<s>
and	O
software	B-General_Concept
engineering	I-General_Concept
,	O
provides	O
a	O
record	O
of	O
all	O
interface	O
information	O
(	O
such	O
as	O
drawings	O
,	O
diagrams	O
,	O
tables	O
,	O
and	O
textual	O
information	O
)	O
generated	O
for	O
a	O
project	O
.	O
</s>
<s>
The	O
inputs	O
and	O
outputs	O
of	O
a	O
single	O
system	O
,	O
documented	O
in	O
individual	O
SIRS	O
(	O
Software	O
Interface	O
Requirements	O
Specifications	O
)	O
and	O
HIRS	O
(	O
Hardware	O
Interface	O
Requirements	O
Specifications	O
)	O
documents	O
,	O
would	O
fall	O
under	O
"	O
The	O
Wikipedia	O
Interface	B-Application
Control	I-Application
Document	I-Application
"	O
.	O
</s>
<s>
The	O
complete	O
interface	O
protocol	O
from	O
the	O
lowest	O
physical	O
elements	O
(	O
e.g.	O
,	O
the	O
mating	O
plugs	O
,	O
the	O
electrical	O
signal	O
voltage	O
levels	O
)	O
to	O
the	O
highest	O
logical	O
levels	O
(	O
e.g.	O
,	O
the	O
level	O
7	O
application	B-Application
layer	I-Application
of	O
the	O
OSI	O
model	O
)	O
would	O
each	O
be	O
documented	O
in	O
the	O
appropriate	O
interface	O
requirements	O
spec	O
and	O
fall	O
under	O
a	O
single	O
ICD	O
for	O
the	O
"	O
system	O
"	O
.	O
</s>
<s>
Interface	B-Application
control	I-Application
documents	I-Application
are	O
a	O
key	O
element	O
of	O
systems	O
engineering	O
as	O
they	O
control	O
the	O
documented	O
interface(s )	O
of	O
a	O
system	O
,	O
as	O
well	O
as	O
specify	O
a	O
set	O
of	O
interface	O
versions	O
that	O
work	O
together	O
,	O
and	O
thereby	O
bound	O
the	O
requirements	O
.	O
</s>
<s>
An	O
application	B-Application
programming	I-Application
interface	I-Application
is	O
a	O
form	O
of	O
interface	O
for	O
a	O
software	O
system	O
,	O
in	O
that	O
it	O
describes	O
how	O
to	O
access	O
the	O
functions	O
and	O
services	O
provided	O
by	O
a	O
system	O
via	O
an	O
interface	O
.	O
</s>
