<s>
Platform	B-Application
as	I-Application
a	I-Application
service	I-Application
(	O
PaaS	B-Application
)	O
or	O
application	B-Application
platform	I-Application
as	I-Application
a	I-Application
service	I-Application
(	O
aPaaS	B-Application
)	O
or	O
platform-based	O
service	O
is	O
a	O
category	O
of	O
cloud	O
computing	O
services	O
that	O
allows	O
customers	O
to	O
provision	O
,	O
instantiate	O
,	O
run	O
,	O
and	O
manage	O
a	O
modular	O
bundle	O
comprising	O
a	O
computing	B-Device
platform	I-Device
and	O
one	O
or	O
more	O
applications	O
,	O
without	O
the	O
complexity	O
of	O
building	O
and	O
maintaining	O
the	O
infrastructure	O
typically	O
associated	O
with	O
developing	O
and	O
launching	O
the	O
application(s )	O
,	O
and	O
to	O
allow	O
developers	O
to	O
create	O
,	O
develop	O
,	O
and	O
package	O
such	O
software	O
bundles	O
.	O
</s>
<s>
PaaS	B-Application
can	O
be	O
delivered	O
in	O
three	O
ways	O
:	O
</s>
<s>
As	O
a	O
public	O
cloud	O
service	O
from	O
a	O
provider	O
,	O
where	O
the	O
consumer	O
controls	O
software	O
deployment	O
with	O
minimal	O
configuration	O
options	O
,	O
and	O
the	O
provider	O
provides	O
the	O
networks	O
,	O
servers	B-Application
,	O
storage	B-General_Concept
,	O
operating	B-General_Concept
system	I-General_Concept
(	O
OS	O
)	O
,	O
middleware	B-General_Concept
(	O
e.g.	O
</s>
<s>
Java	B-Language
runtime	I-Language
,	O
.NET	B-Application
runtime	B-Device
,	O
integration	O
,	O
etc	O
.	O
</s>
<s>
As	O
a	O
private	O
service	O
(	O
software	O
or	O
appliance	B-Application
)	O
behind	O
a	O
firewall	O
.	O
</s>
<s>
As	O
software	O
deployed	O
on	O
public	O
infrastructure	B-General_Concept
as	I-General_Concept
a	I-General_Concept
service	I-General_Concept
.	O
</s>
<s>
The	O
first	O
public	O
platform	B-Application
as	I-Application
a	I-Application
service	I-Application
was	O
Zimki	O
,	O
launched	O
by	O
Fotango	O
,	O
a	O
London-based	O
company	O
owned	O
by	O
Canon	O
Europe	O
.	O
</s>
<s>
It	O
had	O
demonstrated	O
the	O
technical	O
viability	O
of	O
Platform	B-Application
as	I-Application
a	I-Application
Service	I-Application
,	O
but	O
also	O
provided	O
the	O
first	O
example	O
of	O
the	O
perils	O
of	O
being	O
dependent	O
on	O
a	O
single	O
provider	O
.	O
</s>
<s>
This	O
was	O
highlighted	O
when	O
the	O
CEO	O
(	O
Simon	O
Wardley	O
,	O
known	O
for	O
Wardley	O
maps	O
)	O
announced	O
at	O
OSCON	O
2007	O
that	O
Zimki	O
would	O
no	O
longer	O
be	O
open-sourced	O
and	O
discussed	O
the	O
future	O
of	O
what	O
was	O
then	O
called	O
framework-as-a-service	O
(	O
later	O
called	O
platform-as-a-service	B-Application
)	O
covering	O
the	O
importance	O
of	O
a	O
market	O
of	O
providers	O
based	O
on	O
an	O
open-source	O
reference	O
model	O
.	O
</s>
<s>
The	O
original	O
intent	O
of	O
PaaS	B-Application
was	O
to	O
simplify	O
the	O
writing	O
of	O
code	O
,	O
with	O
the	O
infrastructure	O
and	O
operations	O
handled	O
by	O
the	O
PaaS	B-Application
provider	O
.	O
</s>
<s>
Because	O
many	O
companies	O
did	O
not	O
want	O
to	O
have	O
everything	O
in	O
the	O
public	O
cloud	O
,	O
private	O
and	O
hybrid	O
PaaS	B-Application
options	O
(	O
managed	O
by	O
internal	O
IT	O
departments	O
)	O
were	O
created	O
.	O
</s>
<s>
PaaS	B-Application
provides	O
an	O
environment	O
for	O
developers	O
and	O
companies	O
to	O
create	O
,	O
host	O
and	O
deploy	O
applications	O
,	O
saving	O
developers	O
from	O
the	O
complexities	O
of	O
infrastructure	O
(	O
setting	O
up	O
,	O
configuring	O
and	O
managing	O
elements	O
such	O
as	O
servers	B-Application
and	O
databases	O
)	O
.	O
</s>
<s>
PaaS	B-Application
can	O
improve	O
the	O
speed	O
of	O
developing	O
an	O
app	O
,	O
and	O
allow	O
its	O
user	O
to	O
focus	O
on	O
the	O
application	O
itself	O
.	O
</s>
<s>
With	O
PaaS	B-Application
,	O
the	O
customer	O
manages	O
applications	O
and	O
data	O
,	O
while	O
the	O
provider	O
(	O
in	O
public	O
PaaS	B-Application
)	O
or	O
IT	O
department	O
(	O
in	O
private	O
PaaS	B-Application
)	O
manages	O
runtime	B-Device
,	O
middleware	B-General_Concept
,	O
operating	B-General_Concept
system	I-General_Concept
,	O
virtualization	B-General_Concept
,	O
servers	B-Application
,	O
storage	B-General_Concept
and	O
networking	B-Architecture
.	O
</s>
<s>
PaaS	B-Application
offerings	O
may	O
also	O
include	O
facilities	O
for	O
application	O
design	O
,	O
application	O
development	O
,	O
testing	O
and	O
deployment	O
,	O
as	O
well	O
as	O
services	O
such	O
as	O
team	B-Application
collaboration	I-Application
,	O
web	O
service	O
integration	O
,	O
and	O
marshalling	B-Application
,	O
database	O
integration	O
,	O
security	O
,	O
scalability	O
,	O
storage	B-General_Concept
,	O
persistence	O
,	O
state	O
management	O
,	O
application	O
versioning	O
,	O
application	O
instrumentation	O
,	O
and	O
developer	O
community	O
facilitation	O
.	O
</s>
<s>
Besides	O
the	O
service	O
engineering	O
aspects	O
,	O
PaaS	B-Application
offerings	O
include	O
mechanisms	O
for	O
service	O
management	O
,	O
such	O
as	O
monitoring	O
,	O
workflow	O
management	O
,	O
discovery	O
and	O
reservation	O
.	O
</s>
<s>
The	O
advantages	O
of	O
PaaS	B-Application
are	O
primarily	O
that	O
it	O
allows	O
for	O
higher-level	O
programming	O
with	O
dramatically	O
reduced	O
complexity	O
;	O
the	O
overall	O
development	O
of	O
the	O
application	O
can	O
be	O
more	O
effective	O
,	O
as	O
it	O
has	O
built-in/self	O
up-and-down	O
ramping	O
infrastructure	O
resources	O
;	O
and	O
maintenance	O
and	O
enhancement	O
of	O
the	O
application	O
is	O
thus	O
easier	O
.	O
</s>
<s>
Disadvantages	O
of	O
various	O
PaaS	B-Application
providers	O
as	O
cited	O
by	O
their	O
users	O
include	O
increased	O
pricing	O
at	O
larger	O
scales	O
,	O
lack	O
of	O
operational	O
features	O
,	O
reduced	O
control	O
,	O
and	O
the	O
difficulties	O
of	O
traffic	O
routing	O
systems	O
.	O
</s>
<s>
There	O
are	O
several	O
types	O
of	O
PaaS	B-Application
,	O
including	O
public	O
,	O
private	O
and	O
hybrid	O
.	O
</s>
<s>
PaaS	B-Application
was	O
originally	O
intended	O
for	O
applications	O
on	O
public	O
cloud	O
services	O
,	O
before	O
expanding	O
to	O
include	O
private	O
and	O
hybrid	O
options	O
.	O
</s>
<s>
Public	O
PaaS	B-Application
is	O
derived	O
from	O
software	B-Architecture
as	I-Architecture
a	I-Architecture
service	I-Architecture
(	O
SaaS	B-Architecture
)	O
,	O
and	O
is	O
situated	O
in	O
cloud	O
computing	O
between	O
SaaS	B-Architecture
and	O
infrastructure	B-General_Concept
as	I-General_Concept
a	I-General_Concept
service	I-General_Concept
(	O
IaaS	B-General_Concept
)	O
.	O
</s>
<s>
SaaS	B-Architecture
is	O
software	O
hosted	O
in	O
the	O
cloud	O
so	O
that	O
it	O
does	O
not	O
take	O
up	O
hard	O
drive	O
space	O
on	O
the	O
computers	O
of	O
users	O
.	O
</s>
<s>
IaaS	B-General_Concept
provides	O
virtual	O
hardware	O
from	O
a	O
provider	O
with	O
adjustable	O
scalability	O
.	O
</s>
<s>
With	O
IaaS	B-General_Concept
,	O
the	O
user	O
still	O
has	O
to	O
manage	O
the	O
server	O
,	O
whereas	O
with	O
PaaS	B-Application
the	O
server	O
management	O
is	O
done	O
by	O
the	O
provider	O
.	O
</s>
<s>
A	O
private	O
PaaS	B-Application
can	O
typically	O
be	O
downloaded	O
and	O
installed	O
either	O
in	O
a	O
company	O
's	O
on-premises	O
data	B-Operating_System
center	I-Operating_System
,	O
or	O
in	O
a	O
public	O
cloud	O
.	O
</s>
<s>
Once	O
the	O
software	O
is	O
installed	O
on	O
one	O
or	O
more	O
machines	O
,	O
the	O
private	O
PaaS	B-Application
arranges	O
the	O
application	O
and	O
database	O
components	O
into	O
a	O
single	O
hosting	O
platform	O
.	O
</s>
<s>
Hybrid	O
PaaS	B-Application
is	O
typically	O
a	O
deployment	O
consisting	O
of	O
a	O
mix	O
of	O
public	O
and	O
private	O
deployments	O
.	O
</s>
<s>
A	O
communications	O
platform	B-Application
as	I-Application
a	I-Application
service	I-Application
(	O
CPaaS	O
)	O
is	O
a	O
cloud-based	O
platform	O
that	O
enables	O
developers	O
to	O
add	O
real-time	O
communications	O
features	O
(	O
voice	O
,	O
video	O
,	O
and	O
messaging	O
)	O
in	O
their	O
own	O
applications	O
without	O
building	O
back-end	O
infrastructure	O
and	O
interfaces	O
.	O
</s>
<s>
Hosted	O
PBX	O
,	O
cellular	O
networks	O
,	O
(	O
near	O
real-time	O
)	O
applications	O
typically	O
are	O
deployed	O
on	O
CPaaS	O
platforms	B-Device
.	O
</s>
<s>
Initiated	O
in	O
2012	O
,	O
mobile	O
PaaS	B-Application
(	O
mPaaS	O
)	O
provides	O
development	O
capabilities	O
for	O
mobile	O
app	O
designers	O
and	O
developers	O
.	O
</s>
<s>
Open	O
PaaS	B-Application
does	O
not	O
include	O
hosting	O
but	O
provides	O
open-source	O
software	O
allowing	O
a	O
PaaS	B-Application
provider	O
to	O
run	O
applications	O
in	O
an	O
open-source	O
environment	O
,	O
such	O
as	O
Google	B-Application
App	I-Application
Engine	I-Application
.	O
</s>
<s>
Some	O
open	O
platforms	B-Device
let	O
the	O
developer	O
use	O
any	O
programming	O
language	O
,	O
database	O
,	O
operating	B-General_Concept
system	I-General_Concept
or	O
server	O
to	O
deploy	O
their	O
applications	O
.	O
</s>
<s>
There	O
are	O
various	O
types	O
of	O
PaaS	B-Application
providers	O
.	O
</s>
<s>
Developers	O
can	O
write	O
an	O
application	O
and	O
upload	O
it	O
to	O
a	O
PaaS	B-Application
that	O
supports	O
their	O
software	O
language	O
of	O
choice	O
,	O
and	O
the	O
application	O
runs	O
on	O
that	O
PaaS	B-Application
.	O
</s>
