<s>
Prospective	B-General_Concept
search	I-General_Concept
,	O
or	O
persistent	O
search	O
,	O
is	O
a	O
method	O
of	O
searching	B-Application
which	O
determines	O
which	O
of	O
a	O
set	O
of	O
queries	O
matches	O
content	O
in	O
a	O
corpus	O
.	O
</s>
<s>
This	O
differs	O
from	O
traditional	O
,	O
or	O
"	O
retrospective	O
"	O
,	O
search	O
such	O
as	O
search	B-Application
engines	I-Application
,	O
where	O
the	O
information	O
for	O
the	O
results	O
is	O
acquired	O
and	O
then	O
queried	O
.	O
</s>
<s>
In	O
contrast	O
,	O
prospective	B-General_Concept
search	I-General_Concept
starts	O
with	O
the	O
user	O
's	O
queries	O
,	O
gathers	O
the	O
information	O
in	O
a	O
targeted	O
way	O
,	O
indexes	O
it	O
,	O
and	O
then	O
provides	O
results	O
as	O
they	O
arrive	O
.	O
</s>
<s>
One	O
implementation	O
of	O
prospective	B-General_Concept
search	I-General_Concept
is	O
as	O
saved	O
searches	O
which	O
are	O
re-run	O
when	O
new	O
content	O
is	O
acquired	O
.	O
</s>
<s>
Prospective	B-General_Concept
search	I-General_Concept
is	O
well	O
suited	O
to	O
queries	O
where	O
the	O
results	O
change	O
over	O
time	O
,	O
such	O
as	O
the	O
current	O
news	O
,	O
blogs	O
,	O
and	O
trends	O
.	O
</s>
