<s>
A	O
tuple	B-Operating_System
space	I-Operating_System
is	O
an	O
implementation	O
of	O
the	O
associative	B-Data_Structure
memory	I-Data_Structure
paradigm	O
for	O
parallel/distributed	O
computing	O
.	O
</s>
<s>
It	O
provides	O
a	O
repository	O
of	O
tuples	B-Application
that	O
can	O
be	O
accessed	O
concurrently	O
.	O
</s>
<s>
Producers	O
post	O
their	O
data	O
as	O
tuples	B-Application
in	O
the	O
space	O
,	O
and	O
the	O
consumers	O
then	O
retrieve	O
data	O
from	O
the	O
space	O
that	O
match	O
a	O
certain	O
pattern	O
.	O
</s>
<s>
Tuple	B-Operating_System
space	I-Operating_System
may	O
be	O
thought	O
as	O
a	O
form	O
of	O
distributed	B-Operating_System
shared	I-Operating_System
memory	I-Operating_System
.	O
</s>
<s>
Tuple	B-Operating_System
spaces	I-Operating_System
were	O
the	O
theoretical	O
underpinning	O
of	O
the	O
Linda	B-Language
language	O
developed	O
by	O
David	O
Gelernter	O
and	O
Nicholas	O
Carriero	O
at	O
Yale	O
University	O
in	O
1986	O
.	O
</s>
<s>
Implementations	O
of	O
tuple	B-Operating_System
spaces	I-Operating_System
have	O
also	O
been	O
developed	O
for	O
Java	B-Device
(	O
JavaSpaces	B-Operating_System
)	O
,	O
Lisp	B-Language
,	O
Lua	B-Language
,	O
Prolog	B-Language
,	O
Python	B-Language
,	O
Ruby	B-Language
,	O
Smalltalk	B-Application
,	O
Tcl	B-Operating_System
,	O
and	O
the	O
.NET	B-Application
Framework	I-Application
.	O
</s>
<s>
Object	B-Operating_System
Spaces	I-Operating_System
is	O
a	O
paradigm	O
for	O
development	O
of	O
distributed	B-Architecture
computing	I-Architecture
applications	O
.	O
</s>
<s>
It	O
is	O
characterized	O
by	O
the	O
existence	O
of	O
logical	O
entities	O
,	O
called	O
Object	B-Operating_System
Spaces	I-Operating_System
.	O
</s>
<s>
All	O
the	O
participants	O
of	O
the	O
distributed	O
application	O
share	O
an	O
Object	B-Operating_System
Space	I-Operating_System
.	O
</s>
<s>
A	O
provider	O
of	O
a	O
service	O
encapsulates	O
the	O
service	O
as	O
an	O
Object	B-Language
,	O
and	O
puts	O
it	O
in	O
the	O
Object	B-Operating_System
Space	I-Operating_System
.	O
</s>
<s>
Clients	O
of	O
a	O
service	O
then	O
access	O
the	O
Object	B-Operating_System
Space	I-Operating_System
,	O
find	O
out	O
which	O
object	B-Language
provides	O
the	O
needed	O
service	O
,	O
and	O
have	O
the	O
request	O
serviced	O
by	O
the	O
object	B-Language
.	O
</s>
<s>
Object	B-Operating_System
Spaces	I-Operating_System
,	O
as	O
a	O
computing	O
paradigm	O
,	O
was	O
put	O
forward	O
in	O
the	O
1980s	O
by	O
David	O
Gelernter	O
at	O
Yale	O
University	O
.	O
</s>
<s>
Gelernter	O
developed	O
a	O
language	O
called	O
Linda	B-Language
to	O
support	O
the	O
concept	O
of	O
global	O
object	B-Language
coordination	O
.	O
</s>
<s>
Object	B-Operating_System
Space	I-Operating_System
can	O
be	O
thought	O
of	O
as	O
a	O
virtual	O
repository	O
,	O
shared	O
amongst	O
providers	O
and	O
accessors	O
of	O
network	O
services	O
,	O
which	O
are	O
themselves	O
abstracted	O
as	O
objects	O
.	O
</s>
<s>
An	O
object	B-Language
,	O
when	O
deposited	O
into	O
a	O
space	O
,	O
needs	O
to	O
be	O
registered	O
with	O
an	O
Object	B-Language
Directory	O
in	O
the	O
Object	B-Operating_System
Space	I-Operating_System
.	O
</s>
<s>
Any	O
processes	O
can	O
then	O
identify	O
the	O
object	B-Language
from	O
the	O
Object	B-Language
Directory	O
,	O
using	O
properties	O
lookup	O
,	O
where	O
the	O
property	O
specifying	O
the	O
criteria	O
for	O
the	O
lookup	O
of	O
the	O
object	B-Language
is	O
its	O
name	O
or	O
some	O
other	O
property	O
which	O
uniquely	O
identifies	O
it	O
.	O
</s>
<s>
A	O
process	O
may	O
choose	O
to	O
wait	O
for	O
an	O
object	B-Language
to	O
be	O
placed	O
in	O
the	O
Object	B-Operating_System
Space	I-Operating_System
,	O
if	O
the	O
needed	O
object	B-Language
is	O
not	O
already	O
present	O
.	O
</s>
<s>
Objects	O
,	O
when	O
deposited	O
in	O
an	O
Object	B-Operating_System
Space	I-Operating_System
are	O
passive	O
,	O
i.e.	O
,	O
their	O
methods	O
cannot	O
be	O
invoked	O
while	O
the	O
objects	O
are	O
in	O
the	O
Object	B-Operating_System
Space	I-Operating_System
.	O
</s>
<s>
Instead	O
,	O
the	O
accessing	O
process	O
must	O
retrieve	O
it	O
from	O
the	O
Object	B-Operating_System
Space	I-Operating_System
into	O
its	O
local	O
memory	O
,	O
use	O
the	O
service	O
provided	O
by	O
the	O
object	B-Language
,	O
update	O
the	O
state	O
of	O
the	O
object	B-Language
and	O
place	O
it	O
back	O
into	O
the	O
Object	B-Operating_System
Space	I-Operating_System
.	O
</s>
<s>
This	O
paradigm	O
inherently	O
provides	O
mutual	B-Operating_System
exclusion	I-Operating_System
.	O
</s>
<s>
Because	O
once	O
an	O
object	B-Language
is	O
accessed	O
,	O
it	O
has	O
to	O
be	O
removed	O
from	O
the	O
Object	B-Operating_System
Space	I-Operating_System
,	O
and	O
is	O
placed	O
back	O
only	O
after	O
it	O
has	O
been	O
released	O
.	O
</s>
<s>
This	O
means	O
that	O
no	O
other	O
process	O
can	O
access	O
an	O
object	B-Language
while	O
it	O
is	O
being	O
used	O
by	O
one	O
process	O
,	O
thereby	O
ensuring	O
mutual	B-Operating_System
exclusion	I-Operating_System
.	O
</s>
<s>
JavaSpaces	B-Operating_System
is	O
a	O
service	O
specification	O
providing	O
a	O
distributed	O
object	B-Language
exchange	O
and	O
coordination	O
mechanism	O
(	O
which	O
may	O
or	O
may	O
not	O
be	O
persistent	O
)	O
for	O
Java	B-Device
objects	O
.	O
</s>
<s>
It	O
is	O
used	O
to	O
store	O
the	O
distributed	B-Architecture
system	I-Architecture
state	O
and	O
implement	O
distributed	B-Operating_System
algorithms	I-Operating_System
.	O
</s>
<s>
In	O
a	O
JavaSpace	B-Operating_System
,	O
all	O
communication	O
partners	O
(	O
peers	O
)	O
communicate	O
and	O
coordinate	O
by	O
sharing	O
state	O
.	O
</s>
<s>
JavaSpaces	B-Operating_System
can	O
be	O
used	O
to	O
achieve	O
scalability	B-Architecture
through	O
parallel	O
processing	O
,	O
it	O
can	O
also	O
be	O
used	O
to	O
provide	O
reliable	O
storage	O
of	O
objects	O
through	O
distributed	O
replication	O
,	O
although	O
this	O
wo	O
n't	O
survive	O
a	O
total	O
power	O
failure	O
like	O
a	O
disk	O
;	O
it	O
is	O
regarded	O
by	O
many	O
to	O
be	O
reliable	O
as	O
long	O
as	O
the	O
power	O
is	O
reliable	O
.	O
</s>
<s>
Distribution	O
can	O
also	O
be	O
to	O
remote	O
locations	O
;	O
however	O
,	O
this	O
is	O
rare	O
as	O
JavaSpaces	B-Operating_System
are	O
usually	O
used	O
for	O
low-latency	O
,	O
high-performance	O
applications	O
rather	O
than	O
reliable	O
object	B-Language
caching	O
.	O
</s>
<s>
The	O
most	O
common	O
software	O
pattern	O
used	O
in	O
JavaSpaces	B-Operating_System
is	O
the	O
Master-Worker	O
pattern	O
.	O
</s>
<s>
JavaSpaces	B-Operating_System
is	O
part	O
of	O
the	O
Java	B-Device
Jini	B-Language
technology	O
,	O
which	O
on	O
its	O
own	O
has	O
not	O
been	O
a	O
commercial	O
success	O
.	O
</s>
<s>
The	O
technology	O
has	O
found	O
and	O
kept	O
new	O
users	O
over	O
the	O
years	O
and	O
some	O
vendors	O
are	O
offering	O
JavaSpaces-based	O
products	O
.	O
</s>
<s>
JavaSpaces	B-Operating_System
remains	O
a	O
niche	O
technology	O
mostly	O
used	O
in	O
the	O
financial	O
services	O
and	O
telco	O
industries	O
where	O
it	O
continues	O
to	O
maintain	O
a	O
faithful	O
following	O
.	O
</s>
<s>
The	O
announcement	O
of	O
Jini/JavaSpaces	O
created	O
quite	O
some	O
hype	O
although	O
Sun	O
co-founder	O
and	O
chief	O
Jini	B-Language
architect	O
Bill	O
Joy	O
put	O
it	O
straight	O
that	O
this	O
distributed	B-Architecture
systems	I-Architecture
dream	O
will	O
take	O
"	O
a	O
quantum	O
leap	O
in	O
thinking	O
"	O
.	O
</s>
<s>
The	O
following	O
example	O
shows	O
an	O
application	O
made	O
using	O
JavaSpaces	B-Operating_System
.	O
</s>
<s>
First	O
,	O
an	O
object	B-Language
to	O
be	O
shared	O
in	O
the	O
Object	B-Operating_System
Space	I-Operating_System
is	O
made	O
.	O
</s>
<s>
Such	O
an	O
object	B-Language
is	O
called	O
an	O
Entry	O
in	O
JavaSpace	B-Operating_System
terminology	O
.	O
</s>
<s>
The	O
server	O
which	O
provides	O
this	O
service	O
will	O
create	O
an	O
Object	B-Operating_System
Space	I-Operating_System
,	O
or	O
JavaSpace	B-Operating_System
.	O
</s>
<s>
The	O
Entry	O
is	O
then	O
written	O
into	O
the	O
JavaSpace	B-Operating_System
.	O
</s>
<s>
The	O
client	O
reads	O
the	O
entry	O
from	O
the	O
JavaSpace	B-Operating_System
and	O
invokes	O
its	O
method	O
to	O
access	O
the	O
service	O
,	O
updating	O
its	O
usage	O
count	O
by	O
doing	O
so	O
.	O
</s>
<s>
The	O
updated	O
Entry	O
is	O
written	O
back	O
to	O
the	O
JavaSpace	B-Operating_System
.	O
</s>
<s>
Eric	O
Freeman	O
,	O
Susanne	O
Hupfer	O
,	O
Ken	O
Arnold	O
:	O
JavaSpaces	B-Operating_System
Principles	O
,	O
Patterns	O
,	O
and	O
Practice	O
.	O
</s>
<s>
Phil	O
Bishop	O
,	O
Nigel	O
Warren	O
:	O
JavaSpaces	B-Operating_System
in	O
Practice	O
.	O
</s>
<s>
Max	O
K	O
.	O
Goff	O
:	O
Network	O
Distributed	B-Architecture
Computing	I-Architecture
:	O
Fitscapes	O
and	O
Fallacies	O
,	O
2004	O
,	O
Prentice	O
Hall	O
,	O
</s>
<s>
:	O
Professional	O
Java	B-Device
Server	O
Programming	O
,	O
1999	O
,	O
Wrox	O
Press	O
,	O
</s>
<s>
Steven	O
Halter	O
:	O
JavaSpaces	B-Operating_System
Example	O
by	O
Example	O
,	O
2002	O
,	O
Prentice	O
Hall	O
PTR	O
,	O
</s>
