<s>
An	O
extranet	B-Architecture
is	O
a	O
controlled	O
private	O
network	O
that	O
allows	O
access	O
to	O
partners	O
,	O
vendors	O
and	O
suppliers	O
or	O
an	O
authorized	O
set	O
of	O
customers	O
–	O
normally	O
to	O
a	O
subset	O
of	O
the	O
information	O
accessible	O
from	O
an	O
organization	O
's	O
intranet	B-General_Concept
.	O
</s>
<s>
An	O
extranet	B-Architecture
is	O
similar	O
to	O
a	O
DMZ	B-General_Concept
in	O
that	O
it	O
provides	O
access	O
to	O
needed	O
services	O
for	O
authorized	O
parties	O
,	O
without	O
granting	O
access	O
to	O
an	O
organization	O
's	O
entire	O
network	O
.	O
</s>
<s>
Historically	O
,	O
the	O
term	O
was	O
occasionally	O
also	O
used	O
in	O
the	O
sense	O
of	O
two	O
organizations	O
sharing	O
their	O
internal	B-General_Concept
networks	I-General_Concept
over	O
a	O
virtual	B-Application
private	I-Application
network	I-Application
(	O
VPN	B-Application
)	O
.	O
</s>
<s>
During	O
the	O
late	O
1990s	O
and	O
early	O
2000s	O
,	O
several	O
industries	O
started	O
to	O
use	O
the	O
term	O
'	O
extranet	B-Architecture
 '	O
to	O
describe	O
centralized	O
repositories	O
of	O
shared	O
data	O
(	O
and	O
supporting	O
applications	O
)	O
made	O
accessible	O
via	O
the	O
web	O
only	O
to	O
authorized	O
members	O
of	O
particular	O
work	O
groups	O
-	O
for	O
example	O
,	O
geographically	O
dispersed	O
,	O
multi-company	O
project	O
teams	O
.	O
</s>
<s>
Some	O
applications	O
are	O
offered	O
on	O
a	O
software	B-Architecture
as	I-Architecture
a	I-Architecture
service	I-Architecture
(	O
SaaS	B-Architecture
)	O
basis	O
.	O
</s>
<s>
For	O
example	O
,	O
in	O
the	O
construction	O
industry	O
,	O
project	O
teams	O
may	O
access	O
a	O
project	O
extranet	B-Architecture
to	O
share	O
drawings	O
,	O
photographs	O
and	O
documents	O
,	O
and	O
use	O
online	O
applications	O
to	O
mark-up	O
and	O
make	O
comments	O
and	O
to	O
manage	O
and	O
report	O
on	O
project-related	O
communications	O
.	O
</s>
<s>
Extranets	B-Architecture
can	O
be	O
expensive	O
to	O
implement	O
and	O
maintain	O
within	O
an	O
organization	O
(	O
e.g.	O
,	O
hardware	O
,	O
software	O
,	O
employee	O
training	O
costs	O
)	O
,	O
if	O
hosted	O
internally	O
rather	O
than	O
by	O
an	O
application	O
service	O
provider	O
.	O
</s>
<s>
Security	O
of	O
extranets	B-Architecture
can	O
be	O
a	O
concern	O
when	O
hosting	O
valuable	O
or	O
proprietary	O
information	O
.	O
</s>
