<s>
TrueSkill	B-Device
is	O
a	O
skill-based	O
ranking	O
system	O
developed	O
by	O
Microsoft	O
for	O
use	O
with	O
video	O
game	O
matchmaking	O
on	O
Xbox	B-Application
Live	I-Application
.	O
</s>
<s>
Unlike	O
the	O
popular	O
Elo	O
rating	O
system	O
,	O
which	O
was	O
initially	O
designed	O
for	O
chess	B-Application
,	O
TrueSkill	B-Device
is	O
designed	O
to	O
support	O
games	O
with	O
more	O
than	O
two	O
players	O
.	O
</s>
<s>
In	O
2018	O
,	O
Microsoft	O
published	O
details	O
about	O
an	O
extended	O
version	O
of	O
TrueSkill	B-Device
,	O
named	O
TrueSkill2	O
.	O
</s>
<s>
On	O
Xbox	B-Application
Live	I-Application
,	O
players	O
start	O
with	O
and	O
;	O
always	O
increases	O
after	O
a	O
win	O
and	O
always	O
decreases	O
after	O
a	O
loss	O
.	O
</s>
<s>
Factor	O
graphs	O
and	O
expectation	B-General_Concept
propagation	I-General_Concept
via	O
moment	O
matching	O
are	O
used	O
to	O
compute	O
the	O
message	O
passing	O
equations	O
which	O
in	O
turn	O
compute	O
the	O
skills	O
for	O
the	O
players	O
.	O
</s>
<s>
The	O
system	O
can	O
be	O
used	O
with	O
arbitrary	O
scales	O
,	O
but	O
Microsoft	O
uses	O
a	O
scale	O
from	O
0	O
to	O
50	O
for	O
Xbox	B-Application
Live	I-Application
.	O
</s>
<s>
TrueSkill	B-Device
is	O
patented	O
,	O
and	O
the	O
name	O
is	O
trademarked	O
,	O
so	O
it	O
is	O
limited	O
to	O
Microsoft	O
projects	O
and	O
commercial	O
projects	O
that	O
obtain	O
a	O
license	O
to	O
use	O
the	O
algorithm	O
.	O
</s>
