<s>
mod_oai	O
is	O
an	O
Apache	B-Application
module	I-Application
that	O
allows	O
web	B-Application
crawlers	I-Application
to	O
efficiently	O
discover	O
new	O
,	O
modified	O
,	O
and	O
deleted	O
web	O
resources	O
from	O
a	O
web	B-Application
server	I-Application
by	O
using	O
OAI-PMH	O
,	O
a	O
protocol	O
which	O
is	O
widely	O
used	O
in	O
the	O
digital	O
libraries	O
community	O
.	O
</s>
<s>
mod_oai	O
also	O
allows	O
harvesters	O
to	O
obtain	O
"	O
archive-ready	O
"	O
resources	O
from	O
a	O
web	B-Application
server	I-Application
.	O
</s>
<s>
mod_oai	O
is	O
developed	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
(	O
GPL	B-License
)	O
,	O
and	O
is	O
distributed	O
free	O
of	O
charge	O
.	O
</s>
