Information Technology Reference
In-Depth Information
:
up
(
s
1
)
:
up
(
s
2
)
:
light
:
broken
:
wiring-problem
:
malfunc
1
:
malfunc
2
Figure 4.1.
In this electric circuit, a light bulb is involved in two otherwise in-
dependent sub-circuits. The one on the right hand side includes a battery which
is supposed to be so powerful|under normal circumstances|that it destroys the
bulb as soon as switch
s
2
gets closed. Normally, the two batteries, the wiring, and
the light bulb are in order.
It is straightforward to verify that this result is transferable to the gener-
alizations of the algorithm of Fig. 2.6 developed in the section on influence
information (Section 2.5).
It is clear that the purpose of introducing a notion of abnormality into
state constraints is to assume normal circumstances by default. In the con-
text of the Qualication Problem it proved vital, to this end, to account for
the fact that abnormalities may be caused by the performance of actions.
It should not come as a surprise if something similar is observed in case of
qualied ramications, and indeed the following scenario shows how excep-
tions to state constraints can wilfully be brought about. Global minimization
of abnormalities is therefore inappropriate as regards state constraints and
indirect eects, too.
Example 4.2.1.
Suppose the light bulb is involved in a second, otherwise in-
dependent sub-circuit consisting of its own battery and switch, see Fig. 4.1.
Suppose further that the new battery, without an intermediate resistor, is too
powerful for our light bulb so that the latter gets broken as soon as current
flows through the rightmost sub-circuit.
As a model of this circuit, let
D
be the ramication domain consisting of
entities
wiring-problem
0
,
malfunc
1
0
,
malfunc
2
0
,
ab
1
0
, and
ab
2
0
; and action name
toggle
0
up
1
,
light
0
,
broken
0
,
s
1
and
s
2
; fluent names
along
with the action laws
(
x
)
transforms
f
(
x
)
g
into
f:
(
x
)
g
toggle
up
up
toggle
(
x
)
transforms
f:
up
(
x
)
g
into
f
up
(
x
)
g
The set of state constraints shall divide into two non-steady, namely,
