<s>
Xapian	B-Application
is	O
a	O
free	B-License
and	I-License
open-source	I-License
probabilistic	O
information	B-Library
retrieval	I-Library
library	O
,	O
released	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
(	O
GPL	B-License
)	O
.	O
</s>
<s>
It	O
is	O
a	O
full-text	O
search	B-Application
engine	O
library	O
for	O
programmers	O
.	O
</s>
<s>
It	O
is	O
written	O
in	O
C++	B-Language
,	O
with	O
bindings	O
to	O
allow	O
use	O
from	O
Perl	B-Language
,	O
Python	B-Language
(	O
2	O
and	O
3	O
)	O
,	O
PHP	B-Application
(	O
5	O
and	O
7	O
)	O
,	O
Java	B-Device
,	O
Tcl	B-Operating_System
,	O
C#	B-Application
,	O
Ruby	B-Language
,	O
Lua	B-Language
,	O
Erlang	B-Operating_System
,	O
Node.js	B-Language
and	O
R	B-Language
.	O
Xapian	B-Application
is	O
highly	O
portable	O
and	O
runs	O
on	O
Linux	B-Application
,	O
OS	B-Operating_System
X	I-Operating_System
,	O
FreeBSD	B-Operating_System
,	O
NetBSD	B-Device
,	O
OpenBSD	B-Operating_System
,	O
Solaris	B-Application
,	O
HP-UX	B-Application
,	O
AIX	B-Application
,	O
Windows	B-Application
,	O
OS/2	B-Application
and	O
Hurd	B-Application
,	O
as	O
well	O
as	O
Tru64	B-Operating_System
.	O
</s>
<s>
Xapian	B-Application
grew	O
out	O
of	O
the	O
Muscat	O
search	B-Application
engine	O
,	O
written	O
by	O
Dr.	O
Martin	O
F	O
.	O
Porter	O
at	O
the	O
University	O
of	O
Cambridge	O
.	O
</s>
<s>
The	O
first	O
official	O
release	O
of	O
Xapian	B-Application
was	O
version	O
0.5.0	O
on	O
September	O
20	O
,	O
2002	O
.	O
</s>
<s>
Xapian	B-Application
allows	O
developers	O
to	O
add	O
advanced	O
indexing	O
and	O
search	B-Application
facilities	O
to	O
their	O
own	O
applications	O
.	O
</s>
<s>
Organisations	O
and	O
projects	O
using	O
Xapian	B-Application
include	O
the	O
Library	O
of	O
the	O
University	O
of	O
Cologne	O
,	O
Debian	O
,	O
Die	O
Zeit	O
,	O
MoinMoin	B-Application
,	O
and	O
One	O
Laptop	O
per	O
Child	O
.	O
</s>
<s>
Simultaneous	O
search	B-Application
and	O
update	O
,	O
with	O
new	O
documents	O
being	O
immediately	O
visible	O
.	O
</s>
<s>
Support	O
for	O
large	O
databases	O
:	O
Xapian	B-Application
has	O
been	O
proven	O
to	O
scale	O
to	O
hundreds	O
of	O
millions	O
of	O
documents	O
.	O
</s>
<s>
Phrase	O
and	O
proximity	B-Application
searching	I-Application
.	O
</s>
<s>
Relevance	B-Application
feedback	I-Application
,	O
which	O
improves	O
ranking	O
and	O
can	O
expand	O
a	O
query	B-Library
,	O
find	O
related	O
documents	O
,	O
categorise	O
documents	O
etc	O
.	O
</s>
<s>
Structured	O
Boolean	O
queries	B-Library
,	O
e.g.	O
</s>
<s>
Wildcard	O
search	B-Application
,	O
e.g.	O
</s>
<s>
Omega	O
,	O
a	O
packaged	O
solution	O
for	O
adding	O
a	O
search	B-Application
engine	O
to	O
a	O
web	O
site	O
or	O
intranet	O
.	O
</s>
