********************************************************************
    ELECTRONIC NEWSLETTER ON  REASONING ABOUT ACTIONS AND CHANGE        
Issue 98019             Editor: Erik Sandewall             21.2.1998
Back issues available at http://www.ida.liu.se/ext/etai/actions/njl/
********************************************************************



                    *********  TODAY  *********

Today, additional discussion on Peter Grunwald's article at the
Commonsense workshop.



                 *********  DISCUSSIONS  *********

             ---  ARTICLES AT COMMONSENSE WORKSHOP  ---

        ========================================================
        |  AUTHOR: Peter Grunwald
        |  TITLE:  Ramifications and sufficient causes
        ========================================================

--------------------------------------------------------
|  FROM: Erik Sandewall
--------------------------------------------------------

Peter,

You wrote

> ... I am very explicit in my article about the `physics' of Do: 
> I state precisely what has to happen in a domain in order for $Do(X,B)$ 
> to be the case in that domain; no such statement about $Caused$ can be 
> found in Lin's work. 
> 
> Namely, $Do(X,B)$ means that an intervention takes place that sets the
> value of $X$ to $B$. ...
> 
> Lin's use of the predicate $caused$ has not such a clear interpretation.

But Lin (1995) wrote:

> The ternary predicate $Caused$ - for any fluent $p$, any truth value $v$,
> and any situation $s$, $Caused(p,v,s)$ is true if the fluent $p$ is
> caused (by something unspecified) to have the truth value $v$ in the
> situation $s$.

What is the difference?

Erik

--------------------------------------------------------
|  FROM: Camilla Schwind
--------------------------------------------------------

As far as I have understood your approach, you do not use a causality
predicate (or connective), but rather you define a causality
relationship or causal implication by means of material implication as 
"Do(p,b) -> Do(q, b')" or "a -> Do(p,b)"
as in example 3 (6) "Do(Alive(t),false) -> Do(Walking(t), false)"
and (3) Shoot -> Do(Alive(1), FALSE)

But then you can derive classically, "A & Do(p,b) -> Do(q, b')", for any
formula A. In other words, your causality relation appears to be
MONOTONIC. I think however  that  causal implication should be
NON-MONOTONIC. For example, from you axiom (3), you can derive   
"Shoot & not-loaded -> Do(Alive(1),False)"

Does you approach behave in this way and do you think that causality
should rather be non-monotonic?

--------------------------------------------------------
|  FROM: Vladimir Lifschitz
--------------------------------------------------------

Hi Erik,

> You mentioned in your talk that Lin's use of the mnemonic "causes" tends
> to be misleading. I agree with this, and indeed the observation from our 
> group to his work was that it was more or less a reformulation of what 
> had already been done using occlusion. 

Can you please explain this?

Regards,
Vladimir

********************************************************************
 This Newsletter is issued whenever there is new news, and is sent
 by automatic E-mail and without charge to a list of subscribers. 
 To obtain or change a subscription, please send mail to the editor,
 erisa@ida.liu.se. Contributions are welcomed to the same address.
 Instructions for contributors and other additional information is
 found at:   http://www.ida.liu.se/ext/etai/actions/njl/
********************************************************************