<s>
UPower	B-Application
(	O
previously	O
DeviceKit-power	B-Application
)	O
is	O
a	O
piece	O
of	O
middleware	B-General_Concept
(	O
an	O
abstraction	O
layer	O
)	O
for	O
power	O
management	O
on	O
Linux	B-Application
systems	O
.	O
</s>
<s>
It	O
consists	O
of	O
a	O
daemon	B-Operating_System
(	O
upowerd	B-Application
)	O
,	O
an	O
application	B-Application
programming	I-Application
interface	I-Application
and	O
a	O
set	O
of	O
command	B-Application
line	I-Application
tools	I-Application
.	O
</s>
<s>
The	O
daemon	B-Operating_System
provides	O
its	O
functionality	O
to	O
applications	O
over	O
the	O
system	O
bus	O
(	O
an	O
instance	O
of	O
D-Bus	B-Language
,	O
service	O
org.freedesktop.UPower	O
)	O
.	O
</s>
<s>
PolicyKit	B-Language
restricts	O
access	O
to	O
the	O
UPower	B-Application
functionality	O
for	O
initiating	O
hibernate	O
mode	O
or	O
shutting	O
down	O
the	O
operating	O
system	O
(	O
freedesktop.upower.policy	O
)	O
.	O
</s>
<s>
The	O
command-line	B-Application
client	O
program	O
upower	B-Application
can	O
be	O
used	O
to	O
query	O
and	O
monitor	O
information	O
about	O
the	O
power	O
supply	O
devices	O
in	O
the	O
system	O
.	O
</s>
<s>
Graphical	B-Application
user	I-Application
interfaces	I-Application
to	O
the	O
functionality	O
of	O
UPower	B-Application
include	O
the	O
GNOME	B-Application
Power	O
Manager	O
and	O
the	O
Xfce	B-Language
Power	O
Manager	O
.	O
</s>
<s>
UPower	B-Application
is	O
a	O
product	O
of	O
the	O
cross-desktop	O
freedesktop.org	B-Application
project	O
.	O
</s>
<s>
As	O
free	B-Application
software	I-Application
it	O
is	O
published	O
with	O
its	O
source	O
code	O
under	O
the	O
terms	O
of	O
version	O
2	O
or	O
later	O
of	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
was	O
conceived	O
as	O
a	O
replacement	O
for	O
the	O
corresponding	O
features	O
of	O
the	O
deprecated	O
HAL	B-Application
.	O
</s>
<s>
In	O
2008	O
,	O
David	O
Zeuthen	O
started	O
a	O
comprehensive	O
rewrite	O
of	O
HAL	B-Application
.	O
</s>
<s>
This	O
resulted	O
in	O
a	O
set	O
of	O
separate	O
services	O
under	O
the	O
new	O
name	O
"	O
DeviceKit	B-Application
"	O
.	O
</s>
<s>
In	O
2010	O
the	O
included	O
DeviceKit-power	B-Application
was	O
renamed	O
.	O
</s>
<s>
UPower	B-Application
was	O
first	O
introduced	O
and	O
established	O
as	O
a	O
standard	O
in	O
GNOME	B-Application
.	O
</s>
<s>
In	O
January	O
2011	O
the	O
desktop	O
environment	O
Xfce	B-Language
followed	O
(	O
version	O
4.8	O
)	O
.	O
</s>
