Graphics Programs Reference
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p
0
p
1
p
2
p
3
t
a
t
b
t
c
t
d
p
a
p
b
p
c
p
d
Figure 6.5: An example of ECS
Table 6.4: Specification of the transitions of the SPN of Fig.
6.5
transition
weight
priority
ECS
t
a
w
a
1
1
t
b
w
b
1
1
t
c
w
c
1
1
t
d
w
d
1
1
ities of firing to the same transition in different markings. Equation (
6.16)
however ensures that if we have two transitions (say transitions t
i
and t
j
),
both enabled in two different markings (say markings M
r
and M
s
), the ra-
tios between the firing probabilities of these two transitions in these two
markings remains constant and in particular equal to the ratio between the
corresponding weights assigned at the moment of the specification of the
model.
observe that in marking M
r
= (p
1
+ p
2
+ p
3
) these probabilities are:
P
{
t
a
|
M
r
}
=
w
a
(w
a
+ w
b
+ w
d
)
P
{
t
b
|
M
r
}
=
w
b
(w
a
+ w
b
+ w
d
)
P
{
t
c
|
M
r
}
= 0
and
w
d
(w
a
+ w
b
+ w
d
)
P
{
t
d
|
M
r
}
=
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