<s>
The	O
behavior	O
of	O
a	O
given	O
DEVS	B-Application
model	O
is	O
a	O
set	O
of	O
sequences	O
of	O
timed	O
events	O
including	O
null	O
events	O
,	O
called	O
event	B-Application
segments	I-Application
,	O
which	O
make	O
the	O
model	O
move	O
from	O
one	O
state	O
to	O
another	O
within	O
a	O
set	O
of	O
legal	O
states	O
.	O
</s>
<s>
In	O
addition	O
,	O
since	O
the	O
behavior	O
of	O
a	O
given	O
DEVS	B-Application
model	O
needs	O
to	O
define	O
how	O
the	O
state	O
transition	O
change	O
both	O
when	O
time	O
is	O
passed	O
by	O
and	O
when	O
an	O
event	O
occurs	O
,	O
it	O
has	O
been	O
described	O
by	O
a	O
much	O
general	O
formalism	O
,	O
called	O
general	O
system	O
 [ ZPK00 ] 	O
.	O
</s>
<s>
In	O
this	O
article	O
,	O
we	O
use	O
a	O
sub-class	O
of	O
General	O
System	O
formalism	O
,	O
called	O
timed	B-Application
event	I-Application
system	I-Application
instead	O
.	O
</s>
<s>
Depending	O
on	O
how	O
the	O
total	O
state	O
and	O
the	O
external	O
state	O
transition	O
function	O
of	O
a	O
DEVS	B-Application
model	O
are	O
defined	O
,	O
there	O
are	O
two	O
ways	O
to	O
define	O
the	O
behavior	O
of	O
a	O
DEVS	B-Application
model	O
using	O
Timed	B-Application
Event	I-Application
System	I-Application
.	O
</s>
<s>
Since	O
the	O
behavior	B-Application
of	I-Application
a	I-Application
coupled	I-Application
DEVS	I-Application
model	O
is	O
defined	O
as	O
an	O
atomic	O
DEVS	B-Application
model	O
,	O
the	O
behavior	B-Application
of	I-Application
coupled	I-Application
DEVS	I-Application
class	O
is	O
also	O
defined	O
by	O
timed	B-Application
event	I-Application
system	I-Application
.	O
</s>
<s>
Suppose	O
that	O
a	O
DEVS	B-Application
model	O
,	O
</s>
<s>
Then	O
the	O
DEVS	B-Application
model	O
,	O
</s>
<s>
For	O
a	O
total	O
state	O
at	O
time	O
and	O
an	O
event	B-Application
segment	I-Application
as	O
follows	O
.	O
</s>
<s>
If	O
unit	O
event	B-Application
segment	I-Application
is	O
the	O
null	O
event	B-Application
segment	I-Application
,	O
i.e.	O
</s>
<s>
If	O
unit	O
event	B-Application
segment	I-Application
is	O
a	O
timed	O
event	O
where	O
the	O
event	O
is	O
an	O
input	O
event	O
,	O
</s>
<s>
If	O
unit	O
event	B-Application
segment	I-Application
is	O
a	O
timed	O
event	O
where	O
the	O
event	O
is	O
an	O
output	O
event	O
or	O
the	O
unobservable	O
event	O
,	O
</s>
<s>
Computer	O
algorithms	O
to	O
simulate	O
this	O
view	O
of	O
behavior	O
are	O
available	O
at	O
Simulation	B-Algorithm
Algorithms	I-Algorithm
for	I-Algorithm
Atomic	I-Algorithm
DEVS	I-Algorithm
.	O
</s>
<s>
Suppose	O
that	O
a	O
DEVS	B-Application
model	O
,	O
</s>
<s>
For	O
a	O
total	O
state	O
at	O
time	O
and	O
an	O
event	B-Application
segment	I-Application
as	O
follows	O
.	O
</s>
<s>
If	O
unit	O
event	B-Application
segment	I-Application
is	O
the	O
null	O
event	B-Application
segment	I-Application
,	O
i.e.	O
</s>
<s>
If	O
unit	O
event	B-Application
segment	I-Application
is	O
a	O
timed	O
event	O
where	O
the	O
event	O
is	O
an	O
input	O
event	O
,	O
</s>
<s>
If	O
unit	O
event	B-Application
segment	I-Application
is	O
a	O
timed	O
event	O
where	O
the	O
event	O
is	O
an	O
output	O
event	O
or	O
the	O
unobservable	O
event	O
,	O
</s>
<s>
Computer	O
algorithms	O
to	O
simulate	O
this	O
view	O
of	O
behavior	O
are	O
available	O
at	O
Simulation	B-Algorithm
Algorithms	I-Algorithm
for	I-Algorithm
Atomic	I-Algorithm
DEVS	I-Algorithm
.	O
</s>
<s>
Since	O
the	O
number	O
of	O
possible	O
values	O
of	O
is	O
the	O
same	O
as	O
the	O
number	O
of	O
possible	O
input	O
events	O
coming	O
to	O
the	O
DEVS	B-Application
model	O
,	O
that	O
is	O
unlimited	O
.	O
</s>
<s>
If	O
we	O
do	O
n't	O
care	O
the	O
finite-vertex	O
reachability	O
graph	O
of	O
a	O
DEVS	B-Application
model	O
,	O
View1	O
has	O
an	O
advantage	O
of	O
simplicity	O
for	O
treating	O
the	O
elapsed	O
time	O
every	O
time	O
any	O
input	O
event	O
arrives	O
into	O
the	O
DEVS	B-Application
model	O
.	O
</s>
<s>
But	O
disadvantage	O
might	O
be	O
modelers	O
of	O
DEVS	B-Application
should	O
know	O
how	O
to	O
manage	O
as	O
above	O
,	O
which	O
is	O
not	O
explicitly	O
explained	O
in	O
itself	O
but	O
in	O
.	O
</s>
<s>
When	O
a	O
DEVS	B-Application
model	O
receives	O
an	O
input	O
event	O
,	O
View2	O
resets	O
the	O
elapsed	O
time	O
by	O
zero	O
only	O
if	O
.	O
</s>
<s>
If	O
the	O
DEVS	B-Application
model	O
needs	O
to	O
ignore	O
in	O
terms	O
of	O
the	O
lifespan	O
control	O
,	O
modellers	O
can	O
use	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
we	O
can	O
abstract	O
behavior	O
of	O
such	O
a	O
DEVS-class	O
network	O
,	O
for	O
example	O
SP-DEVS	B-Application
and	O
FD-DEVS	B-Application
,	O
as	O
a	O
finite-vertex	O
graph	O
,	O
called	O
reachability	O
graph	O
 [ HZ06 ]  [ HZ07 ] 	O
.	O
</s>
