<s>
A	O
vertical	B-Application
search	I-Application
engine	I-Application
is	O
distinct	O
from	O
a	O
general	O
web	B-Application
search	I-Application
engine	I-Application
,	O
in	O
that	O
it	O
focuses	O
on	O
a	O
specific	O
segment	O
of	O
online	O
content	O
.	O
</s>
<s>
They	O
are	O
also	O
called	O
specialty	O
or	O
topical	O
search	B-Application
engines	I-Application
.	O
</s>
<s>
Examples	O
of	O
vertical	B-Application
search	I-Application
engines	I-Application
include	O
the	O
Library	O
of	O
Congress	O
,	O
Mocavo	O
,	O
Nuroa	O
,	O
Trulia	O
,	O
and	O
Yelp	B-Application
.	O
</s>
<s>
In	O
contrast	O
to	O
general	O
web	B-Application
search	I-Application
engines	I-Application
,	O
which	O
attempt	O
to	O
index	B-Application
large	O
portions	O
of	O
the	O
World	O
Wide	O
Web	O
using	O
a	O
web	B-Application
crawler	I-Application
,	O
vertical	B-Application
search	I-Application
engines	I-Application
typically	O
use	O
a	O
focused	B-Protocol
crawler	I-Protocol
which	O
attempts	O
to	O
index	B-Application
only	O
relevant	O
web	O
pages	O
to	O
a	O
pre-defined	O
topic	O
or	O
set	O
of	O
topics	O
.	O
</s>
<s>
Some	O
vertical	B-Application
search	I-Application
sites	O
focus	O
on	O
individual	O
verticals	O
,	O
while	O
other	O
sites	O
include	O
multiple	O
vertical	B-Application
searches	I-Application
within	O
one	O
search	B-Application
engine	I-Application
.	O
</s>
<s>
Vertical	B-Application
search	I-Application
offers	O
several	O
potential	O
benefits	O
over	O
general	O
search	B-Application
engines	I-Application
:	O
</s>
<s>
Leverage	O
domain	O
knowledge	O
including	O
taxonomies	B-Application
and	O
ontologies	B-Language
,	O
</s>
<s>
Vertical	B-Application
search	I-Application
can	O
be	O
viewed	O
as	O
similar	O
to	O
enterprise	B-Application
search	I-Application
where	O
the	O
domain	O
of	O
focus	O
is	O
the	O
enterprise	O
,	O
such	O
as	O
a	O
company	O
,	O
government	O
or	O
other	O
organization	O
.	O
</s>
<s>
In	O
2013	O
,	O
consumer	O
price	O
comparison	O
websites	O
with	O
integrated	O
vertical	B-Application
search	I-Application
engines	I-Application
such	O
as	O
FindTheBest	O
drew	O
large	O
rounds	O
of	O
venture	O
capital	O
funding	O
,	O
indicating	O
a	O
growth	O
trend	O
for	O
these	O
applications	O
of	O
vertical	B-Application
search	I-Application
technology	O
.	O
</s>
<s>
Domain-specific	B-Application
search	I-Application
solutions	O
focus	O
on	O
one	O
area	O
of	O
knowledge	O
,	O
creating	O
customized	O
search	O
experiences	O
,	O
that	O
because	O
of	O
the	O
domain	O
's	O
limited	O
corpus	O
and	O
clear	O
relationships	O
between	O
concepts	O
,	O
provide	O
extremely	O
relevant	O
results	O
for	O
searchers	O
.	O
</s>
<s>
Any	O
general	O
search	B-Application
engine	I-Application
would	O
be	O
indexing	O
all	O
the	O
pages	O
and	O
searches	O
in	O
a	O
breadth-first	B-Algorithm
manner	O
to	O
collect	O
documents	O
.	O
</s>
<s>
The	O
spidering	B-Application
in	O
domain-specific	B-Application
search	I-Application
engines	O
more	O
efficiently	O
searches	O
a	O
small	O
subset	O
of	O
documents	O
by	O
focusing	O
on	O
a	O
particular	O
set	O
.	O
</s>
<s>
Spidering	B-Application
accomplished	O
with	O
a	O
reinforcement-learning	O
framework	O
has	O
been	O
found	O
to	O
be	O
three	O
times	O
more	O
efficient	O
than	O
breadth-first	B-Algorithm
search	I-Algorithm
.	O
</s>
<s>
DARPA	O
wants	O
the	O
Memex	O
technology	O
developed	O
in	O
this	O
research	O
to	O
be	O
usable	O
for	O
search	B-Application
engines	I-Application
that	O
can	O
search	O
for	O
information	O
on	O
the	O
Deep	O
Web	O
–	O
the	O
part	O
of	O
the	O
Internet	O
that	O
is	O
largely	O
unreachable	O
by	O
commercial	O
search	B-Application
engines	I-Application
like	O
Google	B-Application
or	O
Yahoo	B-Application
.	O
</s>
<s>
DARPA	O
intends	O
for	O
the	O
program	O
to	O
replace	O
the	O
centralized	O
procedures	O
used	O
by	O
commercial	O
search	B-Application
engines	I-Application
,	O
stating	O
that	O
the	O
"	O
creation	O
of	O
a	O
new	O
domain-specific	O
indexing	O
and	O
search	O
paradigm	O
will	O
provide	O
mechanisms	O
for	O
improved	O
content	O
discovery	O
,	O
information	O
extraction	O
,	O
information	O
retrieval	O
,	O
user	O
collaboration	O
,	O
and	O
extension	O
of	O
current	O
search	O
capabilities	O
to	O
the	O
deep	O
web	O
,	O
the	O
dark	O
web	O
,	O
and	O
nontraditional	O
(	O
e.g.	O
</s>
