<s>
In	O
machine	O
learning	O
and	O
natural	B-Language
language	I-Language
processing	I-Language
,	O
the	O
pachinko	B-General_Concept
allocation	I-General_Concept
model	O
(	O
PAM	O
)	O
is	O
a	O
topic	O
model	O
.	O
</s>
<s>
While	O
first	O
described	O
and	O
implemented	O
in	O
the	O
context	O
of	O
natural	B-Language
language	I-Language
processing	I-Language
,	O
the	O
algorithm	O
may	O
have	O
applications	O
in	O
other	O
fields	O
such	O
as	O
bioinformatics	O
.	O
</s>
<s>
Pachinko	B-General_Concept
allocation	I-General_Concept
was	O
first	O
described	O
by	O
Wei	O
Li	O
and	O
Andrew	O
McCallum	O
in	O
2006	O
.	O
</s>
<s>
The	O
idea	O
was	O
extended	O
with	O
hierarchical	O
Pachinko	B-General_Concept
allocation	I-General_Concept
by	O
Li	O
,	O
McCallum	O
,	O
and	O
David	O
Mimno	O
in	O
2007	O
.	O
</s>
<s>
The	O
algorithm	O
has	O
been	O
implemented	O
in	O
the	O
MALLET	B-Language
software	O
package	O
published	O
by	O
McCallum	O
's	O
group	O
at	O
the	O
University	O
of	O
Massachusetts	O
Amherst	O
.	O
</s>
