<s>
Catalyst	B-Language
is	O
an	O
open	B-Application
source	I-Application
web	B-Application
application	I-Application
framework	I-Application
written	O
in	O
Perl	B-Language
,	O
that	O
closely	O
follows	O
the	O
model	O
–	O
view	O
–	O
controller	O
(	O
MVC	O
)	O
architecture	O
,	O
and	O
supports	O
a	O
number	O
of	O
experimental	O
web	O
patterns	O
.	O
</s>
<s>
It	O
is	O
written	O
using	O
Moose	B-Language
,	O
a	O
modern	O
object	O
system	O
for	O
Perl	B-Language
.	O
</s>
<s>
Its	O
design	O
is	O
heavily	O
inspired	O
by	O
frameworks	O
such	O
as	O
Ruby	B-Application
on	I-Application
Rails	I-Application
,	O
Maypole	O
,	O
and	O
Spring	B-Application
.	O
</s>
<s>
A	O
web	O
application	O
developer	O
would	O
use	O
Catalyst	B-Language
to	O
deal	O
with	O
code	O
common	O
to	O
all	O
web	O
applications	O
:	O
it	O
provides	O
interfaces	O
to	O
web	O
servers	O
and	O
receiving	O
page	O
requests	O
,	O
dispatching	O
these	O
into	O
developer-written	O
code	O
to	O
process	O
and	O
return	O
the	O
requests	O
,	O
and	O
provides	O
a	O
standardised	O
interface	O
for	O
data	O
models	O
,	O
authentication	O
,	O
session	O
management	O
and	O
other	O
common	O
web	O
application	O
elements	O
.	O
</s>
<s>
a	O
session	O
storing	O
in	O
shared	O
memory	O
versus	O
as	O
a	O
database	O
table	O
,	O
or	O
using	O
FastCGI	O
versus	O
operating	O
as	O
an	O
within	O
Apache	B-Application
's	O
mod_perl	O
)	O
by	O
changing	O
the	O
configuration	O
of	O
Catalyst	B-Language
to	O
use	O
a	O
different	O
plugin	O
without	O
altering	O
the	O
application	O
code	O
.	O
</s>
<s>
Catalyst	B-Language
is	O
primarily	O
distributed	O
through	O
the	O
CPAN	B-Language
,	O
which	O
is	O
the	O
official	O
distribution	O
channel	O
for	O
Perl	B-Language
libraries	O
and	O
applications	O
.	O
</s>
<s>
Maypole	O
was	O
one	O
of	O
the	O
first	O
web	B-Application
application	I-Application
frameworks	I-Application
for	O
the	O
Perl	B-Language
programming	I-Language
language	I-Language
that	O
was	O
based	O
on	O
the	O
MVC	O
pattern	O
;	O
its	O
principal	O
author	O
was	O
Simon	O
Cozens	O
.	O
</s>
<s>
Catalyst	B-Language
started	O
as	O
a	O
fork	B-Application
of	O
Maypole	O
,	O
intended	O
to	O
become	O
Maypole	O
3.0	O
.	O
</s>
<s>
Development	O
ceased	O
on	O
Maypole	O
,	O
however	O
,	O
with	O
its	O
most	O
recent	O
release	O
in	O
April	O
2008	O
,	O
and	O
Catalyst	B-Language
became	O
its	O
modern	O
supported	O
equivalent	O
.	O
</s>
<s>
The	O
first	O
development	O
release	O
of	O
Catalyst	B-Language
took	O
place	O
on	O
28	O
January	O
2005	O
.	O
</s>
<s>
The	O
first	O
official	O
version	O
was	O
placed	O
in	O
CPAN	B-Language
on	O
16	O
February	O
2005	O
.	O
</s>
<s>
As	O
of	O
June	O
2011	O
,	O
Catalyst	B-Language
had	O
201	O
registered	O
contributors	O
.	O
</s>
<s>
Catalyst	B-Language
is	O
based	O
on	O
a	O
"	O
do	O
n't	O
repeat	O
yourself	O
"	O
(	O
DRY	O
)	O
principle	O
,	O
which	O
means	O
that	O
definitions	O
should	O
only	O
have	O
to	O
be	O
made	O
once	O
.	O
</s>
<s>
Catalyst	B-Language
can	O
be	O
used	O
with	O
automatic	O
class	O
loading	O
from	O
the	O
database	O
through	O
one	O
of	O
the	O
many	O
loader	O
modules	O
,	O
thus	O
requiring	O
no	O
code	O
for	O
the	O
database	O
layer	O
.	O
</s>
<s>
Another	O
guiding	O
principle	O
of	O
Catalyst	B-Language
is	O
flexibility	O
.	O
</s>
<s>
Catalyst	B-Language
promotes	O
the	O
re-use	O
of	O
existing	O
Perl	B-Language
modules	O
that	O
already	O
handle	O
common	O
web	O
application	O
concerns	O
well	O
.	O
</s>
<s>
The	O
Model	O
part	O
is	O
handled	O
through	O
DBIx::Class	B-Language
,	O
Plucene	O
,	O
Net::LDAP	O
and	O
other	O
model	O
classes	O
.	O
</s>
<s>
The	O
View	O
layer	O
is	O
usually	O
handled	O
by	O
Template	B-Language
Toolkit	I-Language
,	O
Mason	O
,	O
or	O
HTML::Template	O
,	O
among	O
others	O
.	O
</s>
<s>
Large	O
chunks	O
of	O
Controller	O
functionality	O
can	O
usually	O
be	O
deferred	O
to	O
one	O
of	O
the	O
many	O
Catalyst	B-Language
plugins	O
(	O
e.g.	O
,	O
Catalyst::Plugin::FormValidator	O
,	O
Catalyst::Plugin::Prototype	O
,	O
Catalyst::Plugin::Account::AutoDiscovery	O
,	O
etc	O
.	O
</s>
<s>
Finally	O
,	O
Catalyst	B-Language
offers	O
a	O
set	O
of	O
helpers	O
to	O
simplify	O
flow	O
control	O
and	O
mapping	O
URLs	O
to	O
controller	O
methods	O
.	O
</s>
<s>
Catalyst	B-Language
has	O
a	O
large	O
selection	O
of	O
plugins	O
.	O
</s>
<s>
For	O
example	O
,	O
it	O
has	O
JavaScript	O
generation	O
for	O
Ajax	B-General_Concept
and	O
RIAs	O
using	O
the	O
Catalyst::Plugin::Prototype	O
module	O
(	O
prototype	B-Language
is	O
an	O
Ajax	B-General_Concept
framework	I-General_Concept
)	O
.	O
</s>
<s>
Catalyst	B-Language
can	O
also	O
be	O
used	O
with	O
other	O
Ajax	B-General_Concept
frameworks	I-General_Concept
such	O
as	O
jQuery	B-Language
or	O
YUI	B-Language
,	O
the	O
Yahoo	B-Application
!	I-Application
</s>
<s>
For	O
development	O
and	O
testing	O
,	O
Catalyst	B-Language
has	O
a	O
built-in	O
simple	O
HTTP	O
server	O
.	O
</s>
<s>
For	O
production	O
use	O
,	O
Apache	B-Application
,	O
lighttpd	B-Protocol
,	O
Hiawatha	B-Application
,	O
Cherokee	B-Language
or	O
Nginx	B-Operating_System
with	O
FastCGI	O
or	O
mod_perl	O
support	O
is	O
recommended	O
,	O
but	O
any	O
web	O
server	O
with	O
CGI	O
or	O
FastCGI	O
support	O
will	O
work	O
.	O
</s>
<s>
On	O
Apache	B-Application
,	O
mod_perl	O
can	O
help	O
with	O
performance	O
considerably	O
,	O
though	O
its	O
use	O
might	O
be	O
an	O
issue	O
because	O
it	O
can	O
be	O
unsafe	O
to	O
share	O
multiple	O
applications	O
under	O
mod_perl	O
.	O
</s>
<s>
Since	O
early	O
2008	O
,	O
Catalyst	B-Language
applications	O
can	O
also	O
be	O
deployed	O
using	O
the	O
HTTP::Prefork	O
engine	O
which	O
provides	O
for	O
the	O
deployment	O
of	O
high	O
performance	O
Catalyst	B-Language
applications	O
without	O
a	O
separate	O
web	O
server	O
.	O
</s>
<s>
Starting	O
with	O
the	O
release	O
of	O
Catalyst	B-Language
5.9	O
,	O
Catalyst	B-Language
also	O
outputs	O
to	O
the	O
PSGI	O
spec	O
thus	O
it	O
can	O
be	O
run	O
on	O
any	O
Plack	B-Language
server	I-Language
and	O
along	O
with	O
any	O
server	O
or	O
protocol	O
that	O
supports	O
the	O
PSGI	O
spec	O
,	O
including	O
Mongrel2	B-Application
.	O
</s>
<s>
Catalyst	B-Language
can	O
run	O
using	O
any	O
database	O
supported	O
by	O
Perl	B-Language
's	I-Language
DBI	I-Language
(	O
this	O
means	O
almost	O
anything	O
,	O
even	O
a	O
CSV	O
file	O
)	O
,	O
but	O
a	O
proper	O
RDBMS	O
or	O
ODBMS	B-Application
is	O
recommended	O
.	O
</s>
<s>
The	O
database	B-Application
access	I-Application
is	I-Application
entirely	I-Application
abstracted	I-Application
from	O
the	O
programmer	O
's	O
point	O
of	O
view	O
and	O
Catalyst	B-Language
,	O
through	O
one	O
of	O
its	O
model	O
classes	O
,	O
handles	O
access	O
to	O
all	O
databases	O
automatically	O
–	O
though	O
,	O
if	O
needed	O
,	O
using	O
direct	O
SQL	B-Language
queries	O
is	O
possible	O
.	O
</s>
<s>
This	O
enables	O
database-neutrality	O
,	O
application	O
portability	O
over	O
different	O
database	O
systems	O
,	O
and	O
usability	O
of	O
pre-existing	O
databases	O
for	O
Catalyst	B-Language
application	O
development	O
as	O
much	O
as	O
possible	O
,	O
though	O
due	O
to	O
different	O
feature	O
sets	O
of	O
the	O
RDBMSes	O
,	O
it	O
is	O
not	O
completely	O
guaranteed	O
by	O
the	O
framework	O
alone	O
.	O
</s>
<s>
Several	O
different	O
RDBMS	O
systems	O
are	O
supported	O
,	O
including	O
MySQL	B-Application
,	O
PostgreSQL	B-Application
,	O
SQLite	B-Language
,	O
IBM	B-Application
Db2	I-Application
,	O
Oracle	B-General_Concept
and	O
Microsoft	B-Application
SQL	I-Application
Server	I-Application
.	O
</s>
<s>
For	O
ODBMSes	O
,	O
there	O
is	O
explicit	O
support	O
for	O
KiokuDB	O
via	O
Catalyst::Model::KiokuDB	O
.	O
</s>
<s>
The	O
Model	O
abstraction	O
allows	O
databases	O
of	O
any	O
nature	O
to	O
be	O
accessed	O
via	O
Catalyst::Model::Adaptor	O
.	O
</s>
<s>
Many	O
Catalyst-based	O
projects	O
use	O
DBIx::Class	B-Language
as	O
the	O
ORM	B-General_Concept
layer	I-General_Concept
,	O
which	O
provides	O
further	O
abstraction	O
of	O
SQL	B-Language
queries	O
,	O
using	O
a	O
resultset-based	O
API	O
with	O
transparent	O
support	O
for	O
arbitrary	O
joins	O
and	O
other	O
features	O
.	O
</s>
<s>
Websites	O
powered	O
by	O
Catalyst	B-Language
include	O
Magazines.com,	O
bbc.co.uk	B-Application
iPlayer	I-Application
backend	O
,	O
DuckDuckGo	B-Application
's	I-Application
Community	O
Platform	O
,	O
and	O
Tripwolf.com	O
.	O
</s>
<s>
The	O
MojoMojo	B-Language
wiki	B-Protocol
engine	I-Protocol
is	O
written	O
using	O
Catalyst	B-Language
.	O
</s>
<s>
YouPorn	O
was	O
powered	O
by	O
Catalyst	B-Language
until	O
2012	O
.	O
</s>
