Information Technology Reference
In-Depth Information
:
stain
:
up
(
lhs
)
:
up
(
rhs
)
down
(
lhs
)
down
(
rhs
)
Figure 2.9.
A bowl lled with soup is standing on a table. The soup spills out and
produces a stain if the table is lifted on one hand side but not the other. Nothing
of this sort is expected when lifting up the table on both sides simultaneously.
fluent names
up
1
,
down
1
, and
stain
0
, action name
lift-both-sides
0
, and
action law
transforms
f
down
(
lhs
)
;
down
(
rhs
)
g
lift-both-sides
into
f:
down
(
lhs
)
; :
down
(
rhs
)
g
Furthermore, let the set of state constraints consist of
8x
[
(
x
)]
up
(
lhs
)
^:
up
(
rhs
)
_
up
(
rhs
)
^:
up
(
lhs
)
stain
down
(
x
)
:
up
Influence information
I
=
f
(
up
(
x
)
;
down
(
x
))
;
(
down
(
x
)
;
up
(
x
))
;
(
up
(
x
)
;
stain
)
g
plus the constraints determine the following causal relationships:
down
(
x
) causes
:
up
(
x
)if
>
up
(
lhs
) causes
stain
if
:
up
(
rhs
)
(
x
) causes
:
(
x
)if
>
(
) causes
if
:
(
)
up
down
up
rhs
stain
up
lhs
:
down
(
x
) causes
up
(
x
)
if
>
up
(
rhs
) causes
stain
if
up
(
lhs
)
:
(
x
) causes
(
x
)if
>:
(
) causes
if
(
)
up
down
up
lhs
stain
up
rhs
(The interested reader may verify this being the output of our algorithm of
Fig. 2.6.)
Now, consider the state where the table stands rmly on the floor and
there is no stain,
S
=
f:
g
,
as depicted in Fig. 2.9. Performing
lift-both-sides
results in the prelim-
inary successor
(
)
;
(
)
; :
(
)
;
(
)
; :
up
lhs
down
lhs
up
rhs
down
rhs
stain
S
0
=
f:
up
(
lhs
)
; :
down
(
lhs
)
; :
up
(
rhs
)
; :
down
(
rhs
)
; :
stain
g
obtained through the direct eect
E
=
f:
)
g
. This pre-
liminary state violates the state constraints. The two possible instances of
(
)
; :
(
down
lhs
down
rhs
