<s>
In	O
computer	B-General_Concept
programming	I-General_Concept
,	O
dataflow	B-Application
programming	I-Application
is	O
a	O
programming	O
paradigm	O
that	O
models	O
a	O
program	O
as	O
a	O
directed	O
graph	O
of	O
the	O
data	O
flowing	O
between	O
operations	O
,	O
thus	O
implementing	O
dataflow	B-Application
principles	O
and	O
architecture	O
.	O
</s>
<s>
Dataflow	B-Application
programming	I-Application
languages	I-Application
share	O
some	O
features	O
of	O
functional	B-Language
languages	I-Language
,	O
and	O
were	O
generally	O
developed	O
in	O
order	O
to	O
bring	O
some	O
functional	B-Language
concepts	O
to	O
a	O
language	O
more	O
suitable	O
for	O
numeric	O
processing	O
.	O
</s>
<s>
Some	O
authors	O
use	O
the	O
term	O
datastream	O
instead	O
of	O
dataflow	B-Application
to	O
avoid	O
confusion	O
with	O
dataflow	B-Application
computing	O
or	O
dataflow	B-General_Concept
architecture	I-General_Concept
,	O
based	O
on	O
an	O
indeterministic	O
machine	O
paradigm	O
.	O
</s>
<s>
Dataflow	B-Application
programming	I-Application
was	O
pioneered	O
by	O
Jack	O
Dennis	O
and	O
his	O
graduate	O
students	O
at	O
MIT	O
in	O
the	O
1960s	O
.	O
</s>
<s>
control	O
flow	O
(	O
indicating	O
that	O
the	O
program	O
chooses	O
a	O
specific	O
path	O
)	O
,	O
or	O
imperative	B-Application
programming	I-Application
.	O
</s>
<s>
In	O
contrast	O
,	O
dataflow	B-Application
programming	I-Application
emphasizes	O
the	O
movement	O
of	O
data	O
and	O
models	O
programs	O
as	O
a	O
series	O
of	O
connections	O
.	O
</s>
<s>
Explicitly	O
defined	O
inputs	O
and	O
outputs	O
connect	O
operations	O
,	O
which	O
function	O
like	O
black	B-Device
boxes	I-Device
.	O
</s>
<s>
Thus	O
,	O
dataflow	B-Application
languages	I-Application
are	O
inherently	O
parallel	O
and	O
can	O
work	O
well	O
in	O
large	O
,	O
decentralized	O
systems	O
.	O
</s>
<s>
One	O
of	O
the	O
key	O
concepts	O
in	O
computer	B-General_Concept
programming	I-General_Concept
is	O
the	O
idea	O
of	O
state	B-Application
,	O
essentially	O
a	O
snapshot	O
of	O
various	O
conditions	O
in	O
the	O
system	O
.	O
</s>
<s>
Most	O
programming	O
languages	O
require	O
a	O
considerable	O
amount	O
of	O
state	B-Application
information	O
,	O
which	O
is	O
generally	O
hidden	O
from	O
the	O
programmer	O
.	O
</s>
<s>
Often	O
,	O
the	O
computer	O
itself	O
has	O
no	O
idea	O
which	O
piece	O
of	O
information	O
encodes	O
the	O
enduring	O
state	B-Application
.	O
</s>
<s>
This	O
is	O
a	O
serious	O
problem	O
,	O
as	O
the	O
state	B-Application
information	O
needs	O
to	O
be	O
shared	O
across	O
multiple	O
processors	O
in	O
parallel	B-Operating_System
processing	I-Operating_System
machines	O
.	O
</s>
<s>
Most	O
languages	O
force	O
the	O
programmer	O
to	O
add	O
extra	O
code	O
to	O
indicate	O
which	O
data	O
and	O
parts	O
of	O
the	O
code	O
are	O
important	O
to	O
the	O
state	B-Application
.	O
</s>
<s>
Explicit	O
parallelism	B-Operating_System
is	O
one	O
of	O
the	O
main	O
reasons	O
for	O
the	O
poor	O
performance	O
of	O
Enterprise	B-Language
Java	I-Language
Beans	I-Language
when	O
building	O
data-intensive	O
,	O
non-OLTP	O
applications	O
.	O
</s>
<s>
Where	O
a	O
sequential	O
program	O
can	O
be	O
imagined	O
as	O
a	O
single	O
worker	O
moving	O
between	O
tasks	O
(	O
operations	O
)	O
,	O
a	O
dataflow	B-Application
program	O
is	O
more	O
like	O
a	O
series	O
of	O
workers	O
on	O
an	O
assembly	O
line	O
,	O
each	O
doing	O
a	O
specific	O
task	O
whenever	O
materials	O
are	O
available	O
.	O
</s>
<s>
Since	O
the	O
operations	O
are	O
only	O
concerned	O
with	O
the	O
availability	O
of	O
data	O
inputs	O
,	O
they	O
have	O
no	O
hidden	O
state	B-Application
to	O
track	O
,	O
and	O
are	O
all	O
"	O
ready	O
"	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
Dataflow	B-Application
programs	O
are	O
represented	O
in	O
different	O
ways	O
.	O
</s>
<s>
A	O
traditional	O
program	O
is	O
usually	O
represented	O
as	O
a	O
series	O
of	O
text	O
instructions	O
,	O
which	O
is	O
reasonable	O
for	O
describing	O
a	O
serial	O
system	O
which	O
pipes	B-Operating_System
data	O
between	O
small	O
,	O
single-purpose	O
tools	O
that	O
receive	O
,	O
process	O
,	O
and	O
return	O
.	O
</s>
<s>
Dataflow	B-Application
programs	O
start	O
with	O
an	O
input	O
,	O
perhaps	O
the	O
command	B-Application
line	I-Application
parameters	O
,	O
and	O
illustrate	O
how	O
that	O
data	O
is	O
used	O
and	O
modified	O
.	O
</s>
<s>
The	O
flow	B-Application
of	I-Application
data	I-Application
is	O
explicit	O
,	O
often	O
visually	O
illustrated	O
as	O
a	O
line	O
or	O
pipe	O
.	O
</s>
<s>
In	O
terms	O
of	O
encoding	O
,	O
a	O
dataflow	B-Application
program	O
might	O
be	O
implemented	O
as	O
a	O
hash	B-Algorithm
table	I-Algorithm
,	O
with	O
uniquely	O
identified	O
inputs	O
as	O
the	O
keys	O
,	O
used	O
to	O
look	O
up	O
pointers	O
to	O
the	O
instructions	O
.	O
</s>
<s>
For	O
parallel	O
operation	O
,	O
only	O
the	O
list	O
needs	O
to	O
be	O
shared	O
;	O
it	O
is	O
the	O
state	B-Application
of	O
the	O
entire	O
program	O
.	O
</s>
<s>
Thus	O
the	O
task	O
of	O
maintaining	O
state	B-Application
is	O
removed	O
from	O
the	O
programmer	O
and	O
given	O
to	O
the	O
language	O
's	O
runtime	B-Device
.	O
</s>
<s>
On	O
machines	O
with	O
a	O
single	O
processor	O
core	O
where	O
an	O
implementation	O
designed	O
for	O
parallel	O
operation	O
would	O
simply	O
introduce	O
overhead	O
,	O
this	O
overhead	O
can	O
be	O
removed	O
completely	O
by	O
using	O
a	O
different	O
runtime	B-Device
.	O
</s>
<s>
Some	O
recent	O
dataflow	B-Application
libraries	O
such	O
as	O
Differential/Timely	O
Dataflow	B-Application
have	O
used	O
incremental	O
computing	O
for	O
much	O
more	O
efficient	O
data	O
processing	O
.	O
</s>
<s>
A	O
pioneer	O
dataflow	B-Application
language	I-Application
was	O
BLODI	O
(	O
BLOck	O
DIagram	O
)	O
,	O
developed	O
by	O
John	O
Larry	O
Kelly	O
,	O
Jr.	O
,	O
Carol	O
Lochbaum	O
and	O
Victor	O
A	O
.	O
Vyssotsky	O
for	O
specifying	O
sampled	O
data	O
systems	O
.	O
</s>
<s>
A	O
BLODI	O
specification	O
of	O
functional	B-Language
units	O
(	O
amplifiers	O
,	O
adders	O
,	O
delay	O
lines	O
,	O
etc	O
.	O
)	O
</s>
<s>
and	O
their	O
interconnections	O
was	O
compiled	B-Language
into	O
a	O
single	O
loop	O
that	O
updated	O
the	O
entire	O
system	O
for	O
one	O
clock	O
tick	O
.	O
</s>
<s>
In	O
a	O
1966	O
Ph.D.	O
thesis	O
,	O
The	O
On-line	O
Graphical	O
Specification	O
of	O
Computer	O
Procedures	O
,	O
Bert	O
Sutherland	O
created	O
one	O
of	O
the	O
first	O
graphical	O
dataflow	B-Application
programming	I-Application
frameworks	O
in	O
order	O
to	O
make	O
parallel	B-Operating_System
programming	I-Operating_System
easier	O
.	O
</s>
<s>
Subsequent	O
dataflow	B-Application
languages	I-Application
were	O
often	O
developed	O
at	O
the	O
large	O
supercomputer	B-Architecture
labs	O
.	O
</s>
<s>
POGOL	O
,	O
an	O
otherwise	O
conventional	O
data-processing	O
language	O
developed	O
at	O
NSA	O
,	O
compiled	B-Language
large-scale	O
applications	O
composed	O
of	O
multiple	O
file-to-file	O
operations	O
,	O
e.g.	O
</s>
<s>
SISAL	B-Language
,	O
a	O
popular	O
dataflow	B-Application
language	I-Application
developed	O
at	O
Lawrence	O
Livermore	O
National	O
Laboratory	O
,	O
looks	O
like	O
most	O
statement-driven	O
languages	O
,	O
but	O
variables	O
should	O
be	O
assigned	O
once	O
.	O
</s>
<s>
This	O
allows	O
the	O
compiler	B-Language
to	O
easily	O
identify	O
the	O
inputs	O
and	O
outputs	O
.	O
</s>
<s>
A	O
number	O
of	O
offshoots	O
of	O
SISAL	B-Language
have	O
been	O
developed	O
,	O
including	O
SAC	B-Language
,	O
Single	O
Assignment	O
C	B-Language
,	O
which	O
tries	O
to	O
remain	O
as	O
close	O
to	O
the	O
popular	O
C	B-Language
programming	I-Language
language	I-Language
as	O
possible	O
.	O
</s>
<s>
The	O
United	O
States	O
Navy	O
funded	O
development	O
of	O
ACOS	O
and	O
SPGN	O
(	O
signal	B-Application
processing	O
graph	O
notation	O
)	O
starting	O
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
A	O
more	O
radical	O
concept	O
is	O
Prograph	B-Language
,	O
in	O
which	O
programs	O
are	O
constructed	O
as	O
graphs	O
onscreen	O
,	O
and	O
variables	O
are	O
replaced	O
entirely	O
with	O
lines	O
linking	O
inputs	O
to	O
outputs	O
.	O
</s>
<s>
Incidentally	O
,	O
Prograph	B-Language
was	O
originally	O
written	O
on	O
the	O
Macintosh	B-Device
,	O
which	O
remained	O
single-processor	O
until	O
the	O
introduction	O
of	O
the	O
DayStar	O
Genesis	O
MP	O
in	O
1996	O
.	O
</s>
<s>
There	O
are	O
many	O
hardware	O
architectures	O
oriented	O
toward	O
the	O
efficient	O
implementation	O
of	O
dataflow	B-Application
programming	I-Application
models	O
.	O
</s>
<s>
MIT	O
's	O
tagged	O
token	O
dataflow	B-General_Concept
architecture	I-General_Concept
was	O
designed	O
by	O
Greg	O
Papadopoulos	O
.	O
</s>
<s>
Data	B-Application
flow	I-Application
has	O
been	O
proposed	O
as	O
an	O
abstraction	O
for	O
specifying	O
the	O
global	O
behavior	O
of	O
distributed	O
system	O
components	O
:	O
in	O
the	O
live	B-Operating_System
distributed	I-Operating_System
objects	I-Operating_System
programming	O
model	O
,	O
distributed	B-Operating_System
data	I-Operating_System
flows	I-Operating_System
are	O
used	O
to	O
store	O
and	O
communicate	O
state	B-Application
,	O
and	O
as	O
such	O
,	O
they	O
play	O
the	O
role	O
analogous	O
to	O
variables	O
,	O
fields	O
,	O
and	O
parameters	O
in	O
Java-like	O
programming	O
languages	O
.	O
</s>
<s>
Dataflow	B-Application
programming	I-Application
languages	I-Application
include	O
:	O
</s>
<s>
Cuneiform	B-Language
,	O
a	O
functional	B-Language
workflow	O
language	O
.	O
</s>
<s>
Orange	B-Application
-	O
An	O
open-source	O
,	O
visual	O
programming	O
tool	O
for	O
data	B-Application
mining	I-Application
,	O
statistical	O
data	B-General_Concept
analysis	I-General_Concept
,	O
and	O
machine	O
learning	O
.	O
</s>
<s>
Apache	B-Language
Beam	I-Language
:	O
Java/Scala	O
SDK	O
that	O
unifies	O
streaming	O
(	O
and	O
batch	O
)	O
processing	O
with	O
several	O
execution	O
engines	O
supported	O
(	O
Apache	B-Language
Spark	I-Language
,	O
Apache	B-Application
Flink	I-Application
,	O
Google	O
Dataflow	B-Application
etc	O
.	O
)	O
</s>
<s>
SystemC	B-Language
:	O
Library	O
for	O
C++	O
,	O
mainly	O
aimed	O
at	O
hardware	O
design	O
.	O
</s>
<s>
TensorFlow	B-Language
:	O
A	O
machine-learning	O
library	O
based	O
on	O
dataflow	B-Application
programming	I-Application
.	O
</s>
