<s>
Enterprise	B-Architecture
application	I-Architecture
integration	I-Architecture
(	O
EAI	O
)	O
is	O
the	O
use	O
of	O
software	O
and	O
computer	O
systems	O
 '	O
architectural	O
principles	O
to	O
integrate	O
a	O
set	O
of	O
enterprise	B-Application
computer	I-Application
applications	I-Application
.	O
</s>
<s>
Enterprise	B-Architecture
application	I-Architecture
integration	I-Architecture
is	O
an	O
integration	O
framework	O
composed	O
of	O
a	O
collection	O
of	O
technologies	O
and	O
services	O
which	O
form	O
a	O
middleware	B-General_Concept
or	O
"	O
middleware	B-General_Concept
framework	O
"	O
to	O
enable	O
integration	O
of	O
systems	O
and	O
applications	O
across	O
an	O
enterprise	O
.	O
</s>
<s>
Many	O
types	O
of	O
business	O
software	O
such	O
as	O
supply	O
chain	O
management	O
applications	O
,	O
ERP	O
systems	O
,	O
CRM	O
applications	O
for	O
managing	O
customers	O
,	O
business	B-General_Concept
intelligence	I-General_Concept
applications	O
,	O
payroll	O
,	O
and	O
human	O
resources	O
systems	O
typically	O
cannot	O
communicate	O
with	O
one	O
another	O
in	O
order	O
to	O
share	O
data	O
or	O
business	O
rules	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
such	O
applications	O
are	O
sometimes	O
referred	O
to	O
as	O
islands	O
of	O
automation	O
or	O
information	B-Application
silos	I-Application
.	O
</s>
<s>
Enterprise	B-Architecture
application	I-Architecture
integration	I-Architecture
is	O
the	O
process	O
of	O
linking	O
such	O
applications	O
within	O
a	O
single	O
organization	O
together	O
in	O
order	O
to	O
simplify	O
and	O
automate	O
business	O
processes	O
to	O
the	O
greatest	O
extent	O
possible	O
,	O
while	O
at	O
the	O
same	O
time	O
avoiding	O
having	O
to	O
make	O
sweeping	O
changes	O
to	O
the	O
existing	O
applications	O
or	O
data	O
structures	O
.	O
</s>
<s>
Applications	O
can	O
be	O
linked	O
either	O
at	O
the	O
back-end	O
via	O
APIs	B-General_Concept
or	O
(	O
seldom	O
)	O
the	O
front-end	O
(	O
GUI	B-Application
)	O
.	O
</s>
<s>
The	O
various	O
systems	O
that	O
need	O
to	O
be	O
linked	O
together	O
may	O
reside	O
on	O
different	O
operating	B-General_Concept
systems	I-General_Concept
,	O
use	O
different	O
database	O
solutions	O
or	O
computer	B-Language
languages	I-Language
,	O
or	O
different	O
date	O
and	O
time	O
formats	O
,	O
or	O
could	O
be	O
legacy	B-Device
systems	I-Device
that	O
are	O
no	O
longer	O
supported	O
by	O
the	O
vendor	O
who	O
originally	O
created	O
them	O
.	O
</s>
<s>
If	O
integration	O
is	O
applied	O
without	O
following	O
a	O
structured	O
EAI	O
approach	O
,	O
point-to-point	B-Architecture
connections	O
grow	O
across	O
an	O
organization	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
number	O
of	O
connections	O
needed	O
to	O
have	O
fully	O
meshed	O
point-to-point	B-Architecture
connections	O
,	O
with	O
points	O
,	O
is	O
given	O
by	O
(	O
see	O
binomial	O
coefficient	O
)	O
.	O
</s>
<s>
Thus	O
,	O
for	O
ten	O
applications	O
to	O
be	O
fully	O
integrated	O
point-to-point	B-Architecture
,	O
point-to-point	B-Architecture
connections	O
are	O
needed	O
,	O
following	O
a	O
quadratic	O
growth	O
pattern	O
.	O
</s>
<s>
A	O
middleware	B-General_Concept
analyst	O
attending	O
to	O
EAI	O
will	O
often	O
look	O
at	O
the	O
system	O
of	O
systems	O
.	O
</s>
<s>
Data	B-General_Concept
integration	I-General_Concept
:	O
Ensures	O
that	O
information	O
in	O
multiple	O
systems	O
is	O
kept	O
consistent	O
.	O
</s>
<s>
This	O
is	O
also	O
known	O
as	O
enterprise	B-General_Concept
information	I-General_Concept
integration	I-General_Concept
(	O
EII	O
)	O
.	O
</s>
<s>
Whenever	O
an	O
interesting	O
event	O
occurs	O
in	O
an	O
application	O
(	O
for	O
instance	O
,	O
new	O
information	O
is	O
created	O
or	O
a	O
new	O
transaction	B-General_Concept
completed	O
)	O
an	O
integration	O
module	O
in	O
the	O
EAI	O
system	O
is	O
notified	O
.	O
</s>
<s>
An	O
integration	O
operation	O
could	O
be	O
short-lived	O
(	O
e.g.	O
,	O
keeping	O
data	O
in	O
sync	O
across	O
two	O
applications	O
could	O
be	O
completed	O
within	O
a	O
second	O
)	O
or	O
long-lived	O
(	O
e.g.	O
,	O
one	O
of	O
the	O
steps	O
could	O
involve	O
the	O
EAI	O
system	O
interacting	O
with	O
a	O
human	O
work	B-Protocol
flow	I-Protocol
application	O
for	O
approval	O
of	O
a	O
loan	O
that	O
takes	O
hours	O
or	O
days	O
to	O
complete	O
)	O
.	O
</s>
<s>
There	O
are	O
two	O
major	O
topologies	O
:	O
hub-and-spoke	O
,	O
and	O
bus	B-Application
.	O
</s>
<s>
In	O
the	O
bus	B-Application
model	O
,	O
the	O
EAI	O
system	O
is	O
the	O
bus	B-Application
(	O
or	O
is	O
implemented	O
as	O
a	O
resident	O
module	O
in	O
an	O
already	O
existing	O
message	B-Application
bus	I-Application
or	O
message-oriented	B-Application
middleware	I-Application
)	O
.	O
</s>
<s>
Bus/hub	O
This	O
is	O
usually	O
implemented	O
by	O
enhancing	O
standard	O
middleware	B-General_Concept
products	O
(	O
application	B-Application
server	I-Application
,	O
message	B-Application
bus	I-Application
)	O
or	O
implemented	O
as	O
a	O
stand-alone	O
program	O
(	O
i.e.	O
,	O
does	O
not	O
use	O
any	O
middleware	B-General_Concept
)	O
,	O
acting	O
as	O
its	O
own	O
middleware	B-General_Concept
.	O
</s>
<s>
Application	O
connectivity	O
The	O
bus/hub	O
connects	O
to	O
applications	O
through	O
a	O
set	O
of	O
adapters	O
(	O
also	O
referred	O
to	O
as	O
connectors	O
)	O
.	O
</s>
<s>
The	O
adapter	O
performs	O
one-way	O
communication(unidirectional )	O
,	O
performing	O
requests	O
from	O
the	O
hub	O
against	O
the	O
application	O
,	O
and	O
notifying	O
the	O
hub	O
when	O
an	O
event	O
of	O
interest	O
occurs	O
in	O
the	O
application	O
(	O
a	O
new	O
record	O
inserted	O
,	O
a	O
transaction	B-General_Concept
completed	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
Adapters	O
can	O
be	O
specific	O
to	O
an	O
application	O
(	O
e.g.	O
,	O
built	O
against	O
the	O
application	O
vendor	O
's	O
client	O
libraries	O
)	O
or	O
specific	O
to	O
a	O
class	O
of	O
applications	O
(	O
e.g.	O
,	O
can	O
interact	O
with	O
any	O
application	O
through	O
a	O
standard	O
communication	O
protocol	O
,	O
such	O
as	O
SOAP	B-Application
,	O
SMTP	B-Protocol
or	O
Action	B-Protocol
Message	I-Protocol
Format	I-Protocol
(	O
AMF	O
)	O
)	O
.	O
</s>
<s>
The	O
adapter	O
could	O
reside	O
in	O
the	O
same	O
process	O
space	O
as	O
the	O
bus/hub	O
or	O
execute	O
in	O
a	O
remote	O
location	O
and	O
interact	O
with	O
the	O
hub/bus	O
through	O
industry-standard	O
protocols	O
such	O
as	O
message	O
queues	O
,	O
web	O
services	O
,	O
or	O
even	O
use	O
a	O
proprietary	O
protocol	O
.	O
</s>
<s>
In	O
the	O
Java	B-Language
world	O
,	O
standards	O
such	O
as	O
JCA	B-Language
allow	O
adapters	O
to	O
be	O
created	O
in	O
a	O
vendor-neutral	O
manner	O
.	O
</s>
<s>
Data	O
format	O
and	O
transformation	B-General_Concept
To	O
avoid	O
every	O
adapter	O
having	O
to	O
convert	O
data	O
to/from	O
every	O
other	O
application	O
's	O
formats	O
,	O
EAI	O
systems	O
usually	O
stipulate	O
an	O
application-independent	O
(	O
or	O
common	O
)	O
data	O
format	O
.	O
</s>
<s>
The	O
EAI	O
system	O
usually	O
provides	O
a	O
data	B-General_Concept
transformation	I-General_Concept
service	O
as	O
well	O
to	O
help	O
convert	O
between	O
application-specific	O
and	O
common	O
formats	O
.	O
</s>
<s>
This	O
is	O
done	O
in	O
two	O
steps	O
:	O
the	O
adapter	O
converts	O
information	O
from	O
the	O
application	O
's	O
format	O
to	O
the	O
bus	B-Application
's	O
common	O
format	O
.	O
</s>
<s>
These	O
modules	O
could	O
be	O
implemented	O
in	O
different	O
ways	O
:	O
on	O
Java-based	O
EAI	O
systems	O
,	O
these	O
could	O
be	O
web	B-Application
applications	I-Application
or	O
EJBs	B-Language
or	O
even	O
POJOs	O
that	O
conform	O
to	O
the	O
EAI	O
system	O
's	O
specifications	O
.	O
</s>
<s>
Support	O
for	O
transactions	O
When	O
used	O
for	O
process	O
integration	O
,	O
the	O
EAI	O
system	O
also	O
provides	O
transactional	O
consistency	O
across	O
applications	O
by	O
executing	O
all	O
integration	O
operations	O
across	O
all	O
applications	O
in	O
a	O
single	O
overarching	O
distributed	O
transaction	B-General_Concept
(	O
using	O
two-phase	B-General_Concept
commit	I-General_Concept
protocols	I-General_Concept
or	O
compensating	B-General_Concept
transactions	I-General_Concept
)	O
.	O
</s>
<s>
Currently	O
,	O
there	O
are	O
many	O
variations	O
of	O
thought	O
on	O
what	O
constitutes	O
the	O
best	O
infrastructure	O
,	O
component	O
model	O
,	O
and	O
standards	O
structure	O
for	O
Enterprise	B-Architecture
Application	I-Architecture
Integration	I-Architecture
.	O
</s>
<s>
There	O
seems	O
to	O
be	O
a	O
consensus	O
that	O
four	O
components	O
are	O
essential	O
for	O
a	O
modern	O
enterprise	B-Architecture
application	I-Architecture
integration	I-Architecture
architecture	O
:	O
</s>
<s>
This	O
can	O
be	O
accomplished	O
through	O
integration	O
servers	O
(	O
like	O
the	O
School	O
Interoperability	O
Framework	O
(	O
SIF	O
)	O
Zone	O
Integration	O
Servers	O
)	O
or	O
through	O
similar	O
software	O
like	O
the	O
enterprise	B-Application
service	I-Application
bus	I-Application
(	O
ESB	O
)	O
model	O
that	O
acts	O
as	O
a	O
services	O
manager	O
.	O
</s>
<s>
An	O
independent	O
data	O
model	O
based	O
on	O
a	O
standard	O
data	O
structure	O
,	O
also	O
known	O
as	O
a	O
canonical	B-Application
data	I-Application
model	I-Application
.	O
</s>
<s>
It	O
appears	O
that	O
XML	B-Protocol
and	O
the	O
use	O
of	O
XML	B-Protocol
style	O
sheets	O
have	O
become	O
the	O
de	O
facto	O
and	O
in	O
some	O
cases	O
de	O
jure	O
standard	O
for	O
this	O
uniform	O
business	O
language	O
.	O
</s>
<s>
A	O
system	O
model	O
that	O
defines	O
the	O
APIs	B-General_Concept
,	O
data	O
flow	O
and	O
rules	O
of	O
engagement	O
to	O
the	O
system	O
such	O
that	O
components	O
can	O
be	O
built	O
to	O
interface	O
with	O
it	O
in	O
a	O
standardized	O
way	O
.	O
</s>
<s>
This	O
central	O
control	O
approach	O
can	O
be	O
extremely	O
scalable	B-Architecture
and	O
highly	O
evolvable	O
.	O
</s>
<s>
Enterprise	B-Architecture
Application	I-Architecture
Integration	I-Architecture
is	O
related	O
to	O
middleware	B-General_Concept
technologies	O
such	O
as	O
message-oriented	B-Application
middleware	I-Application
(	O
MOM	B-Application
)	O
,	O
and	O
data	O
representation	O
technologies	O
such	O
as	O
XML	B-Protocol
or	O
JSON	B-General_Concept
.	O
</s>
<s>
Enterprise	B-Architecture
Application	I-Architecture
Integration	I-Architecture
tends	O
to	O
be	O
data	O
centric	O
.	O
</s>
<s>
In	O
the	O
near	O
future	O
,	O
it	O
will	O
come	O
to	O
include	O
content	B-Protocol
integration	I-Protocol
and	O
business	O
processes	O
.	O
</s>
