<s>
Middleware	B-General_Concept
is	O
a	O
type	O
of	O
computer	O
software	O
that	O
provides	O
services	O
to	O
software	O
applications	O
beyond	O
those	O
available	O
from	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Middleware	B-General_Concept
makes	O
it	O
easier	O
for	O
software	B-Application
developers	I-Application
to	O
implement	O
communication	O
and	O
input/output	O
,	O
so	O
they	O
can	O
focus	O
on	O
the	O
specific	O
purpose	O
of	O
their	O
application	O
.	O
</s>
<s>
The	O
term	O
is	O
most	O
commonly	O
used	O
for	O
software	O
that	O
enables	O
communication	O
and	O
management	O
of	O
data	O
in	O
distributed	B-Architecture
applications	I-Architecture
.	O
</s>
<s>
An	O
IETF	O
workshop	O
in	O
2000	O
defined	O
middleware	B-General_Concept
as	O
"	O
those	O
services	O
found	O
above	O
the	O
transport	B-Architecture
(	O
i.e.	O
</s>
<s>
below	O
application-level	O
APIs	B-Application
)	O
.	O
</s>
<s>
In	O
this	O
more	O
specific	O
sense	O
middleware	B-General_Concept
can	O
be	O
described	O
as	O
the	O
dash	O
("-"	O
)	O
in	O
client-server	B-Operating_System
,	O
or	O
the	O
-to	O
-	O
in	O
peer-to-peer	O
.	O
</s>
<s>
Middleware	B-General_Concept
includes	O
web	B-Application
servers	I-Application
,	O
application	B-Application
servers	I-Application
,	O
content	B-Protocol
management	I-Protocol
systems	I-Protocol
,	O
and	O
similar	O
tools	O
that	O
support	O
application	O
development	O
and	O
delivery	O
.	O
</s>
<s>
ObjectWeb	O
defines	O
middleware	B-General_Concept
as	O
:	O
"	O
The	O
software	O
layer	O
that	O
lies	O
between	O
the	O
operating	B-General_Concept
system	I-General_Concept
and	O
applications	O
on	O
each	O
side	O
of	O
a	O
distributed	B-Architecture
computing	I-Architecture
system	O
in	O
a	O
network.	O
"	O
</s>
<s>
Services	O
that	O
can	O
be	O
regarded	O
as	O
middleware	B-General_Concept
include	O
enterprise	B-Architecture
application	I-Architecture
integration	I-Architecture
,	O
data	B-General_Concept
integration	I-General_Concept
,	O
message	B-Application
oriented	I-Application
middleware	I-Application
(	O
MOM	O
)	O
,	O
object	B-General_Concept
request	I-General_Concept
brokers	I-General_Concept
(	O
ORBs	O
)	O
,	O
and	O
the	O
enterprise	B-Application
service	I-Application
bus	I-Application
(	O
ESB	O
)	O
.	O
</s>
<s>
Database	B-General_Concept
access	O
services	O
are	O
often	O
characterised	O
as	O
middleware	B-General_Concept
.	O
</s>
<s>
Examples	O
of	O
database-oriented	O
middleware	B-General_Concept
include	O
ODBC	B-Application
,	O
JDBC	B-Language
and	O
transaction	B-General_Concept
processing	I-General_Concept
monitors	I-General_Concept
.	O
</s>
<s>
Distributed	B-Architecture
computing	I-Architecture
system	O
middleware	B-General_Concept
can	O
loosely	O
be	O
divided	O
into	O
two	O
categories	O
—	O
those	O
that	O
provide	O
human-time	O
services	O
(	O
such	O
as	O
web	O
request	O
servicing	O
)	O
and	O
those	O
that	O
perform	O
in	O
machine-time	O
.	O
</s>
<s>
This	O
latter	O
middleware	B-General_Concept
is	O
somewhat	O
standardized	O
through	O
the	O
Service	O
Availability	O
Forum	O
and	O
is	O
commonly	O
used	O
in	O
complex	O
,	O
embedded	B-Architecture
systems	I-Architecture
within	O
telecom	O
,	O
defence	O
and	O
aerospace	O
industries	O
.	O
</s>
<s>
Many	O
definitions	O
exist	O
regarding	O
the	O
categorization	O
of	O
middleware	B-General_Concept
specifying	O
either	O
on	O
the	O
field	O
that	O
it	O
is	O
used	O
or	O
the	O
application	O
module	O
it	O
serves	O
.	O
</s>
<s>
In	O
recent	O
bibliography	O
,	O
the	O
main	O
categories	O
of	O
middleware	B-General_Concept
are	O
the	O
following	O
:	O
</s>
<s>
Transactional	O
:	O
Processing	O
of	O
multiple	O
synchronous/	O
asynchronous	O
transactions	O
,	O
serving	O
as	O
a	O
cluster	O
of	O
associated	O
requests	O
from	O
distributed	B-Architecture
systems	I-Architecture
such	O
as	O
bank	O
transactions	O
or	O
credit	O
card	O
payments	O
.	O
</s>
<s>
Object-oriented	O
:	O
Similar	O
to	O
procedural	O
middleware	B-General_Concept
,	O
however	O
,	O
this	O
type	O
of	O
middleware	B-General_Concept
incorporates	O
object-oriented	O
programming	O
design	O
principles	O
.	O
</s>
<s>
The	O
term	O
middleware	B-General_Concept
is	O
used	O
in	O
other	O
contexts	O
as	O
well	O
.	O
</s>
<s>
Middleware	B-General_Concept
is	O
sometimes	O
used	O
in	O
a	O
similar	O
sense	O
to	O
a	O
software	B-Application
driver	I-Application
,	O
an	O
abstraction	O
layer	O
that	O
hides	O
detail	O
about	O
hardware	O
devices	O
or	O
other	O
software	O
from	O
an	O
application	O
.	O
</s>
<s>
The	O
Android	B-Application
operating	I-Application
system	I-Application
uses	O
the	O
Linux	B-Application
kernel	O
at	O
its	O
core	O
,	O
and	O
also	O
provides	O
an	O
application	B-Application
framework	I-Application
that	O
developers	B-Application
incorporate	O
into	O
their	O
applications	O
.	O
</s>
<s>
In	O
addition	O
,	O
Android	B-Application
provides	O
a	O
middleware	B-General_Concept
layer	O
including	O
libraries	B-Library
that	O
provide	O
services	O
such	O
as	O
data	O
storage	O
,	O
screen	O
display	O
,	O
multimedia	O
,	O
and	O
web	O
browsing	O
.	O
</s>
<s>
Because	O
the	O
middleware	B-General_Concept
libraries	B-Library
are	O
compiled	B-Language
to	O
machine	B-Language
language	I-Language
,	O
services	O
execute	O
quickly	O
.	O
</s>
<s>
Middleware	B-General_Concept
libraries	B-Library
also	O
implement	O
device-specific	O
functions	O
,	O
so	O
applications	O
and	O
the	O
application	B-Application
framework	I-Application
need	O
not	O
concern	O
themselves	O
with	O
variations	O
between	O
various	O
Android	B-Application
devices	O
.	O
</s>
<s>
Android	B-Application
's	O
middleware	B-General_Concept
layer	O
also	O
contains	O
the	O
ART	B-Application
virtual	B-Architecture
machine	I-Architecture
and	O
its	O
core	O
Java	B-Language
application	O
libraries	B-Library
.	O
</s>
<s>
Middleware	B-General_Concept
also	O
refers	O
to	O
the	O
software	O
that	O
separates	O
two	O
or	O
more	O
APIs	B-Application
and	O
provides	O
services	O
such	O
as	O
rate-limiting	O
,	O
authentication	O
,	O
and	O
logging	O
.	O
</s>
<s>
Game	O
engine	O
software	O
such	O
as	O
Gamebryo	O
and	O
RenderWare	O
are	O
sometimes	O
described	O
as	O
middleware	B-General_Concept
,	O
because	O
they	O
provide	O
many	O
services	O
to	O
simplify	O
game	O
development	O
.	O
</s>
<s>
In	O
simulation	O
technology	O
,	O
middleware	B-General_Concept
is	O
generally	O
used	O
in	O
the	O
context	O
of	O
the	O
high	B-Operating_System
level	I-Operating_System
architecture	I-Operating_System
(	O
HLA	O
)	O
that	O
applies	O
to	O
many	O
distributed	O
simulations	O
.	O
</s>
<s>
It	O
is	O
a	O
layer	O
of	O
software	O
that	O
lies	O
between	O
the	O
application	O
code	O
and	O
the	O
run-time	B-Application
infrastructure	I-Application
.	O
</s>
<s>
Middleware	B-General_Concept
generally	O
consists	O
of	O
a	O
library	O
of	O
functions	O
,	O
and	O
enables	O
a	O
number	O
of	O
applications	O
—	O
simulations	O
or	O
federates	O
in	O
HLA	O
terminology	O
—	O
to	O
page	B-Architecture
these	O
functions	O
from	O
the	O
common	O
library	O
rather	O
than	O
re-create	O
them	O
for	O
each	O
application	O
.	O
</s>
<s>
Wireless	O
networking	O
developers	B-Application
can	O
use	O
middleware	B-General_Concept
to	O
meet	O
the	O
challenges	O
associated	O
with	O
a	O
wireless	B-Architecture
sensor	I-Architecture
network	I-Architecture
(	O
WSN	B-Architecture
)	O
.	O
</s>
<s>
Implementing	O
a	O
middleware	B-General_Concept
application	O
allows	O
WSN	B-Architecture
developers	B-Application
to	O
integrate	O
operating	B-General_Concept
systems	I-General_Concept
and	O
hardware	O
with	O
the	O
wide	O
variety	O
of	O
various	O
applications	O
that	O
are	O
currently	O
available	O
.	O
</s>
<s>
The	O
QNX	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
offers	O
middleware	B-General_Concept
for	O
providing	O
multimedia	O
services	O
for	O
use	O
in	O
automobiles	O
,	O
aircraft	O
and	O
other	O
environments	O
.	O
</s>
<s>
Radio-frequency	B-Application
identification	I-Application
(	O
RFID	B-Application
)	O
software	O
toolkits	O
provide	O
middleware	B-General_Concept
to	O
filter	O
noisy	O
and	O
redundant	O
raw	O
data	O
.	O
</s>
