[from Avery Andrews (920902.0914)]
(Thomas Baines 92090909)
> I think Avery almost has it.
Spurred on by this, I'll dump the rest of this file. Before Penni
introduced me to Interactive AI, but after I started getting CSGNet,
it struck me that there was something very wierd about the discussions
of the `frame problem' in my AI books, because they seemed to be
concerned with the problems faced by programs that attempted to imagine
everything that might happen in some domain that they had no practical
experience in.
By contrast, real planning, as carried out with some modicum of success
by real people (we have 4 people, 1 car, 7 hard commitments & 3 wishes --
how are we going to get thru Saturday?) is carried out in domains where
people have a lot of practical experience. Consider a typical operator
(= step in a plan). In addition to its desired effect, it will have
various side-effects, which can be grouped into three types:
a) irrelevant (when I execute DRIVE(OWEN,BELCONNEN), the place on the
driveway where the car is normally parked will get wet if it
rains).
b) relevant, but routinely controllable (as a result of the driving, the
fuel-level of the car will decrease). One of the effects of culture
is to increase the routine controllability of side effects.
c) relevant, but uncontrollable. (while I am doing the driving, there
won't be any car at home, so no other person can do any driving).
So the real-world planner can find out from hearsay and experience what the
type (c) consequences of his/her actions are, and construct `clean' sets of
operators that have few such consequences. The general intractability of
planning means that real plans have to be quite short, so that experienced
and competent people would have large libraries of operators, which might
be individual quite complicated (like the tricks that people make up to do
the last layer of the Rubik's cube).
In terms of everyday live, it strikes me that errors are very often made
when a side-effect of an operator switches from type a) to type c).
E.g., when a family with two drivers is reduced from having two cars to
only one, they are constantly making plans which presuppose that another
car will be available when one has been driven off somewhere. It took
My wife and I a tremendously long time to stop making up these kinds of
errors after we had the use of a friend's car for six months (tho we did
usually manage to spot our mistake before anyone actually drive off to
somewhere).
And, as Penni has been saying to me recently, a lot of the info about
useful operations doesn't have to be figured out at all - you can pick it
up by watching and listening, because it's just floating around in the
culture.
Avery.Andrews@anu.edu.au