<s>
Janus	B-Language
is	O
a	O
computer	O
programming	O
language	O
partially	O
described	O
by	O
K	O
.	O
Kahn	O
and	O
Vijay	O
A	O
.	O
Saraswat	O
in	O
the	O
paper	O
"	O
Actors	O
as	O
a	O
special	O
case	O
of	O
concurrent	B-Application
constraint	I-Application
(	O
logic	O
)	O
programming	O
"	O
in	O
1990	O
.	O
</s>
<s>
It	O
is	O
a	O
concurrent	B-Application
constraint	I-Application
language	O
without	O
backtracking	O
.	O
</s>
<s>
Janus	B-Language
models	O
concurrency	O
through	O
the	O
use	O
of	O
bag	O
channels	O
.	O
</s>
<s>
The	O
logic	O
of	O
the	O
bag	O
channels	O
produces	O
a	O
property	O
shared	O
by	O
the	O
actor	B-Application
model	I-Application
,	O
namely	O
that	O
the	O
order	O
of	O
arrival	O
of	O
the	O
messages	O
is	O
not	O
guaranteed	O
.	O
</s>
<s>
This	O
ability	O
to	O
pass	O
mailboxes	O
around	O
and	O
hold	O
more	O
than	O
one	O
is	O
inherited	O
in	O
computer	O
programming	O
language	O
ToonTalk	B-Language
,	O
which	O
is	O
influenced	O
by	O
Janus	B-Language
.	O
</s>
<s>
Janus	B-Language
,	O
the	O
programming	O
language	O
,	O
is	O
named	O
after	O
Janus	B-Language
,	O
the	O
two-faced	O
Roman	O
god	O
,	O
because	O
every	O
logical	O
variable	O
in	O
Janus	B-Language
has	O
as	O
its	O
two	O
"	O
faces	O
"	O
,	O
two	O
aspects	O
that	O
can	O
be	O
passed	O
as	O
arguments	O
.	O
</s>
