<s>
In	O
software	O
development	O
XRX	B-Application
is	O
a	O
web	O
application	O
architecture	O
based	O
on	O
XForms	B-Application
,	O
REST	B-Protocol
and	O
XQuery	B-Language
.	O
</s>
<s>
XRX	B-Application
applications	O
store	O
data	O
on	O
both	O
the	O
web	B-Application
client	I-Application
and	O
on	O
the	O
web	B-Application
server	I-Application
in	O
XML	B-Protocol
format	O
and	O
do	O
not	O
require	O
a	O
translation	O
between	O
data	O
formats	O
.	O
</s>
<s>
XRX	B-Application
is	O
considered	O
a	O
simple	O
and	O
elegant	O
application	O
architecture	O
due	O
to	O
the	O
minimal	O
number	O
of	O
translations	O
needed	O
to	O
transport	O
data	O
between	O
client	O
and	O
server	O
systems	O
.	O
</s>
<s>
The	O
XRX	B-Application
architecture	O
is	O
also	O
tightly	O
coupled	O
to	O
W3C	O
standards	O
(	O
CSS	B-Language
,	O
XHTML	O
2.0	O
,	O
XPath	B-Language
,	O
XML	B-Protocol
Schema	O
)	O
to	O
ensure	O
XRX	B-Application
applications	O
will	O
be	O
robust	O
in	O
the	O
future	O
.	O
</s>
<s>
Because	O
XRX	B-Application
applications	O
leverage	O
modern	O
declarative	B-Language
languages	I-Language
on	O
the	O
client	O
and	O
functional	B-Language
languages	I-Language
on	O
the	O
server	O
they	O
are	O
designed	O
to	O
empower	O
non-developers	O
who	O
are	O
not	O
familiar	O
with	O
traditional	O
imperative	B-Application
languages	I-Application
such	O
as	O
JavaScript	B-Language
,	O
Java	B-Language
or	O
.Net	B-Application
.	I-Application
</s>
<s>
XRX	B-Application
is	O
a	O
zero	O
translation	O
application	O
architecture	O
that	O
uses	O
XML	B-Protocol
to	O
store	O
data	O
in	O
the	O
client	O
web	B-Application
browser	I-Application
,	O
on	O
the	O
application	O
server	O
and	O
in	O
the	O
database	O
server	O
.	O
</s>
<s>
It	O
is	O
because	O
each	O
of	O
these	O
layers	O
use	O
XML	B-Protocol
as	O
the	O
same	O
structural	O
data	O
model	O
that	O
XRX	B-Application
applications	O
do	O
not	O
have	O
to	O
translate	O
data	O
structures	O
to	O
and	O
from	O
both	O
object	O
and	O
relational	O
data	O
structures	O
.	O
</s>
<s>
Because	O
of	O
the	O
lack	O
of	O
need	O
for	O
translation	O
,	O
XRX	B-Application
is	O
considered	O
to	O
have	O
a	O
clean	O
and	O
elegant	O
design	O
.	O
</s>
<s>
The	O
XRX	B-Application
web	O
application	O
architecture	O
allows	O
developers	O
to	O
focus	O
on	O
the	O
business	O
problem	O
and	O
not	O
the	O
translation	O
problem	O
.	O
</s>
<s>
XRX	B-Application
benefits	O
from	O
several	O
advances	O
in	O
software	O
technology	O
:	O
</s>
<s>
This	O
replaces	O
much	O
of	O
the	O
JavaScript	B-Language
code	O
required	O
in	O
most	O
AJAX	O
applications	O
.	O
</s>
<s>
An	O
advanced	O
event	O
model	O
(	O
XML	B-Language
Events	I-Language
)	O
consistent	O
with	O
W3C	O
standards	O
that	O
frees	O
applications	O
from	O
having	O
to	O
deal	O
with	O
vendor-specific	O
and	O
browser-specific	O
event	O
handling	O
.	O
</s>
<s>
A	O
declarative	B-Language
programming	I-Language
style	O
that	O
allows	O
most	O
client	O
XForms	B-Application
applications	O
to	O
be	O
created	O
using	O
a	O
small	O
set	O
of	O
approximately	O
20	O
elements	O
.	O
</s>
<s>
This	O
allows	O
rich	O
client	O
applications	O
to	O
be	O
created	O
without	O
knowledge	O
of	O
JavaScript	B-Language
or	O
other	O
procedural	O
scripting	O
languages	O
.	O
</s>
<s>
An	O
easy-to-extend	O
system	O
for	O
creating	O
new	O
user	O
interface	O
controls	O
using	O
the	O
EXtensible	B-Application
Bindings	I-Application
Language	I-Application
.	O
</s>
<s>
Many	O
native	O
XML	B-Protocol
databases	O
have	O
built-in	O
REST	B-Protocol
interfaces	I-Protocol
making	O
each	O
XQuery	B-Language
inherently	O
a	O
RESTful	B-Protocol
web	I-Protocol
service	I-Protocol
.	O
</s>
<s>
A	O
functional	B-Language
programming	I-Language
model	O
that	O
promotes	O
side-effect	O
free	O
systems	O
that	O
are	O
easier	O
to	O
debug	O
and	O
easier	O
to	O
run	O
on	O
multiple	O
processors	O
.	O
</s>
<s>
An	O
easy-to-extend	O
system	O
using	O
XQuery	B-Language
function	O
and	O
modules	O
.	O
</s>
<s>
One	O
of	O
the	O
principal	O
benefits	O
of	O
the	O
XRX	B-Application
architecture	O
is	O
that	O
it	O
avoids	O
the	O
requirement	O
to	O
"	O
shred	O
"	O
complex	O
data	O
structures	O
into	O
relational	O
structures	O
and	O
then	O
reconstitute	O
the	O
data	O
back	O
into	O
structures	O
when	O
a	O
record	O
is	O
edited	O
on	O
the	O
client	O
.	O
</s>
<s>
Another	O
benefits	O
of	O
the	O
XRX	B-Application
Web	O
application	O
architecture	O
is	O
that	O
it	O
avoids	O
most	O
of	O
the	O
problems	O
around	O
the	O
object-relational	B-Architecture
impedance	I-Architecture
mismatch	I-Architecture
.	O
</s>
<s>
Another	O
advantage	O
is	O
that	O
the	O
client	O
developer	O
does	O
not	O
have	O
to	O
learn	O
JavaScript	B-Language
on	O
the	O
client	O
.	O
</s>
<s>
Many	O
traditional	O
web	O
application	O
architectures	O
created	O
in	O
the	O
late	O
1990	O
were	O
based	O
on	O
middle	O
object	O
tiers	O
and	O
persistence	O
layers	O
that	O
used	O
tabular	O
data	O
streams	O
and	O
relational	B-Application
database	I-Application
systems	O
.	O
</s>
<s>
His	O
presentation	O
was	O
one	O
of	O
the	O
first	O
to	O
specifically	O
suggest	O
that	O
the	O
combination	O
of	O
three	O
technologies	O
:	O
XForms	B-Application
and	O
XQuery	B-Language
with	O
REST	B-Protocol
interfaces	I-Protocol
would	O
have	O
surprisingly	O
beneficial	O
effects	O
.	O
</s>
<s>
In	O
his	O
presentation	O
"	O
XForms	B-Application
and	O
the	O
eXist	O
XML	B-Protocol
database	O
:	O
a	O
perfect	O
couple	O
"	O
,	O
Bruchez	O
showed	O
that	O
many	O
people	O
were	O
discovering	O
synergistic	O
benefits	O
of	O
XForms	B-Application
on	O
the	O
client	O
and	O
XQuery	B-Language
on	O
the	O
server	O
.	O
</s>
<s>
The	O
label	O
for	O
XRX	B-Application
was	O
suggested	O
by	O
a	O
blog	O
posting	O
by	O
Dan	O
McCreary	O
on	O
December	O
14	O
,	O
2007	O
.	O
</s>
<s>
It	O
was	O
in	O
this	O
article	O
that	O
Dan	O
suggested	O
the	O
need	O
for	O
a	O
contagious	O
meme	O
for	O
the	O
ideas	O
behind	O
the	O
XRX	B-Application
architecture	O
.	O
</s>
<s>
Although	O
XRX	B-Application
was	O
originally	O
intended	O
to	O
connote	O
the	O
use	O
of	O
XForms	B-Application
on	O
the	O
client	O
,	O
REST	B-Protocol
as	O
an	O
interface	O
and	O
XQuery	B-Language
on	O
the	O
server	O
,	O
other	O
proponents	O
of	O
the	O
symmetrical	O
use	O
of	O
XML	B-Protocol
on	O
the	O
client	O
and	O
server	O
have	O
generalized	O
the	O
term	O
to	O
encompass	O
any	O
XML-centric	O
web	B-Application
client	I-Application
and	O
any	O
server	O
that	O
can	O
store	O
and	O
query	O
XML	B-Protocol
documents	I-Protocol
.	O
</s>
<s>
This	O
use	O
of	O
XRX	B-Application
is	O
generally	O
referred	O
to	O
as	O
"	O
shallow	O
XRX	B-Application
"	O
.	O
</s>
<s>
These	O
generalizations	O
do	O
benefit	O
from	O
a	O
simplified	O
zero-translation	O
architecture	O
but	O
many	O
do	O
not	O
benefit	O
from	O
REST	B-Protocol
interfaces	I-Protocol
,	O
XPath	B-Language
for	O
consistent	O
data	O
selection	O
,	O
declarative	B-Language
systems	O
in	O
the	O
client	O
,	O
and	O
functional	B-Language
languages	I-Language
on	O
the	O
server	O
(	O
one	O
of	O
the	O
key	O
aspects	O
of	O
XRX	B-Application
)	O
.	O
</s>
<s>
Use	O
of	O
all	O
three	O
technologies	O
(	O
XForms	B-Application
,	O
REST	B-Protocol
and	O
XQuery	B-Language
)	O
is	O
referred	O
to	O
as	O
"	O
deep	O
XRX	B-Application
"	O
.	O
</s>
<s>
Although	O
XRX	B-Application
architecture	O
is	O
centred	O
on	O
XForms	B-Application
and	O
XQuery	B-Language
,	O
it	O
does	O
not	O
preclude	O
the	O
use	O
of	O
other	O
technologies	O
that	O
manipulate	O
XML	B-Protocol
natively	O
,	O
such	O
as	O
XSLT	B-Application
,	O
XProc	B-Language
,	O
and	O
XSL-FO	B-Language
.	O
</s>
