<s>
An	O
elastic	O
cloud	O
is	O
a	O
cloud	B-Architecture
computing	I-Architecture
offering	O
that	O
provides	O
variable	O
service	O
levels	O
based	O
on	O
changing	O
needs	O
.	O
</s>
<s>
Elasticity	B-General_Concept
is	O
an	O
attribute	O
that	O
can	O
be	O
applied	O
to	O
most	O
cloud	B-Architecture
services	I-Architecture
.	O
</s>
<s>
It	O
states	O
that	O
the	O
capacity	O
and	O
performance	O
of	O
any	O
given	O
cloud	B-Architecture
service	I-Architecture
can	O
expand	O
or	O
contract	O
according	O
to	O
a	O
customer	O
's	O
requirements	O
and	O
that	O
this	O
can	O
potentially	O
be	O
changed	O
automatically	O
as	O
a	O
consequence	O
of	O
some	O
software-driven	O
event	O
or	O
,	O
at	O
worst	O
,	O
can	O
be	O
reconfigured	O
quickly	O
by	O
the	O
customer	O
's	O
infrastructure	O
management	O
team	O
.	O
</s>
<s>
Elasticity	B-General_Concept
has	O
been	O
described	O
as	O
one	O
of	O
the	O
five	O
main	O
principles	O
of	O
cloud	B-Architecture
computing	I-Architecture
by	O
Rosenburg	O
and	O
Mateos	O
in	B-Architecture
The	I-Architecture
Cloud	I-Architecture
at	O
Your	O
Service	O
-	O
Manning	O
2011	O
.	O
</s>
<s>
however	O
,	O
the	O
first	O
practical	O
implementation	O
was	O
a	O
consequence	O
of	O
a	O
strategy	O
toleverage	O
Amazon	B-Application
's	O
excess	O
data	O
center	O
capacity	O
.	O
</s>
<s>
only	O
offering	O
this	O
service	O
as	O
an	O
element	O
of	O
their	O
public	O
cloud	B-Architecture
service	I-Architecture
.	O
</s>
<s>
public	O
sectors	O
,	O
have	O
been	O
slow	O
adopters	O
of	O
cloud	B-Architecture
technologies	I-Architecture
.	O
</s>
<s>
still	O
retains	O
elements	O
of	O
elasticity	B-General_Concept
and	O
the	O
potential	O
to	O
bill	O
by	O
consumption	O
.	O
</s>
