RDF Extensibility

On 07/06/2010 03:35 PM, Toby Inkster wrote:
> On Tue, 6 Jul 2010 14:03:19 +0200
> "Michael Schneider" <schneid@fzi.de> wrote:
> 
>> So, if 
>>
>>     :s "lit" :o .
>>
>> must not have a semantic meaning, what about
>>
>>     "lit" rdf:type rdf:Property .
>>
>> ? As, according to what you say above, you are willing to allow for
>> literals in subject position, this triple is fine for you
>> syntactically. But what about its meaning? Would this also be
>> officially defined to have no meaning?
> 
> It would have a meaning. It would just be a false statement. The
> same as the following is a false statement:
> 
> 	foaf:Person a rdf:Property .

Why do you think so?
I believe it is valid RDF and even valid under RDFS semantic extension.
Maybe OWL says something about disjointness of RDF properties and classes
URI can be many things.

I think there are issues about RDF extensibility which haven't been
solved and they concern:
a) semantics
b) serializations

In case of a) I don't have cleared up my thoughts yet, but generally I
would like to know:
How are semantic extensions to work together in automated system?
How to let agent know that the data is described using new RDF
extension, which the client doesn't know and the data could be (or
definitely are) false if it is interpreted using vanilla RDF semantics?

b) How should my system know that the data which is just being processed
is new revision of RDF/XML and not malformed RDF/XML when forward
compatibility was out of sight, out of mind when RDF/XML was designed?

Best,
Jiri Prochazka