<s>
SIGNAL	O
is	O
a	O
programming	O
language	O
based	O
on	O
synchronized	O
data-flow	B-Application
(	O
flows	O
+	O
synchronization	O
)	O
:	O
a	O
process	O
is	O
a	O
set	O
of	O
equations	O
on	O
elementary	O
flows	O
describing	O
both	O
data	O
and	O
control	O
.	O
</s>
<s>
The	O
SIGNAL	O
formal	O
model	O
provides	O
the	O
capability	O
to	O
describe	O
systems	O
with	O
several	O
clocks	O
(	O
polychronous	O
systems	O
)	O
as	O
relational	O
specifications	B-Application
.	O
</s>
<s>
Relations	O
are	O
useful	O
as	O
partial	O
specifications	B-Application
and	O
as	O
specifications	B-Application
of	O
non-deterministic	O
devices	O
(	O
for	O
instance	O
a	O
non-deterministic	O
bus	B-General_Concept
)	O
or	O
external	O
processes	O
(	O
for	O
instance	O
an	O
unsafe	O
car	O
driver	O
)	O
.	O
</s>
<s>
Using	O
SIGNAL	O
allows	O
one	O
to	O
specify	B-Application
an	O
application	O
,	O
to	O
design	O
an	O
architecture	O
,	O
to	O
refine	O
detailed	O
components	O
down	O
to	O
RTOS	B-Operating_System
or	O
hardware	O
description	O
.	O
</s>
<s>
The	O
SIGNAL	O
model	O
supports	O
a	O
design	O
methodology	O
which	O
goes	O
from	O
specification	B-Application
to	O
implementation	O
,	O
from	O
abstraction	B-Application
to	O
concretization	O
,	O
from	O
synchrony	O
to	O
asynchrony	B-Operating_System
.	O
</s>
<s>
SIGNAL	O
has	O
been	O
mainly	O
developed	O
in	O
since	O
the	O
1980s	O
,	O
at	O
the	O
same	O
time	O
as	O
similar	O
programming	O
languages	O
,	O
Esterel	B-Language
and	O
Lustre	B-Application
.	O
</s>
<s>
The	O
SIGNAL	O
language	O
was	O
first	O
designed	O
for	O
signal	B-General_Concept
processing	I-General_Concept
applications	I-General_Concept
in	O
the	O
beginning	O
of	O
the	O
1980s	O
.	O
</s>
<s>
It	O
has	O
been	O
proposed	O
to	O
answer	O
the	O
demand	O
of	O
new	O
domain-specific	B-Language
language	I-Language
for	O
the	O
design	O
of	O
signal	B-General_Concept
processing	I-General_Concept
applications	I-General_Concept
,	O
adopting	O
a	O
dataflow	B-Application
and	O
block-diagram	B-Application
style	O
with	O
array	O
and	O
sliding	O
window	O
operators	O
.	O
</s>
<s>
A	O
full	O
compiler	B-Language
of	O
SIGNAL	O
based	O
on	O
the	O
clock	O
calculus	O
on	O
hierarchy	O
of	O
Boolean	O
clocks	O
,	O
was	O
described	O
by	O
L	O
.	O
Besnard	O
in	O
his	O
PhD	O
thesis	O
in	O
1992	O
.	O
</s>
<s>
During	O
the	O
1990s	O
,	O
the	O
application	O
domain	O
of	O
the	O
SIGNAL	O
language	O
has	O
been	O
extended	O
into	O
general	O
embedded	O
and	O
real-time	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
The	O
relation-oriented	O
specification	B-Application
style	O
enabled	O
the	O
increasing	O
construction	O
of	O
the	O
systems	O
,	O
and	O
also	O
led	O
to	O
the	O
design	O
considering	O
multi-clocked	O
systems	O
,	O
compared	O
to	O
the	O
original	O
single-clock-based	O
implementation	O
of	O
Esterel	B-Language
and	O
Lustre	B-Application
.	O
</s>
<s>
Le	O
Goff	O
,	O
the	O
abstraction	B-Application
and	O
separate	O
compilation	B-Language
formalized	O
by	O
O	O
.	O
Maffeïs	O
,	O
and	O
the	O
implementation	O
of	O
distributed	O
programs	O
developed	O
by	O
P	O
.	O
Aubry	O
.	O
</s>
<s>
The	O
Polychrony	B-Application
toolset	O
is	O
an	O
open-source	B-Application
development	I-Application
environment	O
for	O
critical/embedded	O
systems	O
based	O
on	O
SIGNAL	O
,	O
a	O
real-time	B-General_Concept
polychronous	O
data-flow	B-Application
language	O
.	O
</s>
<s>
It	O
provides	O
a	O
unified	O
model-driven	B-Language
environment	I-Language
to	O
perform	O
design	O
exploration	O
by	O
using	O
top-down	O
and	O
bottom-up	O
design	O
methodologies	O
formally	O
supported	O
by	O
design	O
model	O
transformations	O
from	O
specification	B-Application
to	O
implementation	O
and	O
from	O
synchrony	O
to	O
asynchrony	B-Operating_System
.	O
</s>
<s>
Polychrony	B-Application
is	O
a	O
set	O
of	O
tools	O
composed	O
of	O
:	O
</s>
<s>
The	O
SME	O
(	O
SIGNAL	O
Meta	O
under	O
Eclipse	B-Application
)	O
environment	O
is	O
a	O
front-end	B-Architecture
of	O
Polychrony	B-Application
in	O
the	O
Eclipse	B-Application
environment	O
based	O
on	O
Model-Driven	B-Language
Engineering	I-Language
(	O
MDE	O
)	O
technologies	O
.	O
</s>
<s>
It	O
consists	O
of	O
a	O
set	O
of	O
Eclipse	B-Application
plug-ins	O
which	O
rely	O
on	O
the	O
Eclipse	B-Language
Modeling	I-Language
Framework	I-Language
(	O
EMF	O
)	O
.	O
</s>
<s>
A	O
reflexive	O
editor	O
:	O
a	O
tree	B-Data_Structure
view	O
allowing	O
to	O
manipulate	O
models	O
conform	O
to	O
the	O
SME	O
metamodel	O
.	O
</s>
<s>
A	O
reflexive	O
editor	O
and	O
an	O
Eclipse	B-Application
view	O
to	O
create	O
compilation	B-Language
scenarios	O
.	O
</s>
<s>
A	O
direct	O
connection	O
to	O
the	O
Polychrony	B-Application
services	O
(	O
compilation	B-Language
,	O
formal	O
verification	O
,	O
etc	O
.	O
</s>
