<s>
The	O
Simple	B-Operating_System
API	I-Operating_System
for	I-Operating_System
Grid	I-Operating_System
Applications	I-Operating_System
(	O
SAGA	B-Operating_System
)	O
is	O
a	O
family	O
of	O
related	O
standards	O
specified	O
by	O
the	O
Open	O
Grid	O
Forum	O
to	O
define	O
an	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-General_Concept
)	O
for	O
common	O
distributed	B-Architecture
computing	I-Architecture
functionality	O
.	O
</s>
<s>
The	O
SAGA	B-Operating_System
specification	O
for	O
distributed	B-Architecture
computing	I-Architecture
originally	O
consisted	O
of	O
a	O
single	O
document	O
,	O
GFD.90	O
,	O
which	O
was	O
released	O
in	O
2009	O
.	O
</s>
<s>
The	O
SAGA	B-Operating_System
API	B-General_Concept
does	O
not	O
strive	O
to	O
replace	O
Globus	O
or	O
similar	O
grid	B-Architecture
computing	I-Architecture
middleware	B-General_Concept
systems	O
,	O
and	O
does	O
not	O
target	O
middleware	B-General_Concept
developers	O
,	O
but	O
application	O
developers	O
with	O
no	O
background	O
on	O
grid	B-Architecture
computing	I-Architecture
.	O
</s>
<s>
The	O
API	B-General_Concept
insulates	O
application	O
developers	O
from	O
middleware	B-General_Concept
.	O
</s>
<s>
The	O
specification	O
of	O
services	O
,	O
and	O
the	O
protocols	O
to	O
interact	O
with	O
them	O
,	O
is	O
out	O
of	O
the	O
scope	O
of	O
SAGA	B-Operating_System
.	O
</s>
<s>
Rather	O
,	O
the	O
API	B-General_Concept
seeks	O
to	O
hide	O
the	O
detail	O
of	O
any	O
service	O
infrastructures	O
that	O
may	O
or	O
may	O
not	O
be	O
used	O
to	O
implement	O
the	O
functionality	O
that	O
the	O
application	O
developer	O
needs	O
.	O
</s>
<s>
The	O
API	B-General_Concept
aligns	O
,	O
however	O
,	O
with	O
all	O
middleware	B-General_Concept
standards	O
within	O
Open	O
Grid	O
Forum	O
(	O
OGF	O
)	O
.	O
</s>
<s>
The	O
SAGA	B-Operating_System
API	B-General_Concept
defined	O
a	O
mechanism	O
to	O
specify	O
additional	O
API	B-General_Concept
packages	O
which	O
expand	O
its	O
scope	O
.	O
</s>
<s>
The	O
SAGA	B-Operating_System
Core	O
API	B-General_Concept
itself	O
defines	O
a	O
number	O
of	O
packages	O
:	O
job	O
management	O
,	O
file	O
management	O
,	O
replica	B-Architecture
management	O
,	O
remote	B-Operating_System
procedure	I-Operating_System
calls	I-Operating_System
,	O
and	O
streams	O
.	O
</s>
<s>
SAGA	B-Operating_System
covers	O
the	O
most	O
important	O
and	O
frequently	O
used	O
distributed	O
functionality	O
and	O
is	O
supported	O
and	O
available	O
on	O
every	O
major	O
grid	O
systems	O
-	O
Extreme	O
Science	O
and	O
Engineering	O
Discovery	O
Environment	O
(	O
XSEDE	O
)	O
,	O
EGI	O
and	O
FutureGrid	O
.	O
</s>
<s>
SAGA	B-Operating_System
not	O
only	O
supports	O
a	O
wide	O
range	O
of	O
distributed	B-Architecture
programming	I-Architecture
and	O
coordination	O
models	O
but	O
is	O
also	O
easily	O
extensible	O
to	O
support	O
new	O
and	O
emerging	O
middleware	B-General_Concept
.	O
</s>
<s>
The	O
SAGA	B-Operating_System
API	B-General_Concept
is	O
standardised	O
in	O
the	O
SAGA	B-Operating_System
Working	O
Group	O
the	O
Open	O
Grid	O
Forum	O
.	O
</s>
<s>
the	O
SAGA	B-Operating_System
Core	O
API	B-General_Concept
specification	O
defines	O
a	O
set	O
of	O
general	O
API	B-General_Concept
principles	O
(	O
the	O
'	O
SAGA	B-Operating_System
Look	O
and	O
Feel	O
 '	O
,	O
and	O
a	O
set	O
of	O
API	B-General_Concept
packages	O
which	O
render	O
commonly	O
used	O
Grid	O
programming	O
patterns	O
(	O
job	O
management	O
,	O
file	O
management	O
and	O
access	O
,	O
replica	B-Architecture
management	O
etc	O
.	O
)	O
</s>
<s>
The	O
SAGA	B-Operating_System
Core	O
specification	O
also	O
defines	O
how	O
additional	O
API	B-General_Concept
packages	O
are	O
to	O
be	O
defined	O
,	O
and	O
how	O
they	O
relate	O
to	O
the	O
Core	O
API	B-General_Concept
,	O
and	O
to	O
its	O
'	O
Look	O
and	O
Feel	O
 '	O
.	O
</s>
<s>
Based	O
on	O
that	O
,	O
a	O
number	O
of	O
API	B-General_Concept
extensions	O
have	O
been	O
defined	O
,	O
and	O
are	O
in	O
various	O
states	O
of	O
the	O
standardisation	O
process	O
.	O
</s>
<s>
All	O
SAGA	B-Operating_System
specifications	O
are	O
defined	O
in	O
(	O
a	O
flavor	O
of	O
)	O
IDL	B-General_Concept
,	O
and	O
thus	O
object	B-Language
oriented	I-Language
,	O
but	O
language	O
neutral	O
.	O
</s>
<s>
Different	O
language	O
bindings	O
exist	O
(	O
Java	B-Language
,	O
C++	B-Language
,	O
Python	B-Language
)	O
,	O
but	O
are	O
,	O
at	O
this	O
point	O
,	O
not	O
standardised	O
.	O
</s>
<s>
Nevertheless	O
,	O
different	O
implementations	O
of	O
these	O
language	O
bindings	O
have	O
a	O
relatively	O
coherent	O
API	B-General_Concept
definition	O
(	O
in	O
particular	O
,	O
the	O
different	O
Java	B-Language
implementations	O
share	O
the	O
same	O
abstract	O
API	B-General_Concept
classes	O
)	O
.	O
</s>
<s>
The	O
'	O
Look	O
and	O
Feel	O
 '	O
part	O
of	O
the	O
SAGA	B-Operating_System
Core	O
API	B-General_Concept
specification	O
covers	O
the	O
following	O
areas	O
:	O
</s>
<s>
SAGA	B-Operating_System
is	O
designed	O
as	O
an	O
object	B-Language
oriented	I-Language
interface	O
.	O
</s>
<s>
It	O
encapsulates	O
related	O
functionality	O
in	O
a	O
set	O
of	O
objects	O
,	O
that	O
are	O
grouped	O
in	O
functional	O
namespaces	O
,	O
which	O
are	O
called	O
packages	O
in	O
SAGA	B-Operating_System
.	O
</s>
<s>
The	O
SAGA	B-Operating_System
core	O
implementation	O
defines	O
the	O
following	O
packages	O
:	O
</s>
<s>
The	O
overall	O
architecture	O
of	O
SAGA	B-Operating_System
follows	O
the	O
adaptor	O
pattern	O
,	O
a	O
software	O
design	O
pattern	O
which	O
is	O
used	O
for	O
translating	O
one	O
interface	O
into	O
another	O
.	O
</s>
<s>
In	O
SAGA	B-Operating_System
it	O
translates	O
the	O
calls	O
from	O
the	O
API	B-General_Concept
packages	O
to	O
the	O
interfaces	O
of	O
the	O
underlying	O
middleware	B-General_Concept
.	O
</s>
<s>
The	O
SAGA	B-Operating_System
run-time	B-Device
system	I-Device
uses	O
late	O
binding	O
to	O
decide	O
at	O
run-time	B-Application
which	O
plug-in	B-Application
(	O
middleware	B-General_Concept
adaptor	O
)	O
to	O
load	O
and	O
bind	O
.	O
</s>
<s>
The	O
following	O
table	O
lists	O
the	O
distributed	O
middleware	B-General_Concept
systems	O
that	O
are	O
currently	O
supported	O
by	O
SAGA	B-Operating_System
.	O
</s>
<s>
The	O
column	O
labeled	O
Adaptor	O
Suite	O
names	O
the	O
collection	O
(	O
release	O
package	O
)	O
of	O
the	O
(	O
set	O
of	O
)	O
middleware	B-General_Concept
adaptors	O
that	O
provides	O
support	O
for	O
the	O
middleware	B-General_Concept
system	O
.	O
</s>
<s>
Since	O
the	O
SAGA	B-Operating_System
interface	O
definitions	O
are	O
not	O
bound	O
to	O
any	O
specific	O
programming	O
language	O
,	O
several	O
implementations	O
of	O
the	O
SAGA	B-Operating_System
standards	O
exist	O
in	O
different	O
programming	O
languages	O
.	O
</s>
<s>
Apart	O
from	O
the	O
implementation	O
language	O
,	O
they	O
differ	O
from	O
each	O
other	O
in	O
their	O
completeness	O
in	O
terms	O
of	O
standard	O
coverage	O
,	O
as	O
well	O
as	O
in	O
their	O
support	O
for	O
distributed	O
middleware	B-General_Concept
.	O
</s>
<s>
was	O
the	O
first	O
complete	O
implementation	O
of	O
the	O
SAGA	B-Operating_System
Core	O
specification	O
,	O
written	O
in	O
C++	B-Language
.	O
</s>
<s>
Currently	O
the	O
C++	B-Language
implementation	O
is	O
not	O
under	O
active	O
development	O
.	O
</s>
<s>
is	O
a	O
light-weight	O
Python	B-Language
package	O
that	O
implements	O
parts	O
of	O
the	O
interface	O
specification	O
and	O
provides	O
plug-ins	B-Application
for	O
different	O
distributed	O
middleware	B-General_Concept
systems	O
and	O
services	O
.	O
</s>
<s>
RADICAL-SAGA	O
implements	O
the	O
most	O
commonly	O
used	O
features	O
of	O
GFD.90	O
based	O
upon	O
extensive	O
use-case	O
analysis	O
,	O
and	O
focuses	O
on	O
usability	O
and	O
simple	O
deployment	O
in	O
real-world	O
heterogeneous	O
distributed	B-Architecture
computing	I-Architecture
environments	O
and	O
application	O
scenarios	O
.	O
</s>
<s>
RADICAL-SAGA	O
currently	O
implements	O
the	O
job	O
and	O
the	O
file	O
management	O
core	O
APIs	B-General_Concept
as	O
well	O
as	O
the	O
resource	O
management	O
API	B-General_Concept
extension	O
.	O
</s>
<s>
RADICAL-SAGA	O
provides	O
plug-ins	B-Application
for	O
different	O
distributed	O
middleware	B-General_Concept
systems	O
and	O
services	O
,	O
including	O
support	O
for	O
the	O
PBS	B-Application
,	O
Sun	B-Operating_System
Grid	I-Operating_System
Engine	I-Operating_System
,	O
SSH	B-Protocol
,	O
SFTP	B-Protocol
and	O
others	O
.	O
</s>
<s>
RADICAL-SAGA	O
can	O
be	O
used	O
to	O
develop	O
distributed	B-Architecture
applications	I-Architecture
and	O
frameworks	O
that	O
run	O
on	O
distributed	O
cyber-infrastructure	O
including	O
,	O
LONI	O
and	O
,	O
other	O
clouds	O
and	O
local	O
clusters	O
.	O
</s>
<s>
JavaSAGA	O
is	O
a	O
Java	B-Language
implementation	O
of	O
SAGA	B-Operating_System
.	O
</s>
<s>
is	O
another	O
Java	B-Language
implementation	O
of	O
the	O
SAGA	B-Operating_System
Core	O
specification	O
.	O
</s>
<s>
DESHL	O
is	O
implemented	O
as	O
a	O
set	O
of	O
command-line	O
tools	O
on-top	O
of	O
a	O
SAGA-inspired	O
API	B-General_Concept
implemented	O
in	O
Java	B-Language
.	O
</s>
<s>
On	O
the	O
back-end	O
,	O
it	O
interfaces	O
with	O
HiLA	O
,	O
a	O
generic	O
grid	O
access	O
client	O
library	B-Library
,	O
which	O
is	O
part	O
of	O
the	O
UNICORE	B-General_Concept
system	O
.	O
</s>
<s>
A	O
typical	O
task	O
in	O
a	O
distributed	B-Architecture
application	I-Architecture
is	O
to	O
submit	O
a	O
job	O
to	O
a	O
local	O
or	O
remote	O
distributed	B-General_Concept
resource	I-General_Concept
manager	I-General_Concept
.	O
</s>
<s>
SAGA	B-Operating_System
provides	O
a	O
high-level	O
API	B-General_Concept
called	O
the	O
job	O
package	O
for	O
this	O
.	O
</s>
<s>
The	O
following	O
two	O
simple	O
examples	O
show	O
how	O
the	O
SAGA	B-Operating_System
job	O
package	O
API	B-General_Concept
can	O
be	O
used	O
to	O
submit	O
a	O
Message	B-Application
Passing	I-Application
Interface	I-Application
(	O
MPI	O
)	O
job	O
to	O
a	O
remote	O
Globus	O
GRAM	B-Operating_System
resource	O
manager	O
.	O
</s>
<s>
The	O
work	O
related	O
to	O
the	O
SAGA	B-Operating_System
Project	O
is	O
funded	O
by	O
the	O
following	O
grants	O
:	O
,	O
,	O
.	O
</s>
