Information Technology Reference
In-Depth Information
alive ( t ) ;
: fleeing ( t )
: alive ( t ) ;
: fleeing ( t )
shoot (t)
alive ( t ) ;
fleeing ( t )
: alive ( t ) ;
fleeing ( t )
: alive ( t ) ;
: fleeing ( t )
; f (2 : 16) g
shoot (t)
Figure 2.11. Shooting the turkey ( t ) always has the direct eect : alive ( t ). If
the turkey is in motion, then the action additionally causes : fleeing ( t ).
The (steady) state constraint 8x [ fleeing ( x ) alive ( x )] restricts fleeing
subjects to vivid ones. The correct information of influence in this context is
I = f (
( x ) ;
( x )) g , that is, a change of
( x ) might aect the
alive
fleeing
alive
truth-value of
( x ) but not vice versa. The constraint thus determines
a single causal relationship, viz.
fleeing
:
( x ) causes :
( x ) f >
(2.16)
alive
fleeing
Suppose action shoot ( turkey ) is performed in a state where the victim is
still alive. In case the initial state is f
) g ,
it suces to generate the direct eect, f: alive ( turkey ) g , of the corre-
sponding action law instance. If, on the other hand, the initial state is
f alive ( turkey ) ; fleeing ( turkey ) g , then the available causal relationship
needs to be applied to accommodate an additional eect: Not only does the
turkey drop dead, it also stops fleeing. The two situations are illustrated in
Fig. 2.11. We see that our state constraint may give rise to indirect eects.
In contrast, suppose we perform action startle ( turkey ) in a situation
where the turkey idles. As above, if f
(
) ; :
(
alive
turkey
fleeing
turkey
g is
the initial state, then the direct eect, fleeing ( turkey ), of the correspond-
ing action law instance suces to obtain an acceptable state. On the other
hand, consider initial state S = f: alive ( turkey ) ; : fleeing ( turkey ) g .
The only preliminary successor of S and action
alive
(
turkey
) ; :
fleeing
(
turkey
) is state
S 0 = f: alive ( turkey ) ; fleeing ( turkey ) g , obtained through the direct
eect E = f fleeing ( turkey ) g . State S 0 violates our constraint. More-
over, the only available causal relationship is not applicable here since
:
startle
(
turkey
) 62 E . Consequently, no successor state exists. In other words,
our state constraint enforces the additional precondition that the turkey must
alive
(
turkey
Search WWH ::




Custom Search