Issue 98012 | Editor: Erik Sandewall | 29.1.1998 |
Today |
Today, the ontologies discussion continues, with questions by Michael Gelfond and Luis Pereira.
Debates |
I would like to better understand the following comment by Hector Geffner:
I believe they (models of actions in AI) are all monotonic in the
set of observations. In other words, if they predict |
If I understood Hector correctly, the following may be a counter
example. Consider the following domain description D0 in the language
The language of D0 contains names for two actions,
A | ||
B | ||
true_at(P, S0). | ||
true_at(neg(F), S0). |
(Domain descriptions in
Here we are interested in queries of the type
holds(F, [A1, ...An] ) |
The entailment relation on
As expected, we have that
D0 |
occurs(B, S0). |
The second example shows how observations can change beliefs about the past. Consider a domain description D3
A | ||
F |
S0 < S1 | ||
neg(F) |
Hector, is this really a counter example or you meant something else?
Reference.
C. Baral, M. Gelfond, A. Provetti, ``Representing Actions: Laws, Observations and Hypotheses'', Journal of Logic Programming, vol. 31, Num. 1,2 and 3, pp. 201-245, 1997.
References:
j-jlp-31-201 | Chitta Baral, Michael Gelfond, and Alessandro Provetti. Representing Action: Laws, Obervations and Hypotheses. Journal of Logic Programming, vol. 31 (1997), pp. 201-244. |
Dear Erik,
I noticed in the discussion that you said:
From the point of view of diagnostic reasoning these are familiar problems, but I can't think of any work in mainstream actions and change that has addressed nonmonotonicity with respect to observations in a serious way. |
I have tackled the issue of nonmonotonicty with respect to observations. Cf my home page, the AAAI-96, ECAI-96, AIMSA-96, LPKR97, JANCL97, AI&MATH98 papers. Using a LP approach I perform abuction to explain observations. The abductive explanations may be: non-inertiality of some fluent with respect to some action; occurrence of some erstwhile unsuspected foreign concurrent action along with some action of mine; or opting for a definite initial state of the world up till then given only by a disjunction of possibilities.
You're right, the techniques I and my co-author, Renwei Li, use were first developed by me and others in the context of diagnosis using LP! In fact we haven't yet used them all up yet in actions. For a view of LP and diagnosis, as well as representing actions in LP, see our book [mb-Alferes-96].
Best, Luís
References:
mb-Alferes-96 | José Júlio Alferes and Luís Moniz Pereira. Reasoning with Logic Programs. Springer Verlag, 1996. |