<s>
A	O
web	B-Application
framework	I-Application
(	O
WF	O
)	O
or	O
web	B-Application
application	I-Application
framework	I-Application
(	O
WAF	O
)	O
is	O
a	O
software	B-Architecture
framework	I-Architecture
that	O
is	O
designed	O
to	O
support	O
the	O
development	O
of	O
web	B-Application
applications	I-Application
including	O
web	O
services	O
,	O
web	O
resources	O
,	O
and	O
web	B-General_Concept
APIs	I-General_Concept
.	O
</s>
<s>
Web	B-Application
frameworks	I-Application
provide	O
a	O
standard	O
way	O
to	O
build	O
and	O
deploy	O
web	B-Application
applications	I-Application
on	O
the	O
World	O
Wide	O
Web	O
.	O
</s>
<s>
Web	B-Application
frameworks	I-Application
aim	O
to	O
automate	O
the	O
overhead	O
associated	O
with	O
common	O
activities	O
performed	O
in	O
web	O
development	O
.	O
</s>
<s>
For	O
example	O
,	O
many	O
web	B-Application
frameworks	I-Application
provide	O
libraries	B-Library
for	O
database	O
access	O
,	O
templating	B-Language
frameworks	O
,	O
and	O
session	B-Protocol
management	I-Protocol
,	O
and	O
they	O
often	O
promote	O
code	O
reuse	O
.	O
</s>
<s>
As	O
the	O
design	O
of	O
the	O
World	O
Wide	O
Web	O
was	O
not	O
inherently	O
dynamic	O
,	O
early	O
hypertext	O
consisted	O
of	O
hand-coded	O
HTML	B-Language
text	O
files	O
that	O
were	O
published	O
on	O
web	B-Application
servers	I-Application
.	O
</s>
<s>
In	O
1993	O
,	O
the	O
Common	B-Language
Gateway	I-Language
Interface	I-Language
(	O
CGI	O
)	O
standard	O
was	O
introduced	O
for	O
interfacing	O
external	O
applications	O
with	O
web	B-Application
servers	I-Application
,	O
to	O
provide	O
a	O
dynamic	O
web	O
page	O
that	O
reflected	O
user	O
inputs	O
.	O
</s>
<s>
Original	O
implementations	O
of	O
the	O
CGI	O
interface	O
typically	O
had	O
adverse	O
effects	O
on	O
the	O
server	B-Application
load	B-Operating_System
however	O
,	O
because	O
each	O
request	O
started	O
a	O
separate	O
process	B-Operating_System
.	O
</s>
<s>
More	O
recent	O
implementations	O
utilize	O
persistent	O
processes	O
amongst	O
other	O
techniques	O
to	O
reduce	O
the	O
footprint	O
in	O
the	O
server	B-Application
's	O
resources	O
and	O
offer	O
a	O
general	O
performance	O
boost	O
.	O
</s>
<s>
In	O
1995	O
,	O
fully	O
integrated	O
server/language	O
development	O
environments	O
first	O
emerged	O
and	O
new	O
web-specific	O
languages	O
were	O
introduced	O
,	O
such	O
as	O
ColdFusion	B-Language
,	O
PHP	B-Application
,	O
and	O
Active	B-General_Concept
Server	I-General_Concept
Pages	I-General_Concept
.	O
</s>
<s>
Although	O
the	O
vast	O
majority	O
of	O
languages	O
for	O
creating	O
dynamic	O
web	O
pages	O
have	O
libraries	B-Library
to	O
help	O
with	O
common	O
tasks	O
,	O
web	B-Application
applications	I-Application
often	O
require	O
specific	O
libraries	B-Library
for	O
particular	O
tasks	O
,	O
such	O
as	O
creating	O
HTML	B-Language
(	O
for	O
example	O
,	O
Jakarta	B-Language
Server	I-Language
Faces	I-Language
)	O
.	O
</s>
<s>
In	O
the	O
late	O
1990s	O
,	O
mature	O
,	O
"	O
full	O
stack	O
"	O
frameworks	O
began	O
to	O
appear	O
,	O
that	O
often	O
gathered	O
multiple	O
libraries	B-Library
useful	O
for	O
web	O
development	O
into	O
a	O
single	O
cohesive	O
software	B-Application
stack	I-Application
for	O
web	O
developers	O
to	O
use	O
.	O
</s>
<s>
Examples	O
of	O
this	O
include	O
ASP.NET	B-Application
,	O
Java	B-Language
EE	I-Language
,	O
WebObjects	B-Language
,	O
web2py	B-Application
,	O
OpenACS	B-Protocol
,	O
Catalyst	B-Language
,	O
Mojolicious	B-Language
,	O
Ruby	B-Application
on	I-Application
Rails	I-Application
,	O
Laravel	B-Language
,	O
Grails	B-Language
,	O
Django	B-Language
,	O
Zend	B-Language
Framework	I-Language
,	O
Sails.js	B-Language
,	O
Yii	B-Language
,	O
CakePHP	B-Language
,	O
and	O
Symfony	B-Language
.	O
</s>
<s>
Most	O
web	B-Application
frameworks	I-Application
are	O
based	O
on	O
the	O
model	O
–	O
view	O
–	O
controller	O
(	O
MVC	O
)	O
pattern	O
.	O
</s>
<s>
Many	O
frameworks	O
follow	O
the	O
MVC	O
architectural	O
pattern	O
to	O
separate	O
the	O
data	B-Application
model	I-Application
into	O
business	O
rules	O
(	O
the	O
"	O
controller	O
"	O
)	O
and	O
the	O
user	B-Application
interface	I-Application
(	O
the	O
"	O
view	O
"	O
)	O
.	O
</s>
<s>
In	O
web	B-Application
applications	I-Application
,	O
this	O
permits	O
different	O
views	O
to	O
be	O
presented	O
,	O
for	O
example	O
serving	O
different	O
web	O
pages	O
for	O
mobile	O
vs.	O
desktop	O
browsers	O
,	O
or	O
providing	O
machine-readable	O
web	O
service	O
interfaces	O
.	O
</s>
<s>
Django	B-Language
,	O
Ruby	B-Application
on	I-Application
Rails	I-Application
,	O
Symfony	B-Language
,	O
Spring	B-Application
MVC	I-Application
,	O
Stripes	B-Language
,	O
Sails.js	B-Language
,	O
CodeIgniter	B-Language
are	O
good	O
examples	O
of	O
this	O
architecture	O
.	O
</s>
<s>
Lift	B-Language
,	O
Tapestry	B-Language
,	O
JBoss	B-Operating_System
Seam	I-Operating_System
,	O
Jakarta	B-Language
Server	I-Language
Faces	I-Language
,	O
and	O
Wicket	B-Language
are	O
examples	O
of	O
pull-based	O
architectures	O
.	O
</s>
<s>
Play	B-Language
,	O
Struts	B-Language
,	O
RIFE	O
,	O
and	O
ZK	B-Language
have	O
support	O
for	O
both	O
push	O
-	O
and	O
pull-based	O
application	O
controller	O
calls	O
.	O
</s>
<s>
In	O
three-tier	B-Operating_System
organization	I-Operating_System
,	O
applications	O
are	O
structured	O
around	O
three	O
physical	O
tiers	B-Operating_System
:	O
client	O
,	O
application	O
,	O
and	O
database	O
.	O
</s>
<s>
The	O
database	O
is	O
normally	O
an	O
RDBMS	B-Application
.	O
</s>
<s>
The	O
application	O
contains	O
the	O
business	O
logic	O
,	O
running	O
on	O
a	O
server	B-Application
and	O
communicates	O
with	O
the	O
client	O
using	O
HTTP	B-Protocol
.	I-Protocol
</s>
<s>
The	O
client	O
on	O
web	B-Application
applications	I-Application
is	O
a	O
web	O
browser	O
that	O
runs	O
HTML	B-Language
generated	O
by	O
the	O
application	O
layer	O
.	O
</s>
<s>
The	O
term	O
should	O
not	O
be	O
confused	O
with	O
MVC	O
,	O
where	O
,	O
unlike	O
in	O
three-tier	B-Operating_System
architecture	I-Operating_System
,	O
it	O
is	O
considered	O
a	O
good	O
practice	O
to	O
keep	O
business	O
logic	O
away	O
from	O
the	O
controller	O
,	O
the	O
"	O
middle	O
layer	O
"	O
.	O
</s>
<s>
Frameworks	O
are	O
built	O
to	O
support	O
the	O
construction	O
of	O
internet	B-Application
applications	I-Application
based	O
on	O
a	O
single	O
programming	O
language	O
,	O
ranging	O
in	O
focus	O
from	O
general	O
purpose	O
tools	O
such	O
as	O
Zend	B-Language
Framework	I-Language
and	O
Ruby	B-Application
on	I-Application
Rails	I-Application
,	O
which	O
augment	O
the	O
capabilities	O
of	O
a	O
specific	O
language	O
,	O
to	O
native-language	O
programmable	O
packages	O
built	O
around	O
a	O
specific	O
user	O
application	O
,	O
such	O
as	O
content	B-Protocol
management	I-Protocol
systems	I-Protocol
(	O
CMS	O
)	O
,	O
some	O
mobile	O
development	O
tools	O
and	O
some	O
portal	O
tools	O
.	O
</s>
<s>
Web	B-Application
frameworks	I-Application
must	O
function	O
according	O
to	O
the	O
architectural	O
rules	O
of	O
browsers	O
and	O
protocols	O
such	O
as	O
HTTP	B-Protocol
,	O
which	O
is	O
stateless	B-Protocol
.	O
</s>
<s>
Webpages	O
are	O
served	O
up	O
by	O
a	O
server	B-Application
and	O
can	O
then	O
be	O
modified	O
by	O
the	O
browser	O
using	O
JavaScript	B-Language
.	O
</s>
<s>
Server-side	O
page	O
changes	O
typically	O
require	O
that	O
the	O
page	O
be	O
refreshed	O
,	O
but	O
allow	O
any	O
language	O
to	O
be	O
used	O
and	O
more	O
computing	O
power	O
to	O
be	O
utilized	O
.	O
</s>
<s>
Client-side	O
changes	O
allow	O
the	O
page	O
to	O
be	O
updated	O
in	O
small	O
chunks	O
which	O
feels	O
like	O
a	O
desktop	O
application	O
,	O
but	O
are	O
limited	O
to	O
JavaScript	B-Language
and	O
run	O
in	O
the	O
user	O
's	O
browser	O
,	O
which	O
may	O
have	O
limited	O
computing	O
power	O
.	O
</s>
<s>
Applications	O
which	O
make	O
heavy	O
use	O
of	O
JavaScript	B-Language
and	O
only	O
refresh	O
parts	O
of	O
the	O
page	O
,	O
are	O
called	O
single-page	B-Application
applications	I-Application
and	O
typically	O
make	O
use	O
of	O
a	O
client-side	O
JavaScript	B-Language
web	B-Application
framework	I-Application
to	O
organize	O
the	O
code	O
.	O
</s>
<s>
Examples	O
include	O
Backbone.js	B-Language
,	O
AngularJS	B-Application
,	O
Angular	B-Language
,	O
EmberJS	B-Language
,	O
ReactJS	B-Application
,	O
jQuery	B-Language
UI	I-Language
,	O
Svelte	B-Language
,	O
and	O
Vue.js	B-Language
.	O
</s>
<s>
This	O
"	O
inversion	B-Language
of	I-Language
control	I-Language
"	O
design	O
pattern	O
is	O
considered	O
to	O
be	O
a	O
defining	O
principle	O
of	O
a	O
framework	O
,	O
and	O
benefits	O
the	O
code	O
by	O
enforcing	O
a	O
common	O
flow	O
for	O
a	O
team	O
which	O
everyone	O
can	O
customize	O
in	O
similar	O
ways	O
.	O
</s>
<s>
For	O
example	O
,	O
some	O
popular	O
"	O
microframeworks	O
"	O
such	O
as	O
Ruby	O
's	O
Sinatra	B-Application
(	O
which	O
inspired	O
Express.js	B-Language
)	O
allow	O
for	O
"	O
middleware	O
"	O
hooks	O
prior	O
to	O
and	O
after	O
HTTP	B-Protocol
requests	I-Protocol
.	O
</s>
<s>
These	O
middleware	O
functions	O
can	O
be	O
anything	O
,	O
and	O
allow	O
the	O
user	O
to	O
define	O
logging	O
,	O
authentication	O
and	O
session	B-Protocol
management	I-Protocol
,	O
and	O
redirecting	O
.	O
</s>
<s>
Web	B-Protocol
caching	I-Protocol
is	O
the	O
caching	B-Protocol
of	O
web	O
documents	B-Protocol
in	O
order	O
to	O
reduce	O
bandwidth	O
usage	O
,	O
server	B-Application
load	B-Operating_System
,	O
and	O
perceived	O
"	O
lag	O
"	O
.	O
</s>
<s>
A	O
web	B-Protocol
cache	I-Protocol
stores	O
copies	O
of	O
documents	B-Protocol
passing	O
through	O
it	O
;	O
subsequent	O
requests	O
may	O
be	O
satisfied	O
from	O
the	O
cache	O
if	O
certain	O
conditions	O
are	O
met	O
.	O
</s>
<s>
Some	O
application	B-Application
frameworks	I-Application
provide	O
mechanisms	O
for	O
caching	B-Protocol
documents	B-Protocol
and	O
bypassing	O
various	O
stages	O
of	O
the	O
page	O
's	O
preparation	O
,	O
such	O
as	O
database	O
access	O
or	O
template	B-Language
interpretation	O
.	O
</s>
<s>
Some	O
web	B-Application
frameworks	I-Application
come	O
with	O
authentication	O
and	O
authorization	O
frameworks	O
,	O
that	O
enable	O
the	O
web	B-Application
server	I-Application
to	O
identify	O
the	O
users	O
of	O
the	O
application	O
,	O
and	O
restrict	O
access	O
to	O
functions	O
based	O
on	O
some	O
defined	O
criteria	O
.	O
</s>
<s>
Drupal	B-Application
is	O
one	O
example	O
that	O
provides	O
role-based	O
access	O
to	O
pages	O
,	O
and	O
provides	O
a	O
web-based	B-Application
interface	O
for	O
creating	O
users	O
and	O
assigning	O
them	O
roles	O
.	O
</s>
<s>
Many	O
web	B-Application
frameworks	I-Application
create	O
a	O
unified	O
API	B-General_Concept
to	O
a	O
database	O
backend	O
,	O
enabling	O
web	B-Application
applications	I-Application
to	O
work	O
with	O
a	O
variety	O
of	O
databases	O
with	O
no	O
code	O
changes	O
,	O
and	O
allowing	O
programmers	O
to	O
work	O
with	O
higher-level	O
concepts	O
.	O
</s>
<s>
Additionally	O
,	O
some	O
object-oriented	B-Language
frameworks	O
contain	O
mapping	O
tools	O
to	O
provide	O
object-relational	B-General_Concept
mapping	I-General_Concept
,	O
which	O
maps	O
objects	B-Language
to	O
tuples	B-Application
.	O
</s>
<s>
Some	O
frameworks	O
minimize	O
web	B-Application
application	I-Application
configuration	O
through	O
the	O
use	O
of	O
introspection	B-Application
and/or	O
following	O
well-known	O
conventions	O
.	O
</s>
<s>
For	O
example	O
,	O
many	O
Java	O
frameworks	O
use	O
Hibernate	B-Library
as	O
a	O
persistence	O
layer	O
,	O
which	O
can	O
generate	O
a	O
database	O
schema	O
at	O
runtime	O
capable	O
of	O
persisting	O
the	O
necessary	O
information	O
.	O
</s>
<s>
This	O
allows	O
the	O
application	O
designer	O
to	O
design	O
business	O
objects	B-Language
without	O
needing	O
to	O
explicitly	O
define	O
a	O
database	O
schema	O
.	O
</s>
<s>
Frameworks	O
such	O
as	O
Ruby	B-Application
on	I-Application
Rails	I-Application
can	O
also	O
work	O
in	O
reverse	O
,	O
that	O
is	O
,	O
define	O
properties	O
of	O
model	O
objects	B-Language
at	O
runtime	O
based	O
on	O
a	O
database	O
schema	O
.	O
</s>
<s>
Other	O
features	O
web	B-Application
frameworks	I-Application
may	O
provide	O
include	O
transactional	B-General_Concept
support	I-General_Concept
and	O
database	B-General_Concept
migration	I-General_Concept
tools	I-General_Concept
.	O
</s>
<s>
Some	O
frameworks	O
,	O
such	O
as	O
Drupal	B-Application
and	O
Django	B-Language
,	O
match	O
the	O
provided	O
URL	O
against	O
pre-determined	O
patterns	O
using	O
regular	B-Language
expressions	I-Language
,	O
while	O
some	O
others	O
use	O
rewriting	O
techniques	O
to	O
translate	O
the	O
provided	O
URL	O
into	O
one	O
that	O
the	O
underlying	O
engine	O
will	O
recognize	O
.	O
</s>
<s>
Another	O
technique	O
is	O
that	O
of	O
graph	B-Algorithm
traversal	I-Algorithm
such	O
as	O
used	O
by	O
Zope	B-Language
,	O
where	O
a	O
URL	O
is	O
decomposed	O
in	O
steps	O
that	O
traverse	O
an	O
object	O
graph	O
(	O
of	O
models	O
and	O
views	O
)	O
.	O
</s>
<s>
A	O
URL	O
mapping	O
system	O
that	O
uses	O
pattern	O
matching	O
or	O
rewriting	O
to	O
route	O
and	O
handle	O
requests	O
allows	O
for	O
shorter	O
more	O
"	O
friendly	B-Protocol
URLs	I-Protocol
"	O
to	O
be	O
used	O
,	O
increasing	O
the	O
simplicity	O
of	O
the	O
site	O
and	O
allowing	O
for	O
better	O
indexing	O
by	O
search	O
engines	O
.	O
</s>
<s>
A	O
graph	B-Algorithm
traversal	I-Algorithm
approach	O
also	O
tends	O
to	O
result	O
in	O
the	O
creation	O
of	O
friendly	B-Protocol
URLs	I-Protocol
.	O
</s>
<s>
Ajax	B-General_Concept
,	O
shorthand	O
for	O
"	O
Asynchronous	B-General_Concept
JavaScript	I-General_Concept
and	I-General_Concept
XML	I-General_Concept
"	O
,	O
is	O
a	O
web	O
development	O
technique	O
for	O
creating	O
web	B-Application
applications	I-Application
.	O
</s>
<s>
The	O
intent	O
is	O
to	O
make	O
web	O
pages	O
feel	O
more	O
responsive	O
by	O
exchanging	O
small	O
amounts	O
of	O
data	O
with	O
the	O
server	B-Application
behind	O
the	O
scenes	O
,	O
so	O
that	O
the	O
entire	O
web	O
page	O
does	O
not	O
have	O
to	O
be	O
reloaded	O
each	O
time	O
the	O
user	O
requests	O
a	O
change	O
.	O
</s>
<s>
This	O
is	O
intended	O
to	O
increase	O
a	O
web	O
page	O
's	O
interactivity	O
,	O
speed	O
,	O
maintainability	O
,	O
and	O
usability	B-General_Concept
.	O
</s>
<s>
Due	O
to	O
the	O
complexity	O
of	O
Ajax	B-General_Concept
programming	I-General_Concept
in	O
JavaScript	B-Language
,	O
there	O
are	O
numerous	O
Ajax	B-General_Concept
frameworks	I-General_Concept
that	O
exclusively	O
deal	O
with	O
Ajax	B-General_Concept
support	O
.	O
</s>
<s>
Some	O
Ajax	B-General_Concept
frameworks	I-General_Concept
are	O
even	O
embedded	O
as	O
a	O
part	O
of	O
larger	O
frameworks	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
jQuery	B-Language
JavaScript	B-Language
library	I-Language
is	O
included	O
in	O
Ruby	B-Application
on	I-Application
Rails	I-Application
.	O
</s>
<s>
With	O
the	O
increased	O
interest	O
in	O
developing	O
"	O
Web	O
2.0	O
"	O
rich	B-Application
web	I-Application
applications	I-Application
,	O
the	O
complexity	O
of	O
programming	O
directly	O
in	O
Ajax	B-General_Concept
and	O
JavaScript	B-Language
has	O
become	O
so	O
apparent	O
that	O
compiler	O
technology	O
has	O
stepped	O
in	O
,	O
to	O
allow	O
developers	O
to	O
code	O
in	O
high-level	O
languages	O
such	O
as	O
Java	O
,	O
Python	O
and	O
Ruby	O
.	O
</s>
<s>
The	O
first	O
of	O
these	O
compilers	O
was	O
Morfik	O
followed	O
by	O
Google	B-Language
Web	I-Language
Toolkit	I-Language
,	O
with	O
ports	O
to	O
Python	O
and	O
Ruby	O
in	O
the	O
form	O
of	O
Pyjs	B-Language
and	O
RubyJS	O
following	O
some	O
time	O
after	O
.	O
</s>
<s>
These	O
compilers	O
and	O
their	O
associated	O
widget	O
set	O
libraries	B-Library
make	O
the	O
development	O
of	O
rich	O
media	O
Ajax	B-General_Concept
applications	O
much	O
more	O
akin	O
to	O
that	O
of	O
developing	O
desktop	O
applications	O
.	O
</s>
<s>
These	O
utilities	O
may	O
offer	O
similar	O
tools	O
as	O
the	O
rest	B-Protocol
of	O
the	O
web	B-Application
application	I-Application
.	O
</s>
<s>
A	O
number	O
of	O
newer	O
Web	O
2.0	O
RESTful	B-Protocol
frameworks	O
are	O
now	O
providing	O
resource-oriented	B-Architecture
architecture	I-Architecture
(	O
ROA	O
)	O
infrastructure	O
for	O
building	O
collections	O
of	O
resources	O
in	O
a	O
sort	O
of	O
Semantic	O
Web	O
ontology	O
,	O
based	O
on	O
concepts	O
from	O
Resource	O
Description	O
Framework	O
(	O
RDF	O
)	O
.	O
</s>
