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from 0 to 1. With the idea of a relative autonomy of sustainability above, this parameter
reflects the stability and activity of the module, i.e., as AL increases the functioning of the
module becomes more stable.
A fundamental characteristic of modules is that they interact with each other. The functional
proximity between two elements is calculated as follows. First, the following characteristic
for module i (and j, accordingly) at iteration m is computed
kn
,
k
k
IV
CV
im
im
,
1
k
1
me
(1)
im
,
n
afterward another parameter is calculated
kn
k
k
2
IV
CV
me
)
im
,
im
,
1
im
,
k
1
sd
(2)
im
,
n
and then the functional proximity between i and j, fp(i,j) is
sd
sd
jm
,
im
,
fp i j
(, )
|
|
(3)
m
AL
*
me
AL
*
me
im
,
1
im
.
j m
,
1
j m
,
The interaction between module i and module j
at iteration m occurs if fp(i,m) is less than a
threshold (p1) plus a small noise. The fact that modules interacts only if its functional
proximity is less than a threshold is an implementation of the idea of minimal construction
costs. The result of the interaction between module i and module j
is as follows:
k
k
k
(
CV
(
CV
IV
) * (1
AL
)) *
p
2
im
,
1
jm
,
1
jm
,
im
,
1
k
k
CV
CV
(4)
im
,
im
,
1
z
k
k
k
(
CV
(
CV
IV
) * (1
AL
)) *
p
2
jm
,
1
im
,
1
im
,
jm
,
1
k
k
CV
CV
(5)
jm
,
jm
,
1
z
It is suggested that modules interact in parallel and the formulae reflect this. Owing to
interactions, the activation level of each module (for example, module i at iteration m) is also
changed :
t
*4*(1
p
L
)
im
,
im
,
1
AL
p
3*
AL
(6)
im
,
im
,
1
z
where both p3 and p4 <1 and t
i,m
is the number of interactions between module i
and the
other modules of the system at iteration m.
It is easy to see that as the AL of a module increases, the components of the module become
less prone to change. In addition, if a module did not interact with other modules at the last