<s>
A	O
search	B-Application
aggregator	I-Application
is	O
a	O
type	O
of	O
metasearch	B-Application
engine	I-Application
which	O
gathers	O
results	O
from	O
multiple	O
search	O
engines	O
simultaneously	O
,	O
typically	O
through	O
RSS	O
search	O
results	O
.	O
</s>
<s>
It	O
combines	O
user	O
specified	O
search	O
feeds	O
(	O
parameterized	O
RSS	O
feeds	O
which	O
return	O
search	O
results	O
)	O
to	O
give	O
the	O
user	O
the	O
same	O
level	O
of	O
control	O
over	O
content	O
as	O
a	O
general	O
aggregator	B-Application
.	O
</s>
<s>
Search	B-Application
aggregators	I-Application
are	O
an	O
increasingly	O
popular	O
way	O
to	O
take	O
advantage	O
of	O
the	O
power	O
of	O
multiple	O
search	O
engines	O
with	O
a	O
flexibility	O
not	O
seen	O
in	O
traditional	O
metasearch	B-Application
engines	I-Application
.	O
</s>
<s>
To	O
the	O
end	O
user	O
,	O
a	O
search	B-Application
aggregator	I-Application
may	O
appear	O
to	O
be	O
just	O
a	O
customizable	O
search	O
engine	O
and	O
the	O
use	O
of	O
RSS	O
may	O
be	O
completely	O
hidden	O
.	O
</s>
<s>
However	O
,	O
the	O
presence	O
of	O
RSS	O
is	O
directly	O
responsible	O
for	O
the	O
existence	O
of	O
search	B-Application
aggregators	I-Application
and	O
a	O
critical	O
component	O
in	O
the	O
behind-the-scenes	O
technology	O
.	O
</s>
<s>
In	O
2005	O
Amazon	O
published	O
the	O
OpenSearch	B-Application
specification	O
for	O
making	O
search	O
results	O
available	O
in	O
a	O
generic	O
XML	O
format	O
.	O
</s>
<s>
While	O
many	O
sites	O
currently	O
publish	O
results	O
in	O
OpenSearch	B-Application
,	O
many	O
simply	O
publish	O
in	O
generic	O
RSS	O
format	O
.	O
</s>
<s>
However	O
,	O
while	O
OpenSearch	B-Application
syndication	O
allows	O
for	O
greater	O
flexibility	O
in	O
the	O
way	O
Search	B-Application
Aggregators	I-Application
display	O
results	O
,	O
it	O
is	O
generally	O
not	O
required	O
.	O
</s>
<s>
A	O
search	B-Application
aggregator	I-Application
typically	O
allows	O
users	O
to	O
select	O
specific	O
search	O
engines	O
ad	O
hoc	O
to	O
perform	O
a	O
specified	O
query	O
.	O
</s>
<s>
At	O
the	O
time	O
the	O
user	O
enters	O
the	O
query	O
into	O
the	O
Search	B-Application
Aggregator	I-Application
,	O
it	O
generates	O
the	O
required	O
URL	O
"	O
on	O
the	O
fly	O
"	O
by	O
inserting	O
the	O
search	O
query	O
into	O
the	O
parameterized	O
URL	O
for	O
the	O
search	O
feed	O
.	O
</s>
<s>
The	O
Search	B-Application
Aggregator	I-Application
would	O
then	O
parse	O
the	O
results	O
and	O
display	O
them	O
in	O
a	O
user-friendly	O
way	O
.	O
</s>
<s>
This	O
system	O
has	O
several	O
advantages	O
over	O
traditional	O
metasearch	B-Application
engines	I-Application
.	O
</s>
<s>
They	O
also	O
allow	O
for	O
easy	O
addition	O
of	O
new	O
engines	O
to	O
the	O
users	O
personal	O
collection	O
(	O
similar	O
to	O
the	O
way	O
a	O
user	O
adds	O
a	O
new	O
news	O
feed	O
to	O
a	O
news	B-Application
aggregator	I-Application
.	O
)	O
</s>
