<s>
Zen	O
(	O
)	O
is	O
a	O
personal	B-Application
recommendations	I-Application
service	O
created	O
by	O
Yandex	O
that	O
uses	O
machine	O
learning	O
technology	O
.	O
</s>
<s>
Zen	O
creates	O
a	O
feed	B-General_Concept
of	I-General_Concept
content	I-General_Concept
that	O
automatically	O
adjusts	O
to	O
the	O
interests	O
of	O
a	O
user	O
.	O
</s>
<s>
The	O
selection	O
of	O
content	O
is	O
based	O
on	O
the	O
analysis	O
of	O
browsing	B-Application
history	I-Application
,	O
user-specified	O
preferences	O
,	O
location	O
,	O
time	O
of	O
day	O
and	O
other	O
factors	O
.	O
</s>
<s>
In	O
1997	O
,	O
Yandex	O
began	O
research	O
into	O
natural	B-Language
language	I-Language
processing	I-Language
,	O
machine	O
learning	O
and	O
recommendation	B-Application
systems	I-Application
.	O
</s>
<s>
In	O
2009	O
,	O
the	O
proprietary	O
machine	O
learning	O
algorithm	O
MatrixNet	B-Application
was	O
developed	O
by	O
Yandex	O
,	O
becoming	O
one	O
of	O
the	O
key	O
components	O
that	O
Zen	O
functions	O
on	O
.	O
</s>
<s>
At	O
first	O
,	O
the	O
Zen	O
content	O
feed	O
showed	O
only	O
content	O
from	O
the	O
media	O
,	O
and	O
the	O
service	O
was	O
only	O
available	O
to	O
the	O
5%	O
of	O
users	O
of	O
Yandex	O
Browser	B-Application
on	O
Android	B-Application
that	O
had	O
registered	O
a	O
Yandex	O
account	O
.	O
</s>
<s>
In	O
the	O
following	O
months	O
,	O
other	O
types	O
of	O
content	O
were	O
added	O
to	O
Zen	O
,	O
such	O
as	O
image	O
galleries	O
,	O
articles	O
,	O
blogs	O
,	O
forums	O
,	O
videos	O
from	O
YouTube	B-General_Concept
,	O
etc	O
.	O
</s>
<s>
Apple	O
and	O
Facebook	B-Application
have	O
also	O
launched	O
news	O
services	O
with	O
similar	O
functionality	O
.	O
</s>
