Re: rdf inclusion

Tim,

I've responsed to a couple of your points below. I hope you don't mind
that I've snipped a lot of the original message.

Jeff

Tim Berners-Lee wrote:
> 
<snip>
>
> When you use a term (eg Property) in a namespace, its meaning is defined
> by the definer of that namespace.  You are (unlike in english)
> bound to use a term according to its creator's definition.
>

But how do you know what the creator's definition is? In RDF it is
possible to have assertions about the same URI scattered across millions
of documents. How can you determine which ones agree with the creator's
definition, and which ones don't? Surely, you wouldn't suggest that you
ignore everything that's not in the namespace document for that URI?
That would severely restrict extensibility. It would mean, among other
things, that you couldn't subclass or superclass something defined in
another namespace, and as a result, all namespaces would become
unrelated islands.

<snip> 

> > This is exactly why RDF as-is is not appropriate for the Semantic Web.
> > It really wasn't designed for the problems of a distributed,
> > heterogeneous information environment.
> 
> That actually isn't true.  It was specifically designed for such an
> environment.

I believe that it was intended for such an environment, but IMHO it
falls well short of those goals. In order to handle a distributed
environment, you need more than just "all identifiers will be URIs." You
need some way to come up with shared definitions even though global
agreement is impossible. To make this machine processable, you need a
formal semantics that explicitly takes into account how the distributed
axioms used to reason about a set of documents is assembled. Otherwise,
different reasoners can conclude wildly different things from the exact
same information, providing us absolutely no guarantees about
interoperibility. Now I understand that RDF was designed to be a
foundation which a lot of things could be eventually built on (I've seen
the "layer cake" diagram a million times). However, I think that the
distributed nature of the Semantic Web should be a fundamental issue,
and not just an "add-on." Furthermore, now that people are beginning to
build some of these upper layers, they are finding that RDF is not as
easy to extend as they might have wished: the WebOnt WG is already
discovering that extending RDF with additional semantics is not a
trivial matter.

Received on Thursday, 23 May 2002 10:49:41 UTC