rdf:ID rdf:about="#IDinstance"> <rdfs:comment>An instance of rdf:ID.</rdfs:comment> </rdf:ID> ... A better example, perhaps, would be using RDF to critique RDF, as in ... <rdfs:Class rdf:about="#broken"> <rdfs:comment>The class of broken features in RDF.</rdfs:comment> </rdfs:Class> <broken rdf:about="http://www.w3.org/1999/02/22-rdf-syntax-ns#ID"> <rdfs:comment>rdf:ID is broken because it can only occur once in an rdf document.</rdfs:comment> </broken> <broken rdf:about="http://www.w3.org/2000/01/rdf-schema#comment"> <rdfs:comment>rdfs:comment is broken because it brings in social meaning.</rdfs:comment> </broken> ... A third example, would be to use one of the RDF URIs as a property, as in: ... <rdf:Property rdf:about="http://www.w3.org/1999/02/22-rdf-syntax-ns#ID"> <http://www.w3.org/1999/02/22-rdf-syntax-ns#ID rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#ID"/> </rdf:Property> ... Are these three examples legal in RDF? The first two quotes I presented above would indicate so. The first example, however, is illegal according to RDF Syntax. The second example is, I think, *legal* but this goes counter to the third quote I presented above. The third example is illegal according to RDF Syntax, and I don't think that there is any way of generating this triple in RDF/XML. > Brian It would be interesting to determine just which sets of triples whose first element is a URI reference or a blank node; whose second element is a URI reference; and whose third element is a URI reference, a literal, or a blank node cannot be generated from RDF/XML. (I have deliberately not called this set the set of RDF graphs.) I have already mentioned that I believe that there are some that cannot be so generated. peter PS: On a related note, is rdfs:Class rdfs:Class rdfs:Class . allowed? Section 3.7 of Concepts would indicate not, as it uses rdfs:Class for a ``purpose not sanctioned [by] the RDF specification''. This normative caution needs *much* more care in its formulation.
Received on Friday, 31 January 2003 09:47:35 UTC