<s>
Message-oriented	B-Application
middleware	I-Application
(	O
MOM	O
)	O
is	O
software	O
or	O
hardware	O
infrastructure	O
supporting	O
sending	O
and	O
receiving	O
messages	O
between	O
distributed	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
MOM	O
allows	O
application	B-Architecture
modules	I-Architecture
to	O
be	O
distributed	O
over	O
heterogeneous	O
platforms	O
and	O
reduces	O
the	O
complexity	O
of	O
developing	O
applications	O
that	O
span	O
multiple	O
operating	B-General_Concept
systems	I-General_Concept
and	O
network	O
protocols	O
.	O
</s>
<s>
The	O
middleware	B-General_Concept
creates	O
a	O
distributed	O
communications	O
layer	O
that	O
insulates	O
the	O
application	B-Application
developer	I-Application
from	O
the	O
details	O
of	O
the	O
various	O
operating	B-General_Concept
systems	I-General_Concept
and	O
network	O
interfaces	O
.	O
</s>
<s>
APIs	B-Application
that	O
extend	O
across	O
diverse	O
platforms	O
and	O
networks	O
are	O
typically	O
provided	O
by	O
MOM	O
.	O
</s>
<s>
This	O
middleware	B-General_Concept
layer	O
allows	O
software	O
components	O
(	O
applications	O
,	O
Enterprise	O
JavaBeans	O
,	O
servlets	O
,	O
and	O
other	O
components	O
)	O
that	O
have	O
been	O
developed	O
independently	O
and	O
that	O
run	O
on	O
different	O
networked	O
platforms	O
to	O
interact	O
with	O
one	O
another	O
.	O
</s>
<s>
Applications	O
distributed	O
on	O
different	O
network	O
nodes	O
use	O
the	O
application	B-Application
interface	O
to	O
communicate	O
.	O
</s>
<s>
MOM	O
provides	O
software	O
elements	O
that	O
reside	O
in	O
all	O
communicating	O
components	O
of	O
a	O
client/server	O
architecture	B-Architecture
and	O
typically	O
support	O
asynchronous	O
calls	O
between	O
the	O
client	O
and	O
server	O
applications	O
.	O
</s>
<s>
MOM	O
reduces	O
the	O
involvement	O
of	O
application	B-Application
developers	I-Application
with	O
the	O
complexity	O
of	O
the	O
master-slave	O
nature	O
of	O
the	O
client/server	O
mechanism	O
.	O
</s>
<s>
They	O
are	O
different	O
in	O
that	O
RPC	O
-	O
and	O
ORB-based	O
middleware	B-General_Concept
create	O
systems	O
of	O
tightly	O
coupled	O
components	O
,	O
whereas	O
MOM-based	O
systems	O
allow	O
for	O
a	O
loose	B-Application
coupling	I-Application
of	O
components	O
.	O
</s>
<s>
In	O
these	O
synchronous	O
messaging	O
models	O
,	O
the	O
middleware	B-General_Concept
functions	O
partly	O
as	O
a	O
super-linker	O
,	O
locating	O
the	O
called	O
procedure	O
on	O
a	O
network	O
and	O
using	O
network	O
services	O
to	O
pass	O
function	O
or	O
method	O
parameters	O
to	O
the	O
procedure	O
and	O
then	O
to	O
return	O
results	O
.	O
</s>
<s>
Central	O
reasons	O
for	O
using	O
a	O
message-based	B-Architecture
communications	O
protocol	O
include	O
its	O
ability	O
to	O
store	O
(	O
buffer	O
)	O
,	O
route	O
,	O
or	O
transform	B-General_Concept
messages	O
while	O
conveying	O
them	O
from	O
senders	O
to	O
receivers	O
.	O
</s>
<s>
Using	O
a	O
MOM	O
system	O
,	O
a	O
client	O
makes	O
an	O
API	B-Application
call	O
to	O
send	O
a	O
message	O
to	O
a	O
destination	O
managed	O
by	O
the	O
provider	O
.	O
</s>
<s>
The	O
message-based	B-Architecture
model	O
,	O
coupled	O
with	O
the	O
mediation	O
of	O
the	O
provider	O
,	O
makes	O
it	O
possible	O
to	O
create	O
a	O
system	O
of	O
loosely	B-Application
coupled	I-Application
components	O
.	O
</s>
<s>
MOM	O
comprises	O
a	O
category	O
of	O
inter-application	B-Operating_System
communication	I-Operating_System
software	O
that	O
generally	O
relies	O
on	O
asynchronous	O
message-passing	B-Architecture
,	O
as	O
opposed	O
to	O
a	O
request-response	B-Protocol
architecture	B-Architecture
.	O
</s>
<s>
In	O
asynchronous	O
systems	O
,	O
message	B-Operating_System
queues	I-Operating_System
provide	O
temporary	O
storage	O
when	O
the	O
destination	O
program	O
is	O
busy	O
or	O
not	O
connected	O
.	O
</s>
<s>
In	O
addition	O
,	O
most	O
asynchronous	O
MOM	O
systems	O
provide	O
persistent	B-Application
storage	I-Application
to	O
back	B-Protocol
up	I-Protocol
the	O
message	B-Operating_System
queue	I-Operating_System
.	O
</s>
<s>
This	O
means	O
that	O
the	O
sender	O
and	O
receiver	O
do	O
not	O
need	O
to	O
connect	O
to	O
the	O
network	O
at	O
the	O
same	O
time	O
(	O
asynchronous	B-Operating_System
delivery	I-Operating_System
)	O
,	O
and	O
problems	O
with	O
intermittent	O
connectivity	O
are	O
solved	O
.	O
</s>
<s>
It	O
also	O
means	O
that	O
should	O
the	O
receiver	O
application	B-Application
fail	O
for	O
any	O
reason	O
,	O
the	O
senders	O
can	O
continue	O
unaffected	O
,	O
as	O
the	O
messages	O
they	O
send	O
will	O
simply	O
accumulate	O
in	O
the	O
message	B-Operating_System
queue	I-Operating_System
for	O
later	O
processing	O
when	O
the	O
receiver	O
restarts	O
.	O
</s>
<s>
Many	O
message-oriented	B-Application
middleware	I-Application
implementations	O
depend	O
on	O
a	O
message	B-Operating_System
queue	I-Operating_System
system	O
.	O
</s>
<s>
Some	O
implementations	O
make	O
use	O
of	O
broadcast	B-Operating_System
or	O
multicast	O
distribution	O
paradigms	O
.	O
</s>
<s>
In	O
a	O
message-based	B-Architecture
middleware	B-General_Concept
system	O
,	O
the	O
message	O
received	O
at	O
the	O
destination	O
need	O
not	O
be	O
identical	O
to	O
the	O
message	O
originally	O
sent	O
.	O
</s>
<s>
A	O
MOM	O
system	O
with	O
built-in	O
intelligence	O
can	O
transform	B-General_Concept
messages	O
and	O
route	O
to	O
match	O
the	O
requirements	O
of	O
the	O
sender	O
or	O
of	O
the	O
recipient	O
.	O
</s>
<s>
In	O
conjunction	O
with	O
the	O
routing	O
and	O
broadcast/multicast	O
facilities	O
,	O
one	O
application	B-Application
can	O
send	O
a	O
message	O
in	O
its	O
own	O
native	O
format	O
,	O
and	O
two	O
or	O
more	O
other	O
applications	O
may	O
each	O
receive	O
a	O
copy	O
of	O
the	O
message	O
in	O
their	O
own	O
native	O
format	O
.	O
</s>
<s>
Many	O
modern	O
MOM	O
systems	O
provide	O
sophisticated	O
message	O
transformation	O
(	O
or	O
mapping	O
)	O
tools	O
which	O
allow	O
programmers	B-Application
to	O
specify	O
transformation	O
rules	O
applicable	O
to	O
a	O
simple	O
GUI	B-Application
drag-and-drop	O
operation	O
.	O
</s>
<s>
The	O
primary	O
disadvantage	O
of	O
many	O
message-oriented	B-Application
middleware	I-Application
systems	O
is	O
that	O
they	O
require	O
an	O
extra	O
component	O
in	O
the	O
architecture	B-Architecture
,	O
the	O
message	O
transfer	O
agent	O
(	O
message	B-General_Concept
broker	I-General_Concept
)	O
.	O
</s>
<s>
In	O
addition	O
,	O
many	O
inter-application	B-Operating_System
communications	I-Operating_System
have	O
an	O
intrinsically	O
synchronous	O
aspect	O
,	O
with	O
the	O
sender	O
specifically	O
wanting	O
to	O
wait	O
for	O
a	O
reply	O
to	O
a	O
message	O
before	O
continuing	O
(	O
see	O
real-time	B-General_Concept
computing	I-General_Concept
and	O
near-real-time	B-General_Concept
for	O
extreme	O
cases	O
)	O
.	O
</s>
<s>
Because	O
message-based	B-Architecture
communication	O
inherently	O
functions	O
asynchronously	O
,	O
it	O
may	O
not	O
fit	O
well	O
in	O
such	O
situations	O
.	O
</s>
<s>
With	O
a	O
synchronous	O
messaging	B-Operating_System
system	I-Operating_System
,	O
the	O
calling	O
function	O
does	O
not	O
return	O
until	O
the	O
called	O
function	O
has	O
finished	O
its	O
task	O
.	O
</s>
<s>
In	O
a	O
loosely	B-Application
coupled	I-Application
asynchronous	O
system	O
,	O
the	O
calling	O
client	O
can	O
continue	O
to	O
load	O
work	O
upon	O
the	O
recipient	O
until	O
the	O
resources	O
needed	O
to	O
handle	O
this	O
work	O
are	O
depleted	O
and	O
the	O
called	O
component	O
fails	O
.	O
</s>
<s>
Of	O
course	O
,	O
these	O
conditions	O
can	O
be	O
minimized	O
or	O
avoided	O
by	O
monitoring	O
performance	O
and	O
adjusting	O
message	O
flow	O
,	O
but	O
this	O
is	O
work	O
that	O
is	O
not	O
needed	O
with	O
a	O
synchronous	O
messaging	B-Operating_System
system	I-Operating_System
.	O
</s>
<s>
Historically	O
,	O
there	O
was	O
a	O
lack	O
of	O
standards	O
governing	O
the	O
use	O
of	O
message-oriented	B-Application
middleware	I-Application
that	O
has	O
caused	O
problems	O
.	O
</s>
<s>
Most	O
of	O
the	O
major	O
vendors	O
have	O
their	O
own	O
implementations	O
,	O
each	O
with	O
its	O
own	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
and	O
management	O
tools	O
.	O
</s>
<s>
One	O
of	O
the	O
long-standing	O
standards	O
for	O
message	B-Application
oriented	I-Application
middleware	I-Application
is	O
X/Open	O
group	O
's	O
XATMI	O
specification	O
(	O
Distributed	O
Transaction	O
Processing	O
:	O
The	O
XATMI	O
Specification	O
)	O
which	O
standardizes	O
API	B-Application
for	O
interprocess	B-Operating_System
communications	I-Operating_System
.	O
</s>
<s>
Known	O
implementations	O
for	O
this	O
API	B-Application
is	O
ATR	O
Baltic	O
's	O
Enduro/X	B-Application
middleware	B-General_Concept
and	O
Oracle	B-Application
's	O
Tuxedo	B-Application
.	O
</s>
<s>
The	O
Advanced	B-Operating_System
Message	I-Operating_System
Queuing	I-Operating_System
Protocol	I-Operating_System
(	O
AMQP	B-Operating_System
)	O
is	O
an	O
approved	O
OASIS	O
and	O
ISO	O
standard	O
that	O
defines	O
the	O
protocol	O
and	O
formats	O
used	O
between	O
participating	O
application	B-Application
components	O
,	O
so	O
implementations	O
are	O
interoperable	O
.	O
</s>
<s>
AMQP	B-Operating_System
may	O
be	O
used	O
with	O
flexible	O
routing	O
schemes	O
,	O
including	O
common	O
messaging	B-Operating_System
paradigms	I-Operating_System
like	O
point-to-point	B-Architecture
,	O
fan-out	B-General_Concept
,	O
publish/subscribe	B-Operating_System
,	O
and	O
request-response	B-Protocol
(	O
note	O
that	O
these	O
are	O
intentionally	O
omitted	O
from	O
v1.0	O
of	O
the	O
protocol	O
standard	O
itself	O
,	O
but	O
rely	O
on	O
the	O
particular	O
implementation	O
and/or	O
underlying	O
network	O
protocol	O
for	O
routing	O
)	O
.	O
</s>
<s>
Java	O
applications	O
that	O
use	O
AMQP	B-Operating_System
are	O
typically	O
written	O
in	O
Java	O
JMS	B-Language
.	O
</s>
<s>
Other	O
implementations	O
provide	O
APIs	B-Application
for	O
C#	O
,	O
C++	O
,	O
PHP	O
,	O
Python	O
,	O
Ruby	O
,	O
and	O
other	O
languages	O
.	O
</s>
<s>
The	O
High-Level	B-Operating_System
Architecture	I-Operating_System
(	O
HLA	O
IEEE	B-Operating_System
1516	I-Operating_System
)	O
is	O
an	O
IEEE	O
and	O
SISO	O
standard	O
for	O
simulation	O
interoperability	O
.	O
</s>
<s>
It	O
defines	O
a	O
set	O
of	O
services	O
,	O
provided	O
through	O
an	O
API	B-Application
in	O
C++	O
or	O
Java	O
.	O
</s>
<s>
The	O
services	O
offer	O
publish/subscribe	B-Operating_System
based	O
information	O
exchange	O
,	O
based	O
on	O
a	O
modular	B-Architecture
Federation	O
Object	O
Model	O
.	O
</s>
<s>
The	O
MQ	B-Application
Telemetry	I-Application
Transport	I-Application
(	O
MQTT	B-Application
)	O
is	O
an	O
ISO	O
standard	O
(	O
ISO/IEC	O
PRF	O
20922	O
)	O
supported	O
by	O
the	O
OASIS	O
organization	O
.	O
</s>
<s>
It	O
provides	O
a	O
lightweight	O
publish/subscribe	B-Operating_System
reliable	O
messaging	O
transport	O
protocol	O
on	O
top	O
of	O
TCP/IP	O
suitable	O
for	O
communication	O
in	O
M2M/IoT	O
contexts	O
where	O
a	O
small	O
code	O
footprint	O
is	O
required	O
and/or	O
network	O
bandwidth	O
is	O
at	O
a	O
premium	O
.	O
</s>
<s>
The	O
Object	B-Architecture
Management	I-Architecture
Group	I-Architecture
's	O
Data	B-Application
Distribution	I-Application
Service	I-Application
(	O
DDS	O
)	O
provides	O
message-oriented	O
Publish/Subscribe	B-Operating_System
(	O
P/S	O
)	O
middleware	B-General_Concept
standard	O
that	O
aims	O
to	O
enable	O
scalable	O
,	O
real-time	O
,	O
dependable	O
,	O
high	O
performance	O
and	O
interoperable	O
data	O
exchanges	O
between	O
publishers	O
and	O
subscribers	O
.	O
</s>
<s>
The	O
eXtensible	B-Protocol
Messaging	I-Protocol
and	I-Protocol
Presence	I-Protocol
Protocol	I-Protocol
(	O
XMPP	B-Protocol
)	O
is	O
a	O
communications	O
protocol	O
for	O
message-oriented	B-Application
middleware	I-Application
based	O
on	O
XML	O
(	O
Extensible	O
Markup	O
Language	O
)	O
.	O
</s>
<s>
Designed	O
to	O
be	O
extensible	O
,	O
the	O
protocol	O
has	O
also	O
been	O
used	O
for	O
publish-subscribe	B-Operating_System
systems	O
,	O
signalling	O
for	O
VoIP	O
,	O
video	O
,	O
file	O
transfer	O
,	O
gaming	O
,	O
Internet	O
of	O
Things	O
applications	O
such	O
as	O
the	O
smart	O
grid	O
,	O
and	O
social	O
networking	O
services	O
.	O
</s>
<s>
Unlike	O
most	O
instant	O
messaging	O
protocols	O
,	O
XMPP	B-Protocol
is	O
defined	O
in	O
an	O
open	O
standard	O
and	O
uses	O
an	O
open	O
systems	O
approach	O
of	O
development	O
and	O
application	B-Application
,	O
by	O
which	O
anyone	O
may	O
implement	O
an	O
XMPP	B-Protocol
service	O
and	O
interoperate	O
with	O
other	O
organizations	O
 '	O
implementations	O
.	O
</s>
<s>
Because	O
XMPP	B-Protocol
is	O
an	O
open	O
protocol	O
,	O
implementations	O
can	O
be	O
developed	O
using	O
any	O
software	O
license	O
;	O
although	O
many	O
server	O
,	O
client	O
,	O
and	O
library	O
implementations	O
are	O
distributed	O
as	O
free	O
and	O
open-source	O
software	O
,	O
numerous	O
freeware	O
and	O
proprietary	O
software	O
implementations	O
also	O
exist	O
.	O
</s>
<s>
The	O
Internet	O
Engineering	O
Task	O
Force	O
(	O
IETF	O
)	O
formed	O
an	O
XMPP	B-Protocol
working	O
group	O
in	O
2002	O
to	O
formalize	O
the	O
core	O
protocols	O
as	O
an	O
IETF	O
instant	O
messaging	O
and	O
presence	O
technology	O
.	O
</s>
<s>
The	O
XMPP	B-Protocol
Working	O
group	O
produced	O
four	O
specifications	O
(	O
RFC	O
3920	O
,	O
RFC	O
3921	O
,	O
RFC	O
3922	O
,	O
RFC	O
3923	O
)	O
,	O
which	O
were	O
approved	O
as	O
Proposed	O
Standards	O
in	O
2004	O
.	O
</s>
<s>
In	O
2011	O
,	O
RFC	O
3920	O
and	O
RFC	O
3921	O
were	O
superseded	O
by	O
RFC	O
6120	O
and	O
RFC	O
6121	O
respectively	O
,	O
with	O
RFC	O
6122	O
specifying	O
the	O
XMPP	B-Protocol
address	O
format	O
.	O
</s>
<s>
In	O
addition	O
to	O
these	O
core	O
protocols	O
standardized	O
at	O
the	O
IETF	O
,	O
the	O
XMPP	B-Protocol
Standards	O
Foundation	O
(	O
formerly	O
the	O
Jabber	B-Protocol
Software	O
Foundation	O
)	O
is	O
active	O
in	O
developing	O
open	O
XMPP	B-Protocol
extensions	O
.	O
</s>
<s>
XMPP-based	O
software	O
is	O
deployed	O
widely	O
across	O
the	O
Internet	O
,	O
according	O
to	O
the	O
XMPP	B-Protocol
Standards	O
Foundation	O
,	O
and	O
forms	O
the	O
basis	O
for	O
the	O
Department	O
of	O
Defense	O
(	O
DoD	O
)	O
Unified	O
Capabilities	O
Framework	O
.	O
</s>
<s>
The	O
Java	B-Language
EE	I-Language
programming	O
environment	O
provides	O
a	O
standard	O
API	B-Application
called	O
JMS	B-Language
(	O
Java	B-Language
Message	I-Language
Service	I-Language
)	O
,	O
which	O
is	O
implemented	O
by	O
most	O
MOM	O
vendors	O
and	O
aims	O
to	O
hide	O
the	O
particular	O
MOM	O
API	B-Application
implementations	O
;	O
however	O
,	O
JMS	B-Language
does	O
not	O
define	O
the	O
format	O
of	O
the	O
messages	O
that	O
are	O
exchanged	O
,	O
so	O
JMS	B-Language
systems	O
are	O
not	O
interoperable	O
.	O
</s>
<s>
A	O
similar	O
effort	O
is	O
with	O
the	O
actively	O
evolving	O
OpenMAMA	O
project	O
,	O
which	O
aims	O
to	O
provide	O
a	O
common	O
API	B-Application
,	O
particularly	O
to	O
C	O
clients	O
.	O
</s>
<s>
stock	O
quotes	O
)	O
over	O
pub-sub	O
middleware	B-General_Concept
.	O
</s>
<s>
Message	B-Operating_System
queues	I-Operating_System
allow	O
the	O
exchange	O
of	O
information	O
between	O
distributed	B-Architecture
applications	I-Architecture
.	O
</s>
<s>
A	O
message	B-Operating_System
queue	I-Operating_System
can	O
reside	O
in	O
memory	O
or	O
disk	O
storage	O
.	O
</s>
<s>
Through	O
the	O
message	B-Operating_System
queue	I-Operating_System
,	O
the	O
application	B-Application
can	O
be	O
implemented	O
independently	O
-	O
they	O
do	O
not	O
need	O
to	O
know	O
each	O
other	O
's	O
position	O
,	O
or	O
continue	O
to	O
implement	O
procedures	O
to	O
remove	O
the	O
need	O
for	O
waiting	O
to	O
receive	O
this	O
message	O
.	O
</s>
<s>
Advanced	B-Operating_System
Message	I-Operating_System
Queuing	I-Operating_System
Protocol	I-Operating_System
(	O
AMQP	B-Operating_System
)	O
provides	O
an	O
open	O
standard	O
application	B-Application
layer	O
protocol	O
for	O
message-oriented	B-Application
middleware	I-Application
.	O
</s>
<s>
The	O
Object	B-Architecture
Management	I-Architecture
Group	I-Architecture
's	O
Data	B-Application
Distribution	I-Application
Service	I-Application
(	O
DDS	O
)	O
has	O
added	O
many	O
new	O
standards	O
to	O
the	O
basic	O
DDS	O
specification	O
.	O
</s>
<s>
XMPP	B-Protocol
is	O
a	O
communications	O
protocol	O
for	O
message-oriented	B-Application
middleware	I-Application
based	O
on	O
XML	O
(	O
Extensible	O
Markup	O
Language	O
)	O
.	O
</s>
<s>
Streaming	B-Application
Text	I-Application
Oriented	I-Application
Messaging	I-Application
Protocol	I-Application
(	O
STOMP	O
)	O
,	O
formerly	O
known	O
as	O
TTMP	B-Application
,	O
is	O
a	O
simple	O
text-based	O
protocol	O
,	O
provides	O
an	O
interoperable	O
wire	O
format	O
that	O
allows	O
STOMP	O
clients	O
to	O
talk	O
with	O
any	O
Message	B-General_Concept
Broker	I-General_Concept
supporting	O
the	O
protocol	O
.	O
</s>
<s>
An	O
additional	O
trend	O
sees	O
message-oriented	B-Application
middleware	I-Application
functions	O
being	O
implemented	O
in	O
hardware	O
-	O
usually	O
FPGAs	B-Architecture
or	O
other	O
specialized	O
silicon	O
chips	O
.	O
</s>
