<s>
A	O
discovery	B-Library
system	I-Library
is	O
a	O
bibliographic	B-Library
search	I-Library
system	I-Library
based	O
on	O
search	O
engine	O
technology	O
.	O
</s>
<s>
The	O
results	O
from	O
searching	O
a	O
discovery	B-Library
system	I-Library
may	O
include	O
books	O
and	O
other	O
print	O
materials	O
from	O
the	O
library	O
's	O
catalog	B-Library
,	O
electronic	O
resources	O
such	O
as	O
e-journals	O
or	O
videos	O
,	O
and	O
items	O
stored	O
in	O
other	O
libraries	O
.	O
</s>
<s>
The	O
term	O
discovery	B-Library
layer	I-Library
has	O
been	O
described	O
as	O
an	O
overarching	O
term	O
that	O
can	O
include	O
:	O
</s>
<s>
,	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
that	O
library	O
users	O
search	O
or	O
browse	O
with	O
.	O
</s>
<s>
It	O
includes	O
search-engine	O
like	O
amenities	O
such	O
as	O
spelling	O
correction	O
,	O
tolerance	O
for	O
punctuation	O
differences	O
,	O
and	O
typeahead	B-Application
search	I-Application
.	O
</s>
<s>
This	O
idea	O
is	O
also	O
called	O
a	O
next-generation	O
catalog	B-Library
.	O
</s>
<s>
,	O
an	O
interconnected	O
search	O
system	O
,	O
allowing	O
library	O
users	O
to	O
search	O
not	O
only	O
the	O
catalog	B-Library
of	O
library	O
print	O
materials	O
,	O
but	O
various	O
digital	O
resources	O
and	O
perhaps	O
resources	O
located	O
in	O
other	O
libraries	O
.	O
</s>
<s>
The	O
discovery	B-Library
system	I-Library
queries	O
more	O
than	O
one	O
data	O
source	O
upon	O
a	O
single	O
user	O
request	O
;	O
this	O
is	O
sometimes	O
called	O
federated	B-Operating_System
search	I-Operating_System
.	O
</s>
<s>
The	O
term	O
indicates	O
that	O
the	O
software	O
is	O
modular	O
and	O
can	O
be	O
used	O
to	O
emphasize	O
the	O
separability	O
of	O
catalog	B-Library
search	O
and	O
browse	O
functionality	O
from	O
an	O
integrated	O
library	O
system	O
(	O
ILS	O
)	O
.	O
</s>
<s>
Users	O
searching	O
for	O
print	O
materials	O
(	O
such	O
as	O
books	O
)	O
at	O
a	O
library	O
once	O
used	O
card	B-Library
catalogs	I-Library
,	O
and	O
later	O
computerized	O
catalogs	O
called	O
OPACs	O
.	O
</s>
<s>
Searching	O
for	O
resources	O
other	O
than	O
material	O
in	O
the	O
catalog	B-Library
,	O
such	O
as	O
electronic	O
resources	O
,	O
was	O
(	O
or	O
is	O
)	O
done	O
with	O
separate	O
tools	O
.	O
</s>
<s>
The	O
resulting	O
monolithic	B-General_Concept
software	O
systems	O
were	O
named	O
integrated	O
library	O
systems	O
.	O
</s>
<s>
Reference	O
librarians	O
in	O
the	O
mid-2000s	O
also	O
spent	O
"	O
a	O
lot	O
of	O
time	O
talking	O
about	O
information	B-Application
silos	I-Application
"	O
.	O
</s>
<s>
One	O
author	O
dates	O
the	O
uniting	O
of	O
these	O
features	O
to	O
2009	O
;	O
this	O
would	O
be	O
the	O
invention	O
of	O
the	O
discovery	B-Library
system	I-Library
.	O
</s>
<s>
Particularly	O
if	O
decoupled	O
from	O
an	O
ILS	O
,	O
this	O
united	O
product	O
can	O
also	O
be	O
called	O
a	O
discovery	B-Library
layer	I-Library
.	O
</s>
<s>
The	O
discovery	B-Library
layer	I-Library
can	O
be	O
looked	O
on	O
as	O
the	O
replacement	O
for	O
the	O
OPAC	O
.	O
</s>
<s>
Some	O
libraries	O
maintain	O
both	O
a	O
catalog	B-Library
interface	O
OPAC	O
and	O
a	O
discovery	B-Library
layer	I-Library
interface	O
.	O
</s>
<s>
Large	O
search	O
space	O
:	O
A	O
search	O
can	O
search	O
the	O
data	O
from	O
different	O
data	O
sources	O
(	O
the	O
discovery	B-Library
system	I-Library
has	O
a	O
comprehensive	O
central	O
subject	O
index	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
you	O
can	O
search	O
a	O
journal	O
article	O
or	O
a	O
textbook	O
directly	O
in	O
the	O
discovery	B-Library
system	I-Library
and	O
you	O
do	O
not	O
have	O
to	O
change	O
from	O
a	O
subject	O
database	O
to	O
the	O
library	B-Library
catalog	I-Library
.	O
</s>
<s>
For	O
example	O
,	O
links	O
to	O
similar	O
hits	O
,	O
entries	O
in	O
subject	B-Library
databases	I-Library
,	O
or	O
Wikipedia	O
articles	O
are	O
displayed	O
(	O
integration	O
of	O
other	O
web	O
technologies	O
)	O
.	O
</s>
<s>
Some	O
discovery	B-Library
layer	I-Library
or	O
discovery	O
service	O
products	O
are	O
modules	O
of	O
a	O
particular	O
ILS	O
or	O
database	O
product	O
,	O
and	O
are	O
sold	O
by	O
that	O
product	O
's	O
vendor	O
:	O
an	O
example	O
is	O
EBSCO	B-Library
Discovery	O
Service	O
.	O
</s>
<s>
Other	O
discovery	B-Library
tools	I-Library
are	O
free-standing	O
software	O
products	O
:	O
Blacklight	B-Application
and	O
VuFind	B-Language
are	O
open-source	B-Application
examples	O
.	O
</s>
<s>
Open-source	B-Application
products	O
:	O
</s>
