<s>
In	O
machine	O
learning	O
,	O
semantic	B-General_Concept
analysis	I-General_Concept
of	O
a	O
corpus	O
is	O
the	O
task	O
of	O
building	O
structures	O
that	O
approximate	O
concepts	O
from	O
a	O
large	O
set	O
of	O
documents	O
.	O
</s>
<s>
Latent	O
semantic	B-General_Concept
analysis	I-General_Concept
(	O
sometimes	O
latent	O
semantic	O
indexing	O
)	O
,	O
is	O
a	O
class	O
of	O
techniques	O
where	O
documents	O
are	O
represented	O
as	O
vectors	B-Language
in	O
term	O
space	O
.	O
</s>
<s>
A	O
prominent	O
example	O
is	O
PLSI	B-General_Concept
.	O
</s>
<s>
n-grams	B-Language
and	O
hidden	O
Markov	O
models	O
work	O
by	O
representing	O
the	O
term	O
stream	O
as	O
a	O
Markov	O
chain	O
where	O
each	O
term	O
is	O
derived	O
from	O
the	O
few	O
terms	O
before	O
it	O
.	O
</s>
