- From: pat hayes <phayes@ai.uwf.edu>
- Date: Thu, 23 May 2002 17:32:43 -0500
- To: "R.V.Guha" <guha@guha.com>
- Cc: www-rdf-logic@w3.org
>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 -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola, FL 32501 (850)202 4440 fax phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Thursday, 23 May 2002 18:40:03 UTC