<s>
An	O
open	B-Application
API	I-Application
(	O
often	O
referred	O
to	O
as	O
a	O
public	O
API	B-General_Concept
)	O
is	O
a	O
publicly	O
available	O
application	B-Application
programming	I-Application
interface	I-Application
that	O
provides	O
developers	O
with	O
programmatic	O
access	O
to	O
a	O
(	O
possibly	O
proprietary	O
)	O
software	B-Application
application	I-Application
or	O
web	O
service	O
.	O
</s>
<s>
Open	B-Application
APIs	I-Application
are	O
APIs	B-General_Concept
that	O
are	O
published	O
on	O
the	O
internet	O
and	O
are	O
free	O
to	O
access	O
by	O
consumers	O
.	O
</s>
<s>
There	O
is	O
no	O
universally	O
accepted	O
definition	O
of	O
the	O
term	O
"	O
Open	B-Application
API	I-Application
"	O
and	O
it	O
may	O
be	O
used	O
to	O
mean	O
a	O
variety	O
of	O
things	O
in	O
different	O
contexts	O
,	O
including	O
:	O
</s>
<s>
An	O
API	B-General_Concept
for	O
use	O
by	O
developers	O
and	O
other	O
users	O
with	O
relatively	O
few	O
restrictions	O
.	O
</s>
<s>
An	O
API	B-General_Concept
backed	O
by	O
open	O
data	O
.	O
</s>
<s>
An	O
API	B-General_Concept
based	O
on	O
an	O
open	O
standard	O
,	O
which	O
specifies	O
the	O
mechanism	O
by	O
which	O
a	O
consumer	O
queries	O
the	O
API	B-General_Concept
and	O
interprets	O
its	O
responses	O
.	O
</s>
<s>
A	O
private	O
API	B-General_Concept
is	O
an	O
interface	O
that	O
opens	O
parts	O
of	O
an	O
organization	O
's	O
backend	O
data	O
and	O
application	O
functionality	O
for	O
use	O
by	O
developers	O
working	O
within	O
(	O
or	O
contractors	O
working	O
for	O
)	O
that	O
organization	O
.	O
</s>
<s>
Private	O
APIs	B-General_Concept
are	O
only	O
exposed	O
to	O
internal	O
developers	O
therefore	O
the	O
API	B-General_Concept
publishers	O
have	O
total	O
control	O
over	O
what	O
and	O
how	O
applications	O
are	O
developed	O
.	O
</s>
<s>
Private	O
APIs	B-General_Concept
offer	O
substantial	O
benefits	O
with	O
regards	O
to	O
internal	O
collaboration	O
.	O
</s>
<s>
Using	O
a	O
private	O
API	B-General_Concept
across	O
an	O
organization	O
allows	O
for	O
greater	O
shared	O
awareness	O
of	O
the	O
internal	O
data	O
models	O
.	O
</s>
<s>
Private	O
APIs	B-General_Concept
can	O
significantly	O
diminish	O
the	O
development	O
time	O
needed	O
to	O
manipulate	O
and	O
build	O
internal	O
systems	O
that	O
maximise	O
productivity	O
and	O
create	O
customer-facing	O
applications	O
that	O
improve	O
market	O
reach	O
and	O
add	O
value	O
to	O
existing	O
offerings	O
.	O
</s>
<s>
Private	O
APIs	B-General_Concept
can	O
be	O
made	O
"	O
private	O
"	O
in	O
a	O
number	O
of	O
ways	O
.	O
</s>
<s>
Some	O
Web-based	O
APIs	B-General_Concept
may	O
be	O
authenticated	O
by	O
keys	O
,	O
both	O
discoverable	O
by	O
analysis	O
of	O
application	O
traffic	O
.	O
</s>
<s>
macOS	O
furthermore	O
uses	O
an	O
"	O
entitlement	O
"	O
,	O
granted	O
only	O
by	O
digital	O
signature	O
,	O
to	O
control	O
access	O
to	O
private	O
APIs	B-General_Concept
in	O
the	O
system	O
.	O
</s>
<s>
Private	O
APIs	B-General_Concept
are	O
by	O
definition	O
without	O
any	O
guarantee	O
to	O
the	O
third-party	O
developer	O
choosing	O
to	O
uncover	O
and	O
use	O
them	O
.	O
</s>
<s>
In	O
contrast	O
to	O
a	O
private	O
API	B-General_Concept
,	O
an	O
open	B-Application
API	I-Application
is	O
publicly	O
available	O
for	O
all	O
developers	O
to	O
access	O
.	O
</s>
<s>
Open	B-Application
APIs	I-Application
can	O
significantly	O
increase	O
revenue	O
without	O
the	O
business	O
having	O
to	O
invest	O
in	O
hiring	O
new	O
developers	O
making	O
them	O
a	O
very	O
profitable	O
software	B-Application
application	I-Application
.	O
</s>
<s>
For	O
example	O
,	O
publishing	O
open	B-Application
APIs	I-Application
can	O
make	O
it	O
harder	O
for	O
organisations	O
to	O
control	O
the	O
experience	O
end	O
users	O
have	O
with	O
their	O
information	O
assets	O
.	O
</s>
<s>
Open	B-Application
API	I-Application
publishers	O
cannot	O
assume	O
client	O
apps	O
built	O
on	O
their	O
APIs	B-General_Concept
will	O
offer	O
a	O
good	O
user	O
experience	O
.	O
</s>
<s>
Open	B-Application
APIs	I-Application
can	O
be	O
used	O
by	O
businesses	O
seeking	O
to	O
leverage	O
the	O
ever-growing	O
community	O
of	O
freelancing	O
developers	O
who	O
have	O
the	O
ability	O
to	O
create	O
innovative	O
applications	O
that	O
add	O
value	O
to	O
their	O
core	O
business	O
.	O
</s>
<s>
Open	B-Application
APIs	I-Application
are	O
favoured	O
in	O
the	O
business	O
sphere	O
as	O
they	O
simultaneously	O
increase	O
the	O
production	O
of	O
new	O
ideas	O
without	O
investing	O
directly	O
in	O
development	O
efforts	O
.	O
</s>
<s>
Businesses	O
often	O
tailor	O
their	O
APIs	B-General_Concept
to	O
target	O
specific	O
developer	O
audiences	O
that	O
they	O
feel	O
will	O
be	O
most	O
effective	O
in	O
creating	O
valuable	O
new	O
applications	O
.	O
</s>
<s>
However	O
,	O
an	O
API	B-General_Concept
can	O
significantly	O
diminish	O
an	O
application	O
's	O
functionality	O
if	O
it	O
is	O
overloaded	O
with	O
features	O
.	O
</s>
<s>
For	O
example	O
,	O
Yahoo	B-Application
's	O
open	O
search	O
API	B-General_Concept
allows	O
developers	O
to	O
integrate	O
Yahoo	B-Application
search	I-Application
into	O
their	O
own	O
software	B-Application
applications	I-Application
.	O
</s>
<s>
The	O
addition	O
of	O
this	O
API	B-General_Concept
provides	O
search	O
functionality	O
to	O
the	O
developer	O
's	O
application	O
whilst	O
also	O
increasing	O
search	O
traffic	O
for	O
Yahoo	B-Application
's	O
search	O
engine	O
hence	O
benefitting	O
both	O
parties	O
.	O
</s>
<s>
With	O
respect	O
to	O
Facebook	B-Application
and	O
Twitter	B-Application
,	O
we	O
can	O
see	O
how	O
third	O
parties	O
have	O
enriched	O
these	O
services	O
with	O
their	O
own	O
code	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
ability	O
to	O
create	O
an	O
account	O
on	O
an	O
external	O
site/app	O
using	O
your	O
Facebook	B-Application
credentials	O
is	O
made	O
possible	O
using	O
Facebook	B-Application
's	O
open	B-Application
API	I-Application
.	O
</s>
<s>
Many	O
large	O
technology	O
firms	O
,	O
such	O
as	O
Twitter	B-Application
,	O
LinkedIn	B-Application
and	O
Facebook	B-Application
,	O
allow	O
the	O
use	O
of	O
their	O
service	O
by	O
third	O
parties	O
and	O
competitors	O
.	O
</s>
<s>
With	O
the	O
rise	O
in	O
prominence	O
of	O
HTML5	B-Application
and	O
Web	O
2.0	O
,	O
the	O
modern	O
browsing	O
experience	O
has	O
become	O
interactive	O
and	O
dynamic	O
and	O
this	O
has	O
,	O
in	O
part	O
,	O
been	O
accelerated	O
through	O
the	O
use	O
of	O
open	B-Application
APIs	I-Application
.	O
</s>
<s>
Some	O
open	B-Application
APIs	I-Application
fetch	O
data	O
from	O
the	O
database	O
behind	O
a	O
website	O
and	O
these	O
are	O
called	O
Web	B-General_Concept
APIs	I-General_Concept
.	O
</s>
<s>
For	O
example	O
,	O
Google	O
's	O
YouTube	O
API	B-General_Concept
allows	O
developers	O
to	O
integrate	O
YouTube	O
into	O
their	O
applications	O
by	O
providing	O
the	O
capability	O
to	O
search	O
for	O
videos	O
,	O
retrieve	O
standard	O
feeds	O
,	O
and	O
see	O
related	O
content	O
.	O
</s>
<s>
Web	B-General_Concept
APIs	I-General_Concept
are	O
used	O
for	O
exchanging	O
information	O
with	O
a	O
website	O
either	O
by	O
receiving	O
or	O
by	O
sending	O
data	O
.	O
</s>
<s>
When	O
a	O
web	B-General_Concept
API	I-General_Concept
fetches	O
data	O
from	O
a	O
website	O
,	O
the	O
application	O
makes	O
a	O
carefully	O
constructed	O
HTTP	O
request	O
to	O
the	O
server	O
the	O
site	O
is	O
stored	O
on	O
.	O
</s>
