<s>
Document	B-Algorithm
classification	I-Algorithm
or	O
document	B-Algorithm
categorization	I-Algorithm
is	O
a	O
problem	O
in	O
library	O
science	O
,	O
information	O
science	O
and	O
computer	B-General_Concept
science	I-General_Concept
.	O
</s>
<s>
The	O
intellectual	O
classification	O
of	O
documents	O
has	O
mostly	O
been	O
the	O
province	O
of	O
library	O
science	O
,	O
while	O
the	O
algorithmic	O
classification	O
of	O
documents	O
is	O
mainly	O
in	O
information	O
science	O
and	O
computer	B-General_Concept
science	I-General_Concept
.	O
</s>
<s>
The	O
problems	O
are	O
overlapping	O
,	O
however	O
,	O
and	O
there	O
is	O
therefore	O
interdisciplinary	O
research	O
on	O
document	B-Algorithm
classification	I-Algorithm
.	O
</s>
<s>
When	O
not	O
otherwise	O
specified	O
,	O
text	B-Algorithm
classification	I-Algorithm
is	O
implied	O
.	O
</s>
<s>
The	O
classifier	O
asks	O
themself	O
:	O
“	O
Under	O
which	O
descriptors	O
should	O
this	O
entity	O
be	O
found	O
?	O
”	O
and	O
“	O
think	O
of	O
all	O
the	O
possible	O
queries	B-Library
and	O
decide	O
for	O
which	O
ones	O
the	O
entity	O
at	O
hand	O
is	O
relevant	O
”	O
(	O
Soergel	O
,	O
1985	O
,	O
p.230	O
)	O
.	O
</s>
<s>
Automatic	O
document	B-Algorithm
classification	I-Algorithm
tasks	O
can	O
be	O
divided	O
into	O
three	O
sorts	O
:	O
supervised	B-Algorithm
document	I-Algorithm
classification	I-Algorithm
where	O
some	O
external	O
mechanism	O
(	O
such	O
as	O
human	O
feedback	O
)	O
provides	O
information	O
on	O
the	O
correct	O
classification	O
for	O
documents	O
,	O
unsupervised	B-Algorithm
document	I-Algorithm
classification	I-Algorithm
(	O
also	O
known	O
as	O
document	O
clustering	O
)	O
,	O
where	O
the	O
classification	O
must	O
be	O
done	O
entirely	O
without	O
reference	O
to	O
external	O
information	O
,	O
and	O
semi-supervised	O
document	B-Algorithm
classification	I-Algorithm
,	O
where	O
parts	O
of	O
the	O
documents	O
are	O
labeled	O
by	O
the	O
external	O
mechanism	O
.	O
</s>
<s>
Automatic	O
document	B-Algorithm
classification	I-Algorithm
techniques	O
include	O
:	O
</s>
