<s>
SCOOP	B-Application
(	O
Simple	O
Concurrent	O
Object	O
Oriented	O
Programming	O
)	O
is	O
a	O
concurrency	O
model	O
designed	O
for	O
the	O
Eiffel	B-Language
programming	I-Language
language	I-Language
,	O
conceived	O
by	O
Eiffel	B-Language
's	O
creator	O
and	O
designer	O
,	O
Bertrand	O
Meyer	O
.	O
</s>
<s>
SCOOP	B-Application
defines	O
a	O
way	O
for	O
an	O
object	O
oriented	O
program	O
to	O
be	O
written	O
without	O
the	O
concept	O
of	O
threads	B-Operating_System
,	O
locks	O
,	O
or	O
other	O
typical	O
multiprogramming	O
methods	O
.	O
</s>
<s>
A	O
prototype	O
implementation	O
was	O
developed	O
in	O
1995	O
by	O
Eiffel	B-Language
Software	O
.	O
</s>
<s>
An	O
article	O
by	O
Compton	O
and	O
Walker	O
provides	O
an	O
overview	O
of	O
SCOOP	B-Application
and	O
describes	O
another	O
early	O
implementation	O
.	O
</s>
<s>
Work	O
on	O
SCOOP	B-Application
proceeded	O
at	O
the	O
Chair	O
of	O
Software	O
Engineering	O
at	O
ETH	O
Zurich	O
.	O
</s>
<s>
SCOOP	B-Application
became	O
available	O
as	O
a	O
standard	O
part	O
of	O
EiffelStudio	B-Application
early	O
in	O
2011	O
.	O
</s>
<s>
SCOOP	B-Application
works	O
by	O
allowing	O
references	O
to	O
certain	O
objects	O
to	O
be	O
declared	O
as	O
separate	O
.	O
</s>
<s>
In	O
the	O
code	O
below	O
,	O
an	O
entity	O
local_inventory	O
is	O
declared	O
as	O
a	O
separate	O
type	O
,	O
by	O
specifying	O
the	O
Eiffel	B-Language
language	O
keyword	O
separate	O
in	O
the	O
declaration	O
.	O
</s>
<s>
A	O
separate	O
object	O
may	O
be	O
handled	O
by	O
a	O
SCOOP	B-Application
processor	O
that	O
is	O
different	O
from	O
the	O
processor	O
handling	O
the	O
referencing	O
object	O
.	O
</s>
<s>
A	O
SCOOP	B-Application
processor	O
is	O
the	O
abstract	O
notion	O
of	O
an	O
autonomous	O
thread	B-Operating_System
of	O
control	O
that	O
handles	O
the	O
execution	O
of	O
operations	O
on	O
one	O
or	O
more	O
objects	O
.	O
</s>
<s>
SCOOP	B-Application
processors	O
are	O
independent	O
of	O
underlying	O
concurrency	O
mechanisms	O
like	O
processor	B-Operating_System
threads	I-Operating_System
,	O
multiple	B-Architecture
processor	I-Architecture
cores	I-Architecture
,	O
and	O
distributed	B-Architecture
computer	I-Architecture
systems	I-Architecture
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
concept	O
of	O
separateness	O
,	O
SCOOP	B-Application
exploits	O
the	O
principles	O
of	O
design	B-Application
by	I-Application
contract	I-Application
as	O
part	O
of	O
the	O
SCOOP	B-Application
strategy	O
for	O
synchronizing	O
access	O
to	O
shared	O
separate	O
resources	O
.	O
</s>
<s>
In	O
the	O
presence	O
of	O
SCOOP	B-Application
and	O
given	O
the	O
separateness	O
of	O
local_inventory	O
,	O
making	O
the	O
check	O
on	O
has_item	O
before	O
calling	O
item	O
would	O
not	O
be	O
reliable	O
.	O
</s>
<s>
This	O
is	O
because	O
the	O
state	O
of	O
local_inventory	O
could	O
have	O
been	O
changed	O
by	O
requests	O
from	O
other	O
SCOOP	B-Application
processors	O
between	O
the	O
time	O
that	O
the	O
check	O
was	O
made	O
and	O
the	O
time	O
that	O
item	O
could	O
be	O
called	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
when	O
SCOOP	B-Application
is	O
enabled	O
,	O
the	O
precondition	O
has_item	O
is	O
transformed	O
from	O
a	O
correctness	O
condition	O
,	O
which	O
will	O
cause	O
an	O
exception	O
in	O
the	O
case	O
of	O
a	O
violation	O
,	O
to	O
a	O
wait	O
condition	O
.	O
</s>
<s>
In	O
the	O
Eiffel	B-Language
Software	O
implementation	O
,	O
if	O
SCOOP	B-Application
is	O
not	O
enabled	O
,	O
the	O
separate	O
keyword	O
is	O
ignored	O
and	O
sequential	O
processing	O
is	O
assumed	O
.	O
</s>
