– “fact of strength m”, “obligation of strength m”, “forbiddance of strength m”
and “permission of strength m” are represented by extended vector annotations
[(m, 0), α], [(m, 0), β], [(0, m), β] and [(0, m), γ], respectively, where m is a posi-
tive integer.
Therefore, for example, a weva-literal p : [(2, 0), α] can be intuitively interpreted as “it
is known that the literal p is a fact of strength 2”, and a weva-literal q : [(0, 1), β] can be
intuitively interpreted as “the literal q is forbidden of strength 1”.
3 Defeasible Deontic Drivers’ Model
Suppose that a man is driving a car. Then, how does the car driver decide the next action
for controlling car speed such as braking or acceleration ? It is easily supposed that, for
example, if the traffic light in front of the car is red, the driver has to slow down the
car, or if there is enough distance from the driver’s car to the precedent car, the driver
may speed up the car. If we model such drivers’ car speed control, we should consider
conflicting informations such as “traffic light is red” and “enough distance to speed up”,
and its conflict resolving. It also should be considered that car drivers reason car speed
control based on not only detected physical information such as the current car speed
but also traffic rules such as “keep driving at less than speed limit”. For example, if a
driver is driving a car over the speed limit of the road, the driver would slow down the
car even if there is no car ahead of the car, then, it is supposed that there exists strong
forbiddance from driving over the speed limit, and eventually it may turn into obligation
to slow down the car. On the other hand, if a driver is driving a car at very slow speed,
the driver would speed up the car even if the traffic light far ahead of the car is red, then,
it is also supposed that there exist both strong permission and weak forbiddance to
speed up the car, then only the permission is obtained by defeasible deontic reasoning,
and eventually it may turn into obligation to speed up the car. Therefore, we can easily
model such drivers’ decision making for car speed control by EVALPSN defeasible
deontic reasoning as described in the above example. In this section, we introduce the
EVALPSN drivers’ model that can derive the three car speed control actions, “slow
down”, “speed up”, or “keep the current speed” in EVALPSN programming. We define
the drivers’ model in the following subsections.
3.1 Framework for EVALPSN Drivers’ Model
1. Forbiddance or permission for the car speed control action, “speed up” are derived
based on the traffic rules,
– it is obligatory to obey traffic signal,
– it is obligatory to keep the speed limit, etc.,
and the following detected information,
– the object car speed,
– the precedent car speed,
– the distance between the precedent and objective cars,
– the distance to the intersection or the curve ahead of the objective car ;
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