<s>
Taxonomy	B-Application
for	I-Application
search	I-Application
engines	I-Application
refers	O
to	O
classification	O
methods	O
that	O
improve	O
relevance	O
in	O
vertical	B-Application
search	I-Application
.	O
</s>
<s>
Taxonomies	O
of	O
entities	O
are	O
tree	O
structures	O
whose	O
nodes	O
are	O
labelled	O
with	O
entities	O
likely	O
to	O
occur	O
in	O
a	O
web	O
search	O
query	B-Library
.	O
</s>
<s>
Searches	O
use	O
these	O
trees	O
to	O
match	O
keywords	O
from	O
a	O
search	O
query	B-Library
to	O
keywords	O
from	O
answers	O
(	O
or	O
snippets	O
)	O
.	O
</s>
<s>
Taxonomies	O
,	O
thesauri	O
and	O
concept	O
hierarchies	O
are	O
crucial	O
components	O
for	O
many	O
applications	O
of	O
information	B-Library
retrieval	I-Library
,	O
natural	B-Language
language	I-Language
processing	I-Language
and	O
knowledge	O
management	O
.	O
</s>
<s>
A	O
number	O
of	O
studies	O
proposed	O
the	O
automated	B-General_Concept
building	I-General_Concept
of	I-General_Concept
taxonomies	I-General_Concept
based	O
on	O
linguistic	O
resources	O
and/or	O
statistical	O
machine	O
learning	O
.	O
</s>
