<s>
The	O
Grid	O
and	O
Cloud	O
User	O
Support	O
Environment	O
(	O
gUSE	B-Operating_System
)	O
,	O
also	O
known	O
as	O
WS-PGRADE	O
(	O
Web	O
Service	O
–	O
Parallel	O
Grid	O
Run-time	O
and	O
Application	O
Development	O
Environment	O
)	O
/gUSE	O
,	O
is	O
an	O
open	O
source	O
science	O
gateway	O
framework	O
that	O
enables	O
users	O
to	O
access	O
grid	O
and	O
cloud	O
infrastructures	O
.	O
</s>
<s>
gUSE	B-Operating_System
is	O
developed	O
by	O
the	O
Laboratory	O
of	O
Parallel	O
and	O
Distributed	O
Systems	O
(	O
LPDS	B-Operating_System
)	O
at	O
Institute	O
for	O
Computer	O
Science	O
and	O
Control	O
(	O
SZTAKI	O
)	O
of	O
the	O
Hungarian	O
Academy	O
of	O
Sciences	O
.	O
</s>
<s>
A	O
relevant	O
requirement	O
in	O
the	O
development	O
of	O
gUSE	B-Operating_System
was	O
to	O
enable	O
the	O
simultaneous	O
handling	O
of	O
a	O
very	O
large	O
number	O
of	O
jobs	O
,	O
even	O
in	O
the	O
range	O
of	O
millions	O
,	O
without	O
compromising	O
the	O
response	O
time	O
at	O
the	O
user	O
interface	O
.	O
</s>
<s>
In	O
order	O
to	O
achieve	O
this	O
level	O
of	O
concurrency	O
,	O
the	O
workflow	O
management	O
back-end	O
of	O
gUSE	B-Operating_System
is	O
implemented	O
based	O
on	O
the	O
web	O
service	O
concept	O
of	O
Service	O
Oriented	O
Architecture	O
(	O
SOA	O
)	O
.	O
</s>
<s>
An	O
SG	O
framework	O
,	O
like	O
gUSE	B-Operating_System
,	O
provides	O
a	O
specific	O
set	O
of	O
enabling	O
technologies	O
as	O
well	O
as	O
frontend	O
and	O
backend	O
services	O
that	O
together	O
build	O
a	O
generic	O
gateway	O
.	O
</s>
<s>
An	O
enabling	O
technology	O
such	O
as	O
gUSE	B-Operating_System
provides	O
the	O
required	O
software	O
stack	O
to	O
develop	O
SG	O
frameworks	O
and	O
SG	O
instances	O
(	O
provide	O
a	O
simplified	O
user	O
interface	O
that	O
is	O
highly	O
tailored	O
to	O
the	O
needs	O
of	O
the	O
given	O
scientific	O
community	O
)	O
.	O
</s>
<s>
)	O
,	O
workflow	O
management	O
systems	O
(	O
gUSE	B-Operating_System
itself	O
,	O
MOTEUR	O
,	O
etc	O
.	O
)	O
</s>
<s>
The	O
gUSE	B-Operating_System
SG	O
framework	O
also	O
provides	O
two	O
Application	O
Programming	O
Interfaces	O
(	O
APIs	O
)	O
,	O
namely	O
the	O
Application-Specific	O
Module	O
API	O
and	O
the	O
Remote	O
API	O
,	O
to	O
create	O
application-specific	O
SGs	O
according	O
to	O
the	O
needs	O
of	O
different	O
user	O
communities	O
.	O
</s>
<s>
The	O
gUSE	B-Operating_System
provides	O
with	O
WS-PGRADE	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
to	O
create	O
and	O
execute	O
workflows	O
on	O
various	O
Distributed	O
Computing	O
Infrastructures	O
(	O
DCIs	O
)	O
.	O
</s>
<s>
Among	O
many	O
other	O
features	O
,	O
the	O
main	O
five	O
capabilities	O
of	O
gUSE	B-Operating_System
are	O
as	O
follows	O
:	O
</s>
<s>
(	O
1	O
)	O
gUSE	B-Operating_System
is	O
a	O
general-purpose	O
SG	O
framework	O
under	O
which	O
users	O
can	O
access	O
more	O
than	O
twenty	O
different	O
DCIs	O
via	O
the	O
DCI	O
Bridge	O
service	O
,	O
and	O
six	O
different	O
data	O
storage	O
types	O
(	O
HTTP	O
,	O
HTTPS	O
,	O
GSIFTP	O
,	O
S3	O
,	O
SFTP	O
,	O
and	O
SRM	O
)	O
via	O
the	O
Data	O
Avenue	O
service	O
.	O
</s>
<s>
Both	O
DCI	O
Bridge	O
and	O
Data	O
Avenue	O
were	O
developed	O
as	O
part	O
of	O
the	O
WS-PGRADE/gUSE	O
service	O
stack	O
,	O
but	O
they	O
can	O
also	O
be	O
used	O
as	O
independent	O
services	O
enabling	O
their	O
use	O
from	O
other	O
types	O
of	O
gateways	O
and	O
workflow	O
systems	O
.	O
</s>
<s>
(	O
2	O
)	O
WS-PGRADE/gUSE	O
is	O
a	O
workflow-oriented	O
system	O
.	O
</s>
<s>
Moreover	O
,	O
gUSE	B-Operating_System
extends	O
the	O
concrete	O
workflow	O
concept	O
with	O
the	O
concepts	O
of	O
abstract	O
workflow	O
,	O
workflow	O
instance	O
,	O
and	O
template	O
.	O
</s>
<s>
(	O
3	O
)	O
WS-PGRADE/gUSE	O
supports	O
the	O
development	O
and	O
execution	O
of	O
workflow-based	O
applications	O
.	O
</s>
<s>
Users	O
of	O
gUSE	B-Operating_System
define	O
their	O
applications	O
as	O
workflows	O
.	O
</s>
<s>
(	O
4	O
)	O
gUSE	B-Operating_System
supports	O
the	O
fast	O
development	O
of	O
SG	O
instances	O
by	O
a	O
customization	O
technology	O
.	O
</s>
<s>
gUSE	B-Operating_System
can	O
serve	O
different	O
needs	O
,	O
according	O
to	O
the	O
community	O
requirements	O
about	O
the	O
computational	O
power	O
,	O
the	O
complexity	O
of	O
the	O
applications	O
,	O
and	O
the	O
specificity	O
of	O
the	O
user	O
interface	O
to	O
fit	O
the	O
community	O
needs	O
and	O
to	O
meet	O
its	O
terminology	O
.	O
</s>
<s>
(	O
5	O
)	O
The	O
most	O
important	O
design	O
aspect	O
of	O
gUSE	B-Operating_System
is	O
flexibility	O
.	O
</s>
<s>
in	O
exploiting	O
parallelism	O
:	O
gUSE	B-Operating_System
enables	O
parallel	O
execution	O
inside	O
a	O
workflow	O
node	O
as	O
well	O
as	O
among	O
workflow	O
nodes	O
.	O
</s>
<s>
in	O
the	O
use	O
of	O
DCIs	O
:	O
gUSE	B-Operating_System
can	O
access	O
various	O
DCIs	O
:	O
clusters	O
,	O
cluster	O
grids	O
,	O
desktop	O
grids	O
,	O
supercomputers	O
,	O
and	O
clouds	O
.	O
</s>
<s>
in	O
data	O
storage	O
access	O
:	O
gUSE	B-Operating_System
workflow	O
nodes	O
can	O
access	O
different	O
data	O
storage	O
services	O
in	O
different	O
DCIs	O
via	O
the	O
Data	O
Avenue	O
Blacktop	O
service	O
.	O
</s>
<s>
can	O
be	O
accessed	O
by	O
WS-PGRADE/gUSE	O
either	O
directly	O
(	O
see	O
Chap	O
.	O
</s>
<s>
of	O
supported	O
gateway	O
types	O
:	O
gUSE	B-Operating_System
supports	O
different	O
gateway	O
types	O
:	O
general-purpose	O
gateways	O
for	O
national	O
grids	O
(	O
e.g.	O
,	O
for	O
Greek	O
and	O
Italian	O
NGIs	O
)	O
,	O
general-purpose	O
gateways	O
for	O
particular	O
DCIs	O
(	O
e.g.	O
,	O
EDGI	O
gateway	O
)	O
,	O
general-purpose	O
gateways	O
for	O
specific	O
technologies	O
(	O
e.g.	O
,	O
SHIWA	O
gateway	O
for	O
workflow	O
sharing	O
and	O
interoperation	O
)	O
and	O
domain-specific	O
science	O
gateway	O
instances	O
(	O
e.g.	O
,	O
Swiss	O
proteomics	O
portal	O
,	O
MoSGrid	O
gateway	O
,	O
Autodock	O
gateway	O
,	O
Seizmology	O
gateway	O
,	O
and	O
VisIVO	O
)	O
.	O
</s>
<s>
The	O
main	O
goal	O
of	O
designing	O
the	O
multitier	O
architecture	O
of	O
WS-PGRADE/gUSE	O
was	O
to	O
enable	O
versatile	O
access	O
to	O
many	O
different	O
kinds	O
of	O
DCIs	O
and	O
data	O
storage	O
by	O
different	O
kinds	O
of	O
user	O
interfaces	O
.	O
</s>
<s>
This	O
access	O
can	O
be	O
technically	O
performed	O
through	O
the	O
DCI	O
Bridge	O
job	O
submission	O
service	O
which	O
is	O
in	O
the	O
bottom	O
within	O
the	O
gUSE	B-Operating_System
architectural	O
layers	O
,	O
and	O
via	O
the	O
Data	O
Avenue	O
Blacktop	O
service	O
that	O
is	O
an	O
independent	O
service	O
provided	O
by	O
SZTAKI	O
.	O
</s>
<s>
The	O
middle	O
tier	O
of	O
the	O
gUSE	B-Operating_System
architecture	O
contains	O
the	O
high-level	O
gUSE	B-Operating_System
services	O
.	O
</s>
<s>
These	O
play	O
an	O
important	O
role	O
in	O
the	O
automatic	O
generation	O
of	O
executable	O
workflows	O
in	O
the	O
end-user	O
mode	O
of	O
a	O
WS-PGRADE/gUSE	O
gateway	O
.	O
</s>
<s>
At	O
the	O
top	O
of	O
the	O
three-tier	O
structure	O
,	O
the	O
presentation	O
tier	O
provides	O
WS-PGRADE	O
,	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
of	O
the	O
generic	O
SG	O
framework	O
.	O
</s>
<s>
This	O
layer	O
can	O
be	O
easily	O
customized	O
and	O
extended	O
according	O
to	O
the	O
needs	O
of	O
the	O
SG	O
instances	O
to	O
be	O
derived	O
from	O
gUSE	B-Operating_System
.	O
</s>
<s>
GUSE	B-Operating_System
provides	O
framework	O
for	O
more	O
European	O
SGs	O
:	O
</s>
<s>
gUSE	B-Operating_System
gives	O
one	O
of	O
the	O
underlying	O
workflow	O
development	O
infrastructures	O
to	O
a	O
great	O
number	O
of	O
research	O
activities	O
in	O
numerous	O
EU	O
FP7	O
projects	O
.	O
</s>
<s>
Ongoing	O
EU	O
-	O
and	O
national	O
projects	O
with	O
gUSE	B-Operating_System
:	O
</s>
