Jeff,

I should be more clear ...

I did not say that Cyc has a model theory. Nor did I say that it is predictable in its current form. However, I do believe that it can be made predictable, etc. with good software engineering, i.e., without a model theory. There are lots of very complex software artifacts, which have nice predictable properties which don't have a model theory. Google is nice and predictable because of good software engineering and not model theory. Somehow, your message implicitly equates model theory with nice and predictable. You have to make the case for that.

Please don't get me wrong --- I love model theory. Its a nice fun tool. I even had a whole chapter in my thesis on a model theory for contexts. But after 15 years of actually building large KBs, I am fairly unconvinced about their relevance.

BTW, for the sake of history and the many people who gave up significant portions of their lives for Cyc, the architecture of CycL, as you describe it, is documented in [1], [2], was the collaborative work of many, including David Wallace, Mark Derthick, Dexter Pratt, John Huffman and me. Keith is the implementor of the current version. It is important to be correct about these attributions.

guha

[1] Guha, R. V., D. B. Lenat, K. Pittman, D. Pratt, and M. Shepherd. "Cyc: A Midterm Report." Communications of the ACM 33 , no. 8 (August 1990).
[2] Lenat, D. B. and R. V. Guha. "Enabling Agents to Work Together." Communications of the ACM 37, no. 7 (July 1994).

Bill Andersen wrote:

On 5/23/02 13:29, "R.V.Guha" <guha@guha.com> wrote:

[to Jeff Heflin]

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.


Hi all..

It's unclear what Cyc's model theory is at all.  So if you pick some model
theory T, it's a fair bet that Cyc's model theory, whatever it is, is
inconsistent with T.  At it's base, the Cyc engine is a resolution theorem
prover augmented with special purpose modules (many of which have fixpoint
semantics) and the argumentation system for NM reasoning, so you have some
minimal model stuff thrown in.  I would defy anyone, even including Keith
Goolsbey who wrote the thing, to tell me what all of that *combined* means.
In my view, this is nothing to crow about.

Cyc is an amazing system - it does lots of incredible things.  But what is
unclear is what it doesn't do or what it gets wrong, or how long it takes to
do some given inference, etc.  All of which are undesirable properties,
IMHO, for the Semantic Web.  When I go to Google, I have some reasonable
expectation that what its crawler has seen, I will find, assuming I use the
right terms.  I would like something of the same assurance with the Semantic
Web and I wouldn't bank on a Cyc-like system giving that to me.

 .bill