<s>
Ext3cow	B-Application
or	O
third	B-Application
extended	I-Application
filesystem	I-Application
with	O
copy-on-write	B-Language
is	O
an	O
open	B-License
source	I-License
,	O
versioning	B-Application
file	I-Application
system	I-Application
based	O
on	O
the	O
ext3	B-Application
file	O
system	O
.	O
</s>
<s>
Versioning	O
is	O
implemented	O
through	O
block-level	O
copy-on-write	B-Language
.	O
</s>
<s>
It	O
shares	O
many	O
of	O
its	O
performance	O
characteristics	O
with	O
ext3	B-Application
.	O
</s>
<s>
Ext3cow	B-Application
provides	O
a	O
time-shifting	O
interface	O
that	O
permits	O
a	O
real-time	O
and	O
continuous	O
view	O
of	O
data	O
in	O
the	O
past	O
.	O
</s>
<s>
Time-shifting	O
is	O
a	O
novel	O
interface	O
,	O
introduced	O
in	O
ext3cow	B-Application
,	O
allowing	O
users	O
to	O
navigate	O
through	O
and	O
access	O
past	O
namespaces	O
by	O
adding	O
a	O
time	O
component	O
to	O
their	O
commands	O
.	O
</s>
<s>
A	O
version	O
of	O
ext3cow	B-Application
for	O
the	O
Linux	B-Application
2.6	O
kernel	O
was	O
released	O
on	O
March	O
30	O
,	O
2007	O
.	O
</s>
<s>
Details	O
on	O
ext3cow	B-Application
's	O
implementation	O
can	O
be	O
found	O
in	O
a	O
2005	O
paper	O
.	O
</s>
