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.

But Jeff's point is that different reasoners will come up with 
different conclusions from the *same* inputs. Of course there will be 
rival thoeries on the web, though everyone seems to assume that this 
will somehow not be a problem for the SW (I think it is a huge 
problem.) BUt Jeff is making a nastier point: the same content as 
input might produce very different conclusions as output.

>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.

What does that mean? CYCL is a notational variety of FOL, right? In 
what way is that 'extensible' ? It doesn't enable one to extend the 
model theory.

Pat



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Received on Thursday, 23 May 2002 18:40:03 UTC