Re: rdf inclusion

Jeff Heflin wrote:

>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.
>  
>
Jeff,

 Different reasoners *will* reach different conclusions, depending on 
what their inputs are. This is
just the way the real world is. People (and hence reasoners) will have 
different theories of who shot
JFK, whether Bin Laden is still alive, ... If  we architect something so 
rigid that the entire system had
to agree on one answer for each of these questions, I doubt it would be 
very interesting.

 You also make the statement that "formal semantics" (by which I assume 
you mean some kind of
tarskian model theory) will provide the answer to the problems of  
integrating data from different
sources. This is a very very strong claim that is being made explicitly 
and implictly, that is as yet
unjustified. I would really like to understand how a model theory will 
solve these problems.

 About the issue of RDF & RDFS being hard to extend --- let us be *very* 
clear on this. RDF & RDFS
were designed to be Cyc like systems [1]. They were *not* designed to be 
DL like systems. You are finding
it hard to reconcile the two. Cyc-like systems are extensible and have 
been extended, though not in a
fashion that is consistent with DL model-theories. Yes, the clothes 
don't fit the person. Maybe the problem
is with the clothes and not the person.

Guha

[1] http://www.w3.org/TR/NOTE-MCF-XML/#sec2.

Received on Thursday, 23 May 2002 14:25:01 UTC