<s>
Apache	B-Language
Oozie	I-Language
is	O
a	O
server-based	O
workflow	B-Operating_System
scheduling	O
system	O
to	O
manage	O
Hadoop	B-Application
jobs	O
.	O
</s>
<s>
Workflows	B-Operating_System
in	O
Oozie	B-Language
are	O
defined	O
as	O
a	O
collection	O
of	O
control	O
flow	O
and	O
action	O
nodes	O
in	O
a	O
directed	O
acyclic	O
graph	O
.	O
</s>
<s>
Control	O
flow	O
nodes	O
define	O
the	O
beginning	O
and	O
the	O
end	O
of	O
a	O
workflow	B-Operating_System
(	O
start	O
,	O
end	O
,	O
and	O
failure	O
nodes	O
)	O
as	O
well	O
as	O
a	O
mechanism	O
to	O
control	O
the	O
workflow	B-Operating_System
execution	O
path	O
(	O
decision	O
,	O
fork	O
,	O
and	O
join	O
nodes	O
)	O
.	O
</s>
<s>
Action	O
nodes	O
are	O
the	O
mechanism	O
by	O
which	O
a	O
workflow	B-Operating_System
triggers	O
the	O
execution	O
of	O
a	O
computation/processing	O
task	O
.	O
</s>
<s>
Oozie	B-Language
provides	O
support	O
for	O
different	O
types	O
of	O
actions	O
including	O
Hadoop	B-Application
MapReduce	B-Operating_System
,	O
Hadoop	B-Application
distributed	O
file	O
system	O
operations	O
,	O
Pig	B-Language
,	O
SSH	B-Protocol
,	O
and	O
email	O
.	O
</s>
<s>
Oozie	B-Language
can	O
also	O
be	O
extended	O
to	O
support	O
additional	O
types	O
of	O
actions	O
.	O
</s>
<s>
Oozie	B-Language
workflows	B-Operating_System
can	O
be	O
parameterised	O
using	O
variables	O
such	O
as	O
${inputDir}	O
within	O
the	O
workflow	B-Operating_System
definition	O
.	O
</s>
<s>
When	O
submitting	O
a	O
workflow	B-Operating_System
job	O
,	O
values	O
for	O
the	O
parameters	O
must	O
be	O
provided	O
.	O
</s>
<s>
If	O
properly	O
parameterized	O
(	O
using	O
different	O
output	O
directories	O
)	O
,	O
several	O
identical	O
workflow	B-Operating_System
jobs	O
can	O
run	O
concurrently	O
.	O
</s>
<s>
Oozie	B-Language
is	O
implemented	O
as	O
a	O
Java	B-Language
web	B-Application
application	I-Application
that	O
runs	O
in	O
a	O
Java	B-Application
servlet	I-Application
container	O
and	O
is	O
distributed	O
under	O
the	O
Apache	B-Application
License	I-Application
2.0	I-Application
.	O
</s>
