<s>
In	O
type	O
theory	O
,	O
session	B-Operating_System
types	I-Operating_System
are	O
used	O
to	O
ensure	O
correctness	O
in	O
concurrent	B-Operating_System
programs	O
.	O
</s>
<s>
They	O
guarantee	O
that	O
messages	O
sent	O
and	O
received	O
between	O
concurrent	B-Operating_System
programs	O
are	O
in	O
the	O
expected	O
order	O
and	O
of	O
the	O
expected	O
type	O
.	O
</s>
<s>
Session	B-Operating_System
type	I-Operating_System
systems	O
have	O
been	O
adapted	O
for	O
both	O
channel	B-Operating_System
and	O
actor	B-Application
systems	I-Application
.	O
</s>
<s>
Session	B-Operating_System
types	I-Operating_System
are	O
used	O
to	O
ensure	O
desirable	O
properties	O
in	O
concurrent	B-Operating_System
and	O
distributed	B-Architecture
systems	I-Architecture
,	O
i.e.	O
</s>
<s>
Interaction	O
between	O
two	O
processes	O
can	O
be	O
checked	O
using	O
binary	O
session	B-Operating_System
types	I-Operating_System
,	O
while	O
interactions	O
between	O
more	O
than	O
two	O
processes	O
can	O
be	O
checked	O
using	O
multiparty	O
session	B-Operating_System
types	I-Operating_System
.	O
</s>
<s>
In	O
multiparty	O
session	B-Operating_System
types	I-Operating_System
interactions	O
between	O
all	O
participants	O
are	O
described	O
using	O
a	O
global	O
type	O
,	O
which	O
is	O
then	O
projected	O
into	O
local	O
types	O
that	O
describe	O
communication	O
from	O
the	O
local	O
view	O
of	O
each	O
participant	O
.	O
</s>
<s>
Importantly	O
,	O
the	O
global	O
type	O
encodes	O
the	O
sequencing	O
information	O
of	O
the	O
communication	O
,	O
which	O
would	O
be	O
lost	O
if	O
we	O
were	O
to	O
use	O
binary	O
session	B-Operating_System
types	I-Operating_System
to	O
encode	O
the	O
same	O
communication	O
.	O
</s>
<s>
Binary	O
session	B-Operating_System
types	I-Operating_System
can	O
be	O
described	O
using	O
send	O
operations	O
(	O
)	O
,	O
receive	O
operations	O
(	O
)	O
,	O
branches	O
(	O
)	O
,	O
selections	O
(	O
)	O
,	O
recursion	O
(	O
)	O
and	O
termination	O
(	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
represents	O
a	O
session	B-Operating_System
type	I-Operating_System
which	O
first	O
sends	O
a	O
boolean	O
(	O
)	O
,	O
then	O
receives	O
an	O
integer	O
(	O
)	O
before	O
finally	O
terminating	O
(	O
)	O
.	O
</s>
<s>
Session	B-Operating_System
types	I-Operating_System
have	O
been	O
adapted	O
for	O
several	O
existing	O
programming	O
languages	O
,	O
including	O
:	O
</s>
