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belief states an agent may have. We assume that the agent maintains some form of
structural knowledge on actions or
know-how
within its logical beliefs which is able to
assess the reliability of achieving some desire
D
∈D
in the given situation. We denote
by
B
that the current state of beliefs
B
gives reasonable grounds to
believe that the desire
D
is reliably achievable, cf. [4]. For example, in a situation where
the agent is rich the desire “
buy a Ferrari
” is reliably achievable whereas in a situation
where the agent is poor it is not.
|
=
reliable
(
D
)
Definition 4.
Let
D
1
,...,D
n
∈D
and
μ
1
, ..., μ
n
∈
[
−
1
,
1]
. Then the set of tuples
γ
=
{
(
D
1
,μ
1
)
,...,
(
D
n
,μ
n
)
}
is called a
motivational structure
.Let
Γ
denote the set
of all motivational structures.
A motivational structure
γ
describes the motivation to follow the desires of an agent
in some specific situation. For a tuple
γ
the value
μ
is called
motivational
value
for
D
and represents the strength of the motivation. In general, a positive value
of
μ
represents a positive motivation to follow
D
while a negative value represents
motivations to not follow
D
. A zero value of
μ
describes a neutral motivation to follow
the desire
D
.
(
D, μ
)
∈
3
An Abstract Model for Motivated Agents
As in the standard
BDI
approach the inner cycle of our formal agent model starts with
incorporating newly received percepts into the belief using some belief revision func-
tion. As the world might have changed the motive state of an agent might change as
well. In order to adapt to a changed world the agent has to reconsider the current weights
and weight ranges of its motives.
Example 4.
We continue Example 3. There, the motive “
environmental awareness
” lies
in level
of Maslow's hierarchy of needs: self-actualization. The motive “
food
” lies in
the lowest level of physiological needs. If the agent is low on food and low on money
there are usually stronger grounds to prefer desires generated by motives in the lower
levels. But if the situation changes, e. g. if the agents becomes wealthy, then the weights
of the levels might change. Consider some generous level weight ranges, e. g
wr
5
(
pn
)=
[0
. As the situation has become very
reliable
and the agent
is not frightened about fulfilling its physiological needs the weights of the higher levels
decrease and therefore motives for self-actualization can become even more motivated
than motives for physiological needs.
.
4
,
1]
and
wr
(
sa
)=[0
,
0
.
6]
The adjustment of the agent's motive state is performed by some
weight adjustment
function
which determines a new level weight for the motives of the agent.
Definition 5.
Let
Δ
be a function
Δ
W
that determines for the motive state
M
in a situation described by beliefs
B
a new level weight function
Δ
:
Ω
×B→
(
M, B
)
.
After adjusting the motive state of the agent with a new level function the motivational
structure might be subject to change as well.
