<s>
SOAP	B-Protocol
(	O
formerly	O
a	O
backronym	O
for	O
Simple	B-Protocol
Object	I-Protocol
Access	I-Protocol
Protocol	I-Protocol
)	O
is	O
a	O
messaging	O
protocol	O
specification	O
for	O
exchanging	O
structured	O
information	O
in	O
the	O
implementation	O
of	O
web	O
services	O
in	O
computer	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
It	O
uses	O
XML	B-Protocol
Information	O
Set	O
for	O
its	O
message	O
format	O
,	O
and	O
relies	O
on	O
application	B-Application
layer	I-Application
protocols	O
,	O
most	O
often	O
Hypertext	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
HTTP	B-Protocol
)	O
,	O
although	O
some	O
legacy	O
systems	O
communicate	O
over	O
Simple	B-Protocol
Mail	I-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
SMTP	B-Protocol
)	O
,	O
for	O
message	O
negotiation	O
and	O
transmission	O
.	O
</s>
<s>
SOAP	B-Protocol
allows	O
developers	O
to	O
invoke	O
processes	O
running	O
on	O
different	O
operating	O
systems	O
(	O
such	O
as	O
Windows	B-Application
,	O
macOS	B-Application
,	O
and	O
Linux	B-Application
)	O
to	O
authenticate	O
,	O
authorize	O
,	O
and	O
communicate	O
using	O
Extensible	B-Protocol
Markup	I-Protocol
Language	I-Protocol
(	O
XML	B-Protocol
)	O
.	O
</s>
<s>
Since	O
Web	O
protocols	O
like	O
HTTP	B-Protocol
are	O
installed	O
and	O
running	O
on	O
practically	O
all	O
operating	O
systems	O
,	O
SOAP	B-Protocol
allows	O
clients	O
to	O
invoke	O
web	O
services	O
and	O
receive	O
responses	O
independent	O
of	O
language	O
and	O
platforms	O
.	O
</s>
<s>
SOAP	B-Protocol
provides	O
the	O
Messaging	O
Protocol	O
layer	O
of	O
a	O
web	O
services	O
protocol	O
stack	O
for	O
web	O
services	O
.	O
</s>
<s>
It	O
is	O
an	O
XML-based	O
protocol	O
consisting	O
of	O
three	O
parts	O
:	O
</s>
<s>
SOAP	B-Protocol
has	O
three	O
major	O
characteristics	O
:	O
</s>
<s>
As	O
an	O
example	O
of	O
what	O
SOAP	B-Protocol
procedures	O
can	O
do	O
,	O
an	O
application	O
can	O
send	O
a	O
SOAP	B-Protocol
request	I-Protocol
to	O
a	O
server	O
that	O
has	O
web	O
services	O
enabled	O
—	O
such	O
as	O
a	O
real-estate	O
price	O
database	O
—	O
with	O
the	O
parameters	O
for	O
a	O
search	O
.	O
</s>
<s>
The	O
server	O
then	O
returns	O
a	O
SOAP	B-Protocol
response	O
(	O
an	O
XML-formatted	O
document	O
)	O
with	O
the	O
resulting	O
data	O
,	O
e.g.	O
,	O
prices	O
,	O
location	O
,	O
features	O
.	O
</s>
<s>
The	O
SOAP	B-Protocol
architecture	O
consists	O
of	O
several	O
layers	O
of	O
specifications	O
for	O
:	O
</s>
<s>
SOAP	B-Protocol
evolved	O
as	O
a	O
successor	O
of	O
XML-RPC	B-Protocol
,	O
though	O
it	O
borrows	O
its	O
transport	O
and	O
interaction	O
neutrality	O
from	O
Web	O
Service	O
Addressing	O
and	O
the	O
envelope/header/body	O
from	O
elsewhere	O
(	O
probably	O
from	O
WDDX	B-Protocol
)	O
.	O
</s>
<s>
SOAP	B-Protocol
was	O
designed	O
as	O
an	O
object-access	O
protocol	O
and	O
released	O
as	O
XML-RPC	B-Protocol
in	O
June	O
1998	O
as	O
part	O
of	O
Frontier	O
5.1	O
by	O
Dave	O
Winer	O
,	O
Don	O
Box	O
,	O
Bob	O
Atkinson	O
,	O
and	O
Mohsen	O
Al-Ghosein	O
for	O
Microsoft	O
,	O
where	O
Atkinson	O
and	O
Al-Ghosein	O
were	O
working	O
.	O
</s>
<s>
Because	O
of	O
Microsoft	O
's	O
hesitation	O
,	O
Dave	O
Winer	O
shipped	O
XML-RPC	B-Protocol
in	O
1998	O
.	O
</s>
<s>
The	O
SOAP	B-Protocol
specification	O
was	O
maintained	O
by	O
the	O
XML	B-Protocol
Protocol	O
Working	O
Group	O
of	O
the	O
World	O
Wide	O
Web	O
Consortium	O
until	O
the	O
group	O
was	O
closed	O
10	O
July	O
2009	O
.	O
</s>
<s>
SOAP	B-Protocol
originally	O
stood	O
for	O
"	O
Simple	B-Protocol
Object	I-Protocol
Access	I-Protocol
Protocol	I-Protocol
"	O
but	O
version	O
1.2	O
of	O
the	O
standard	O
dropped	O
this	O
acronym	O
.	O
</s>
<s>
After	O
SOAP	B-Protocol
was	O
first	O
introduced	O
,	O
it	O
became	O
the	O
underlying	O
layer	O
of	O
a	O
more	O
complex	O
set	O
of	O
web	O
services	O
,	O
based	O
on	O
WSDL	O
,	O
XSD	O
and	O
UDDI	O
.	O
</s>
<s>
These	O
different	O
services	O
,	O
especially	O
UDDI	O
,	O
have	O
proved	O
to	O
be	O
of	O
far	O
less	O
interest	O
,	O
but	O
an	O
appreciation	O
of	O
them	O
gives	O
a	O
complete	O
understanding	O
of	O
the	O
expected	O
role	O
of	O
SOAP	B-Protocol
compared	O
to	O
how	O
web	O
services	O
have	O
actually	O
evolved	O
.	O
</s>
<s>
SOAP	B-Protocol
specification	O
can	O
be	O
broadly	O
defined	O
to	O
be	O
consisting	O
of	O
the	O
following	O
three	O
conceptual	O
components	O
:	O
protocol	O
concepts	O
,	O
encapsulation	O
concepts	O
and	O
network	O
concepts	O
.	O
</s>
<s>
SOAP	B-Protocol
This	O
is	O
a	O
set	O
of	O
rules	O
formalizing	O
and	O
governing	O
the	O
format	O
and	O
processing	O
rules	O
for	O
information	O
exchanged	O
between	O
a	O
SOAP	B-Protocol
sender	O
and	O
a	O
SOAP	B-Protocol
receiver	O
.	O
</s>
<s>
SOAP	B-Protocol
nodes	B-Protocol
These	O
are	O
physical/logical	O
machines	O
with	O
processing	O
units	O
which	O
are	O
used	O
to	O
transmit/forward	O
,	O
receive	O
and	O
process	O
SOAP	B-Protocol
messages	O
.	O
</s>
<s>
These	O
are	O
analogous	O
to	O
nodes	B-Protocol
in	O
a	O
network	O
.	O
</s>
<s>
SOAP	B-Protocol
roles	O
Over	O
the	O
path	O
of	O
a	O
SOAP	B-Protocol
message	O
,	O
all	O
nodes	B-Protocol
assume	O
a	O
specific	O
role	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
role	O
"	O
none	O
"	O
means	O
that	O
no	O
node	O
will	O
process	O
the	O
SOAP	B-Protocol
header	O
in	O
any	O
way	O
and	O
simply	O
transmit	O
the	O
message	O
along	O
its	O
path	O
.	O
</s>
<s>
SOAP	B-Protocol
protocol	O
binding	O
A	O
SOAP	B-Protocol
message	O
needs	O
to	O
work	O
in	O
conjunction	O
with	O
other	O
protocols	O
to	O
be	O
transferred	O
over	O
a	O
network	O
.	O
</s>
<s>
For	O
example	O
,	O
a	O
SOAP	B-Protocol
message	O
could	O
use	O
TCP	B-Protocol
as	O
a	O
lower	O
layer	O
protocol	O
to	O
transfer	O
messages	O
.	O
</s>
<s>
These	O
bindings	O
are	O
defined	O
in	O
the	O
SOAP	B-Protocol
protocol	O
binding	O
framework	O
.	O
</s>
<s>
SOAP	B-Protocol
features	O
SOAP	B-Protocol
provides	O
a	O
messaging	O
framework	O
only	O
.	O
</s>
<s>
There	O
are	O
rules	O
to	O
be	O
followed	O
when	O
adding	O
features	O
to	O
the	O
SOAP	B-Protocol
framework	O
.	O
</s>
<s>
SOAP	B-Protocol
module	O
A	O
collection	O
of	O
specifications	O
regarding	O
the	O
semantics	O
of	O
SOAP	B-Protocol
header	O
to	O
describe	O
any	O
new	O
features	O
being	O
extended	O
upon	O
SOAP	B-Protocol
.	O
</s>
<s>
SOAP	B-Protocol
requires	O
modules	O
to	O
adhere	O
to	O
prescribed	O
rules	O
.	O
</s>
<s>
SOAP	B-Protocol
message	O
Represents	O
the	O
information	O
being	O
exchanged	O
between	O
2	O
SOAP	B-Protocol
nodes	B-Protocol
.	O
</s>
<s>
SOAP	B-Protocol
envelope	O
It	O
is	O
the	O
enclosing	O
element	O
of	O
an	O
XML	B-Protocol
message	O
identifying	O
it	O
as	O
a	O
SOAP	B-Protocol
message	O
.	O
</s>
<s>
SOAP	B-Protocol
header	O
block	O
A	O
SOAP	B-Protocol
header	O
can	O
contain	O
more	O
than	O
one	O
of	O
these	O
blocks	O
,	O
each	O
being	O
a	O
discrete	O
computational	O
block	O
within	O
the	O
header	O
.	O
</s>
<s>
In	O
general	O
,	O
the	O
SOAP	B-Protocol
role	O
information	O
is	O
used	O
to	O
target	O
nodes	B-Protocol
on	O
the	O
path	O
.	O
</s>
<s>
A	O
header	O
block	O
is	O
said	O
to	O
be	O
targeted	O
at	O
a	O
SOAP	B-Protocol
node	O
if	O
the	O
SOAP	B-Protocol
role	O
for	O
the	O
header	O
block	O
is	O
the	O
name	O
of	O
a	O
role	O
in	O
which	O
the	O
SOAP	B-Protocol
node	O
operates	O
.	O
</s>
<s>
(	O
ex	O
:	O
A	O
SOAP	B-Protocol
header	O
block	O
with	O
role	O
attribute	O
as	O
ultimateReceiver	O
is	O
targeted	O
only	O
at	O
the	O
destination	O
node	O
which	O
has	O
this	O
role	O
.	O
</s>
<s>
SOAP	B-Protocol
header	O
A	O
collection	O
of	O
one	O
or	O
more	O
header	O
blocks	O
targeted	O
at	O
each	O
SOAP	B-Protocol
receiver	O
.	O
</s>
<s>
SOAP	B-Protocol
body	O
Contains	O
the	O
body	O
of	O
the	O
message	O
intended	O
for	O
the	O
SOAP	B-Protocol
receiver	O
.	O
</s>
<s>
The	O
interpretation	O
and	O
processing	O
of	O
SOAP	B-Protocol
body	O
is	O
defined	O
by	O
header	O
blocks	O
.	O
</s>
<s>
SOAP	B-Protocol
fault	O
In	O
case	O
a	O
SOAP	B-Protocol
node	O
fails	O
to	O
process	O
a	O
SOAP	B-Protocol
message	O
,	O
it	O
adds	O
the	O
fault	O
information	O
to	O
the	O
SOAP	B-Protocol
fault	O
element	O
.	O
</s>
<s>
This	O
element	O
is	O
contained	O
within	O
the	O
SOAP	B-Protocol
body	O
as	O
a	O
child	O
element	O
.	O
</s>
<s>
SOAP	B-Protocol
sender	O
The	O
node	O
that	O
transmits	O
a	O
SOAP	B-Protocol
message	O
.	O
</s>
<s>
SOAP	B-Protocol
receiver	O
The	O
node	O
receiving	O
a	O
SOAP	B-Protocol
message	O
.	O
</s>
<s>
SOAP	B-Protocol
message	O
path	O
The	O
path	O
consisting	O
of	O
all	O
the	O
nodes	B-Protocol
that	O
the	O
SOAP	B-Protocol
message	O
traversed	O
to	O
reach	O
the	O
destination	O
node	O
.	O
</s>
<s>
Initial	O
SOAP	B-Protocol
sender	O
This	O
is	O
the	O
node	O
which	O
originated	O
the	O
SOAP	B-Protocol
message	O
to	O
be	O
transmitted	O
.	O
</s>
<s>
This	O
is	O
the	O
root	O
of	O
the	O
SOAP	B-Protocol
message	O
path	O
.	O
</s>
<s>
SOAP	B-Protocol
intermediary	O
All	O
the	O
nodes	B-Protocol
in	O
between	O
the	O
SOAP	B-Protocol
originator	O
and	O
the	O
intended	O
SOAP	B-Protocol
destination	O
.	O
</s>
<s>
It	O
processes	O
the	O
SOAP	B-Protocol
header	O
blocks	O
targeted	O
at	O
it	O
and	O
acts	O
to	O
forward	O
a	O
SOAP	B-Protocol
message	O
towards	O
an	O
ultimate	O
SOAP	B-Protocol
receiver	O
.	O
</s>
<s>
Ultimate	O
SOAP	B-Protocol
receiver	O
The	O
destination	O
receiver	O
of	O
the	O
SOAP	B-Protocol
message	O
.	O
</s>
<s>
The	O
SOAP	B-Protocol
specification	O
defines	O
the	O
messaging	O
framework	O
,	O
which	O
consists	O
of	O
:	O
</s>
<s>
A	O
SOAP	B-Protocol
message	O
is	O
an	O
ordinary	O
XML	B-Protocol
document	I-Protocol
containing	O
the	O
following	O
elements	O
:	O
</s>
<s>
Both	O
SMTP	B-Protocol
and	O
HTTP	B-Protocol
are	O
valid	O
application	B-Application
layer	I-Application
protocols	O
used	O
as	O
transport	O
for	O
SOAP	B-Protocol
,	O
but	O
HTTP	B-Protocol
has	O
gained	O
wider	O
acceptance	O
as	O
it	O
works	O
well	O
with	O
today	O
's	O
internet	O
infrastructure	O
;	O
specifically	O
,	O
HTTP	B-Protocol
works	O
well	O
with	O
network	B-Application
firewalls	I-Application
.	O
</s>
<s>
SOAP	B-Protocol
may	O
also	O
be	O
used	O
over	O
HTTPS	B-Protocol
(	O
which	O
is	O
the	O
same	O
protocol	O
as	O
HTTP	B-Protocol
at	O
the	O
application	O
level	O
,	O
but	O
uses	O
an	O
encrypted	B-Protocol
transport	I-Protocol
protocol	I-Protocol
underneath	O
)	O
with	O
either	O
simple	O
or	O
mutual	O
authentication	O
;	O
this	O
is	O
the	O
advocated	O
WS-I	O
method	O
to	O
provide	O
web	O
service	O
security	O
as	O
stated	O
in	O
the	O
WS-I	O
Basic	O
Profile	O
1.1	O
.	O
</s>
<s>
This	O
is	O
a	O
major	O
advantage	O
over	O
other	O
distributed	O
protocols	O
like	O
GIOP/IIOP	B-Operating_System
or	O
DCOM	B-Operating_System
,	O
which	O
are	O
normally	O
filtered	O
by	O
firewalls	B-Application
.	O
</s>
<s>
SOAP	B-Protocol
over	O
AMQP	B-Operating_System
is	O
yet	O
another	O
possibility	O
that	O
some	O
implementations	O
support	O
.	O
</s>
<s>
SOAP	B-Protocol
also	O
has	O
an	O
advantage	O
over	O
DCOM	B-Operating_System
that	O
it	O
is	O
unaffected	O
by	O
security	O
rights	O
configured	O
on	O
the	O
machines	O
that	O
require	O
knowledge	O
of	O
both	O
transmitting	O
and	O
receiving	O
nodes	B-Protocol
.	O
</s>
<s>
This	O
lets	O
SOAP	B-Protocol
be	O
loosely	O
coupled	O
in	O
a	O
way	O
that	O
is	O
not	O
possible	O
with	O
DCOM	B-Operating_System
.	O
</s>
<s>
There	O
is	O
also	O
the	O
SOAP-over-UDP	O
OASIS	O
standard	O
.	O
</s>
<s>
XML	B-Protocol
Information	O
Set	O
was	O
chosen	O
as	O
the	O
standard	O
message	O
format	O
because	O
of	O
its	O
widespread	O
use	O
by	O
major	O
corporations	O
and	O
open	B-License
source	I-License
development	O
efforts	O
.	O
</s>
<s>
Typically	O
,	O
XML	B-Protocol
Information	O
Set	O
is	O
serialized	B-Application
as	O
XML	B-Protocol
.	O
</s>
<s>
A	O
wide	O
variety	O
of	O
freely	O
available	O
tools	B-Application
significantly	O
eases	O
the	O
transition	O
to	O
a	O
SOAP-based	O
implementation	O
.	O
</s>
<s>
The	O
somewhat	O
lengthy	O
syntax	B-Application
of	O
XML	B-Protocol
can	O
be	O
both	O
a	O
benefit	O
and	O
a	O
drawback	O
.	O
</s>
<s>
For	O
example	O
,	O
CORBA	B-Architecture
,	O
GIOP	B-Operating_System
,	O
ICE	B-Operating_System
,	O
and	O
DCOM	B-Operating_System
use	O
much	O
shorter	O
,	O
binary	O
message	O
formats	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
hardware	O
appliances	O
are	O
available	O
to	O
accelerate	O
processing	O
of	O
XML	B-Protocol
messages	O
.	O
</s>
<s>
Binary	B-Protocol
XML	I-Protocol
is	O
also	O
being	O
explored	O
as	O
a	O
means	O
for	O
streamlining	O
the	O
throughput	O
requirements	O
of	O
XML	B-Protocol
.	O
</s>
<s>
XML	B-Protocol
messages	O
by	O
their	O
self-documenting	O
nature	O
usually	O
have	O
more	O
'	O
overhead	O
 '	O
(	O
e.g.	O
,	O
headers	O
,	O
nested	O
tags	O
,	O
delimiters	O
)	O
than	O
actual	O
data	O
in	O
contrast	O
to	O
earlier	O
protocols	O
where	O
the	O
overhead	O
was	O
usually	O
a	O
relatively	O
small	O
percentage	O
of	O
the	O
overall	O
message	O
.	O
</s>
<s>
In	O
financial	O
messaging	O
SOAP	B-Protocol
was	O
found	O
to	O
result	O
in	O
a	O
24	O
times	O
larger	O
message	O
than	O
previous	O
protocols	O
FIX	B-Protocol
(	O
Financial	B-Protocol
Information	I-Protocol
Exchange	I-Protocol
)	O
and	O
CDR	B-Protocol
(	O
Common	B-Protocol
Data	I-Protocol
Representation	I-Protocol
)	O
.	O
</s>
<s>
XML	B-Protocol
Information	O
Set	O
does	O
not	O
have	O
to	O
be	O
serialized	B-Application
in	O
XML	B-Protocol
.	O
</s>
<s>
For	O
instance	O
,	O
CSV	O
and	O
JSON	B-General_Concept
XML-infoset	O
representations	O
exist	O
.	O
</s>
<s>
The	O
concept	O
of	O
SOAP	B-Protocol
bindings	O
allows	O
for	O
specific	O
bindings	O
for	O
a	O
specific	O
application	O
.	O
</s>
<s>
SOAP	B-Protocol
's	O
neutrality	O
characteristic	O
explicitly	O
makes	O
it	O
suitable	O
for	O
use	O
with	O
any	O
transport	O
protocol	O
.	O
</s>
<s>
Implementations	O
often	O
use	O
HTTP	B-Protocol
as	O
a	O
transport	O
protocol	O
,	O
but	O
other	O
popular	O
transport	O
protocols	O
can	O
be	O
used	O
.	O
</s>
<s>
For	O
example	O
,	O
SOAP	B-Protocol
can	O
also	O
be	O
used	O
over	O
SMTP	B-Protocol
,	O
JMS	B-Language
and	O
message	B-Operating_System
queues	I-Operating_System
.	O
</s>
<s>
SOAP	B-Protocol
,	O
when	O
combined	O
with	O
HTTP	B-Protocol
post/response	O
exchanges	O
,	O
tunnels	O
easily	O
through	O
existing	O
firewalls	B-Application
and	O
proxies	O
,	O
and	O
consequently	O
does	O
n't	O
require	O
modifying	O
the	O
widespread	O
computing	O
and	O
communication	O
infrastructures	O
that	O
exist	O
for	O
processing	O
HTTP	B-Protocol
post/response	O
exchanges	O
.	O
</s>
<s>
SOAP	B-Protocol
has	O
available	O
to	O
it	O
all	O
the	O
facilities	O
of	O
XML	B-Protocol
,	O
including	O
easy	O
internationalization	O
and	O
extensibility	O
with	O
XML	B-Protocol
Namespaces	O
.	O
</s>
<s>
When	O
using	O
standard	O
implementation	O
and	O
the	O
default	O
SOAP/HTTP	O
binding	O
,	O
the	O
XML	B-Protocol
infoset	O
is	O
serialized	B-Application
as	O
XML	B-Protocol
.	O
</s>
<s>
To	O
improve	O
performance	O
for	O
the	O
special	O
case	O
of	O
XML	B-Protocol
with	O
embedded	O
binary	O
objects	O
,	O
the	O
Message	O
Transmission	O
Optimization	O
Mechanism	O
was	O
introduced	O
.	O
</s>
<s>
When	O
relying	O
on	O
HTTP	B-Protocol
as	O
a	O
transport	O
protocol	O
and	O
not	O
using	O
Web	O
Services	O
Addressing	O
or	O
an	O
Enterprise	B-Application
Service	I-Application
Bus	I-Application
,	O
the	O
roles	O
of	O
the	O
interacting	O
parties	O
are	O
fixed	O
.	O
</s>
<s>
SOAP	B-Protocol
is	O
less	O
"	O
simple	O
"	O
than	O
the	O
name	O
would	O
suggest	O
.	O
</s>
<s>
The	O
verbosity	O
of	O
the	O
protocol	O
,	O
slow	O
parsing	O
speed	O
of	O
XML	B-Protocol
,	O
and	O
lack	O
of	O
a	O
standardized	O
interaction	O
model	O
led	O
to	O
the	O
dominance	O
of	O
services	O
using	O
the	O
HTTP	B-Protocol
protocol	I-Protocol
more	O
directly	O
.	O
</s>
<s>
See	O
,	O
for	O
example	O
,	O
REST	B-Protocol
.	O
</s>
<s>
Being	O
protocol-agnostic	O
,	O
SOAP	B-Protocol
is	O
unable	O
to	O
take	O
advantage	O
of	O
protocol-specific	O
features	O
and	O
optimizations	O
such	O
as	O
REST	B-Protocol
's	O
Uniform	O
Interface	O
or	O
caching	B-Protocol
–	O
instead	O
having	O
to	O
reimplement	O
them	O
(	O
as	O
with	O
WS-Addressing	O
)	O
.	O
</s>
