<s>
Node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
is	O
a	O
software	O
design	O
structured	O
around	O
the	O
notion	O
of	O
a	O
node	O
graph	O
.	O
</s>
<s>
Both	O
the	O
source	O
code	O
as	O
well	O
as	O
the	O
user	B-Application
interface	I-Application
is	O
designed	O
around	O
the	O
editing	O
and	O
composition	O
(	O
or	O
linking	O
)	O
of	O
atomic	O
functional	O
units	O
.	O
</s>
<s>
The	O
source	O
code	O
for	O
the	O
software	B-Application
application	I-Application
is	O
organized	O
into	O
atomic	O
functional	O
units	O
called	O
nodes	O
.	O
</s>
<s>
When	O
a	O
node	O
executes	B-General_Concept
its	O
functionality	O
,	O
it	O
retrieves	O
its	O
inputs	O
by	O
following	O
the	O
pointers	O
stored	O
in	O
its	O
inputs	O
to	O
retrieve	O
data	O
output	O
by	O
other	O
nodes	O
.	O
</s>
<s>
The	O
node	O
then	O
executes	B-General_Concept
its	O
operation	O
on	O
these	O
inputs	O
to	O
produce	O
its	O
own	O
outputs	O
.	O
</s>
<s>
The	O
user	B-Application
interface	I-Application
of	O
the	O
software	B-Application
application	I-Application
will	O
often	O
visually	O
display	O
the	O
node	O
graph	O
to	O
the	O
user	O
.	O
</s>
<s>
This	O
is	O
often	O
accomplished	O
by	O
using	O
the	O
GPU	B-Architecture
to	O
perform	O
the	O
rendering	O
which	O
is	O
subsequently	O
displayed	O
on	O
the	O
desktop	O
to	O
the	O
user	O
.	O
</s>
<s>
Common	O
APIs	B-General_Concept
for	O
the	O
GPU	B-Architecture
are	O
OpenGL	B-Application
and	O
DirectX	B-Application
.	O
</s>
<s>
The	O
use	O
of	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
started	O
in	O
the	O
1960s	O
.	O
</s>
<s>
The	O
fields	O
of	O
graphics	O
,	O
games	O
,	O
and	O
machine	O
learning	O
are	O
the	O
main	O
adopters	O
of	O
this	O
software	O
design	O
with	O
the	O
majority	O
of	O
tools	O
using	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
.	O
</s>
<s>
To	O
this	O
day	O
,	O
there	O
is	O
some	O
debate	O
as	O
to	O
the	O
benefits	O
of	O
visual	B-Language
programming	I-Language
and	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
.	O
</s>
<s>
Critics	O
highlight	O
how	O
visual	B-Language
programming	I-Language
is	O
too	O
restrictive	O
and	O
how	O
they	O
must	O
resort	O
to	O
modifying	O
source	O
code	O
or	O
scripts	O
to	O
accomplish	O
their	O
tasks	O
.	O
</s>
<s>
There	O
is	O
an	O
ongoing	O
effort	O
by	O
to	O
collect	O
snapshots	O
of	O
all	O
node	O
graph	O
user	B-Application
interfaces	I-Application
in	O
most	O
software	B-Application
applications	I-Application
.	O
</s>
<s>
The	O
effort	O
attempts	O
to	O
document	O
the	O
evolution	O
and	O
explosion	O
of	O
node	O
graph	O
user	B-Application
interfaces	I-Application
starting	O
from	O
their	O
initial	O
roots	O
.	O
</s>
<s>
Work	O
leading	O
to	O
node	B-Architecture
graph	I-Architecture
architectures	I-Architecture
and	O
visual	B-Language
programming	I-Language
seems	O
to	O
have	O
started	O
in	O
the	O
1960s	O
,	O
in	O
the	O
area	O
known	O
as	O
"	O
man-machine	O
communications	O
"	O
.	O
</s>
<s>
This	O
is	O
one	O
of	O
the	O
first	O
investigations	O
in	O
dataflow-based	B-Application
workflows	O
or	O
programs	O
.	O
</s>
<s>
His	O
work	O
is	O
often	O
thought	O
to	O
have	O
led	O
the	O
way	O
to	O
what	O
is	O
known	O
as	O
computer-aided	B-Application
design	I-Application
(	O
CAD	B-Application
)	O
today	O
.	O
</s>
<s>
A	O
program	O
's	O
execution	B-General_Concept
need	O
not	O
be	O
controlled	O
by	O
the	O
usual	O
explicit	O
sequential	O
flow	O
conventions	O
.	O
</s>
<s>
Their	O
work	O
was	O
related	O
to	O
the	O
RAND	B-Device
Tablet	I-Device
which	O
began	O
with	O
research	O
on	O
Sketchpad	B-Application
,	O
a	O
system	O
where	O
users	O
could	O
write	O
computer	O
commands	O
directly	O
on	O
a	O
tablet	O
,	O
conducted	O
by	O
Ivan	O
Sutherland	O
.	O
</s>
<s>
The	O
GRAIL	O
system	O
used	O
a	O
flowchart-based	O
graphical	B-Language
programming	I-Language
language	I-Language
and	O
could	O
recognize	O
handwritten	O
letters	O
and	O
gestures	O
.	O
</s>
<s>
Some	O
of	O
the	O
more	O
recent	O
uses	O
of	O
node	B-Architecture
graph	I-Architecture
architectures	I-Architecture
started	O
around	O
2005	O
.	O
</s>
<s>
In	O
the	O
paper	O
Hierarchical	O
Small	O
Worlds	O
in	O
Software	B-Architecture
Architecture	I-Architecture
author	O
Sergi	O
Valverde	O
argues	O
that	O
most	O
large	O
software	O
systems	O
are	O
built	O
in	O
a	O
modular	O
and	O
hierarchical	O
fashion	O
,	O
and	O
that	O
node	O
graphs	O
can	O
be	O
used	O
to	O
analyze	O
large	O
software	O
systems	O
.	O
</s>
<s>
Node	O
graphs	O
are	O
a	O
subset	O
of	O
the	O
broader	O
class	O
of	O
visual	B-Language
programming	I-Language
languages	I-Language
.	O
</s>
<s>
In	O
the	O
film	O
and	O
video	O
game	O
industries	O
node	O
graphs	O
are	O
synonymous	O
with	O
visual	B-Language
programming	I-Language
.	O
</s>
<s>
There	O
is	O
currently	O
some	O
debate	O
on	O
the	O
power	O
,	O
abstraction	O
,	O
and	O
need	O
of	O
node	O
graphs	O
and	O
visual	B-Language
programming	I-Language
languages	I-Language
.	O
</s>
<s>
Advocates	O
of	O
visual	B-Language
programming	I-Language
generally	O
emphasize	O
how	O
it	O
simplifies	O
programming	O
because	O
it	O
abstracts	O
away	O
many	O
details	O
and	O
only	O
exposes	O
controls	O
that	O
are	O
necessary	O
for	O
their	O
domain	O
.	O
</s>
<s>
Critics	O
of	O
visual	B-Language
programming	I-Language
generally	O
emphasize	O
how	O
it	O
does	O
not	O
offer	O
enough	O
control	O
,	O
and	O
how	O
for	O
more	O
complex	O
tasks	O
it	O
becomes	O
necessary	O
to	O
author	O
source	O
code	O
.	O
</s>
<s>
They	O
indicate	O
that	O
node	O
graphs	O
and	O
visual	B-Language
programming	I-Language
are	O
easy	O
to	O
understand	O
for	O
new	O
users	O
,	O
but	O
as	O
the	O
users	O
move	O
to	O
more	O
complex	O
tasks	O
they	O
often	O
need	O
to	O
resort	O
to	O
authoring	O
textual	O
source	O
code	O
.	O
</s>
<s>
Another	O
survey	O
focuses	O
on	O
peoples	O
beliefs	O
on	O
the	O
cognitive	O
effects	O
of	O
visual	B-Language
programming	I-Language
,	O
in	O
which	O
they	O
found	O
that	O
professional	O
programmers	O
are	O
the	O
most	O
skeptical	O
of	O
visual	B-Language
programming	I-Language
.	O
</s>
<s>
Other	O
studies	O
have	O
shown	O
in	O
psychological	O
experiments	O
that	O
visual	B-Language
programming	I-Language
can	O
have	O
significant	O
positive	O
effects	O
on	O
performance	O
in	O
cognitive	O
tasks	O
.	O
</s>
<s>
A	O
node	O
graph	O
in	O
the	O
context	O
of	O
software	B-Architecture
architecture	I-Architecture
refers	O
to	O
an	O
organization	O
of	O
software	O
functionality	O
into	O
atomic	O
units	O
known	O
as	O
nodes	O
,	O
and	O
where	O
nodes	O
can	O
be	O
connected	O
to	O
each	O
other	O
via	O
links	O
.	O
</s>
<s>
The	O
manipulation	O
of	O
nodes	O
and	O
links	O
in	O
the	O
node	O
graph	O
can	O
be	O
often	O
be	O
accomplished	O
through	O
a	O
programmable	O
API	B-General_Concept
or	O
through	O
a	O
visual	O
interface	O
by	O
using	O
the	O
mouse	B-Device
.	O
</s>
<s>
They	O
encapsulate	O
this	O
executable	B-General_Concept
functionality	O
and	O
will	O
often	O
take	O
inputs	O
and	O
produce	O
outputs	O
as	O
a	O
by-product	O
of	O
execution	B-General_Concept
.	O
</s>
<s>
Nodes	O
often	O
have	O
additional	O
parameters	O
,	O
that	O
define	O
their	O
execution	B-General_Concept
.	O
</s>
<s>
The	O
only	O
difference	O
is	O
that	O
these	O
values	O
are	O
controlled	O
directly	O
by	O
the	O
user	O
instead	O
of	O
being	O
output	O
by	O
another	O
node	O
as	O
a	O
by-product	O
of	O
its	O
execution	B-General_Concept
.	O
</s>
<s>
Inputs	O
and	O
outputs	O
are	O
crucial	O
to	O
storing	O
values	O
before	O
and	O
after	O
the	O
node	O
's	O
execution	B-General_Concept
.	O
</s>
<s>
The	O
type	O
of	O
a	O
node	O
indicates	O
which	O
compute	O
operation	O
it	O
will	O
perform	O
when	O
executed	B-General_Concept
.	O
</s>
<s>
Nuke	B-Language
,	O
a	O
popular	O
visual	O
effects	O
compositing	O
program	O
,	O
includes	O
hundreds	O
of	O
nodes	O
.	O
</s>
<s>
Group	O
nodes	O
in	O
Nuke	B-Language
.	O
</s>
<s>
Software	B-Application
applications	I-Application
using	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
will	O
typically	O
expose	O
the	O
node	O
graph	O
visually	O
or	O
graphically	O
to	O
the	O
user	O
,	O
allowing	O
the	O
user	O
to	O
make	O
changes	O
to	O
the	O
node	O
graph	O
.	O
</s>
<s>
Using	O
the	O
mouse	B-Device
,	O
users	O
will	O
typically	O
be	O
able	O
to	O
:	O
</s>
<s>
Often	O
these	O
new	O
interfaces	O
are	O
being	O
designed	O
by	O
user	B-Application
interface	I-Application
specialists	O
and	O
graphical	O
designers	O
.	O
</s>
<s>
The	O
following	O
are	O
some	O
user	B-Application
interfaces	I-Application
designed	O
by	O
artists	O
and	O
designers	O
.	O
</s>
<s>
When	O
cycles	O
are	O
present	O
in	O
the	O
node	O
graph	O
,	O
the	O
evaluation	O
never	O
ends	O
as	O
nodes	O
are	O
continually	O
executed	B-General_Concept
by	O
following	O
links	O
.	O
</s>
<s>
The	O
use	O
of	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
in	O
software	O
design	O
is	O
especially	O
popular	O
in	O
the	O
film	O
and	O
video	O
game	O
industries	O
.	O
</s>
<s>
The	O
diagram	O
above	O
shows	O
a	O
simplified	O
user	B-Application
interface	I-Application
for	O
an	O
artistic	O
tool	O
for	O
editing	O
and	O
creating	O
videos	O
.	O
</s>
<s>
The	O
following	O
are	O
some	O
examples	O
of	O
software	O
using	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
in	O
the	O
film	O
and	O
video	O
game	O
industries	O
.	O
</s>
<s>
The	O
use	O
of	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
in	O
software	O
design	O
has	O
recently	O
become	O
very	O
popular	O
in	O
machine	O
learning	O
applications	O
.	O
</s>
<s>
The	O
following	O
are	O
examples	O
of	O
machine	O
learning	O
software	O
using	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
without	O
a	O
graphical	O
interface	O
for	O
the	O
node	O
graphs	O
.	O
</s>
<s>
The	O
following	O
are	O
some	O
examples	O
of	O
machine	O
learning	O
software	O
using	O
node	B-Architecture
graph	I-Architecture
architecture	I-Architecture
.	O
</s>
