ETAI, Reasoning about Actions and Change

Approaches to Reasoning about Actions and Change - General Issues

This discussion was originally started in the ECSTER Newsletter, and it was reproduced in the Demo issue of the ETAI News Journal for Actions and Change (May, 1997). We have now reformatted it to conform to the general structure of ETAI discussions.

The present page contains the contributions, if they are short, and the first ten or so lines of the contribution, if they are long. In the latter case, a clickable link leads to the full text of the contribution in question. This is just like how a newspaper story may start on the first page and be continued inside.


Introduction to the Debate

Current Research on Reasoning About Actions and Change

Erik Sandewall

Several approaches to reasoning about actions and change co-exist at present in the literature. The major divide seems to be between the situation calculus on one hand, and approaches using explicit time on the other hand. It may not be easy for the readers of this literature to see how the different approaches relate, and what are their respective weaknesses and strengths. Sometimes, it is even difficult for the researchers in the area to make this analysis. For example, in this recent KR paper, Ray Reiter writes: ... read the continuation here.


Initial Position Statements

Reasoning about Actions

Murray Shanahan

AI needs an action formalism that is expressive, and that incorporates a solution to the frame problem that's robust in the face of the phenomena it can represent. The formalism should be expressive enough to represent at least the following phenomena.

  1. Actions with indirect effects (ramifications)
  2. Concurrent action
  3. Non-deterministic action
  4. Narrative time
  5. Continuous change

A rigorous argument that the formalism in question solves the frame problem should be supplied.

Here comes the controversial bit. ... read the continuation here.

Comparing Action Formalisms

Rob Miller

Here are some fairly miscellaneous thoughts about comparing alternative approaches to Reasoning about Action. ...

(1) When comparing and evaluating formalisms, we need to be careful not to form too strong associations between particular methodologies (e.g. deduction and entailment methods, default reasoning techniques) and particular ontologies. I can think of a few occasions... (2) As a community, we should be encouraging work on comparing action formalisms and ontologies, and we should be critical of papers which don't contain adequate comparisons with other work (and especially with work based on different ontologies). There is now a fair body of work exploring how the Event Calculus and the Situation Calculus correspond, so there's really no excuse for lack of comparisons in this case at least. ... read the continuation here.

Approaches to Reasoning About Actions

Vladimir Lifschitz

1. Explicit time vs. the situation calculus. The following situation calculus formula seems to have no counterpart in languages with explicit time:

value(f,result(a1,s)) = value(f,result(a2,s)). (1)

It says that the value of f at the next instant of time does not depend on which of the actions a1, a2 is going to be executed. For instance,...

4. Why are there so many action languages? An action language is a formal model of the part of natural language that is used for describing the effects of actions. Whenever we improve our understanding of that part of natural language, this improved understanding may be expressed by defining a new dialect of "script-A." I expect that...

6. Explicit information about causal directions. Causality differs from material implication in that it is not contrapositive... ... read the continuation here.


The topic of this discussion was addressed again in the NRAC panel on ontologies for actions and change, which started on-line in October, 1997.