<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
phrase	O
searching	O
allows	O
users	O
to	O
retrieve	O
content	O
from	O
information	O
systems	O
(	O
such	O
as	O
documents	O
from	O
file	O
storage	O
systems	O
,	O
records	O
from	O
databases	O
,	O
and	O
web	O
pages	O
on	O
the	O
internet	O
)	O
that	O
contains	O
a	O
specific	O
order	O
and	O
combination	O
of	O
words	O
defined	O
by	O
the	O
user	O
.	O
</s>
<s>
Phrase	B-Algorithm
search	I-Algorithm
is	O
one	O
of	O
many	O
search	O
operators	O
that	O
are	O
standard	O
in	O
search	B-Application
engine	I-Application
technology	I-Application
,	O
along	O
with	O
Boolean	O
operators	O
(	O
AND	O
,	O
OR	O
,	O
and	O
NOT	O
)	O
,	O
truncation	O
and	O
wildcard	O
operators	O
(	O
commonly	O
represented	O
by	O
the	O
asterisk	O
symbol	O
)	O
,	O
field	O
code	O
operators	O
(	O
which	O
look	O
for	O
specific	O
words	O
in	O
defined	O
fields	O
,	O
such	O
as	O
the	O
Author	O
field	O
in	O
a	O
periodical	O
database	O
)	O
,	O
and	O
proximity	O
operators	O
(	O
which	O
look	O
for	O
defined	O
words	O
that	O
appear	O
close	O
to	O
one	O
another	O
,	O
if	O
not	O
directly	O
next	O
to	O
each	O
other	O
as	O
in	O
a	O
phrase	B-Algorithm
search	I-Algorithm
)	O
.	O
</s>
<s>
Search	O
operators	O
are	O
used	O
to	O
refine	O
a	O
search	O
when	O
a	O
simple	O
keyword	B-Application
search	I-Application
provides	O
too	O
many	O
unwanted	O
results	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
search	O
for	O
red	O
apple	O
may	O
return	O
records	O
that	O
contain	O
the	O
word	O
"	O
apple	O
,	O
"	O
ones	O
that	O
contain	O
"	O
red	O
,	O
"	O
and	O
ones	O
that	O
contain	O
both	O
words	O
no	O
matter	O
where	O
in	O
the	O
record	O
they	O
appear	O
(	O
that	O
is	O
,	O
assuming	O
the	O
search	O
engine	O
applies	O
Boolean	O
OR	O
logic	O
to	O
its	O
keyword	B-Application
search	I-Application
function	O
)	O
,	O
whereas	O
a	O
search	O
for	O
"	O
red	O
apple	O
"	O
will	O
only	O
return	O
records	O
that	O
contain	O
the	O
phrase	O
"	O
red	O
apple.	O
"	O
</s>
<s>
Phrase	B-Algorithm
search	I-Algorithm
is	O
one	O
of	O
the	O
more	O
important	O
techniques	O
associated	O
with	O
optimizing	O
the	O
textual	O
content	O
of	O
web	O
pages	O
in	O
such	O
a	O
way	O
that	O
it	O
is	O
likely	O
to	O
be	O
found	O
by	O
someone	O
searching	O
for	O
a	O
certain	O
string	O
of	O
text	O
.	O
</s>
