<s>
ToonTalk	B-Language
is	O
a	O
computer	O
programming	O
system	O
intended	O
to	O
be	O
programmed	O
by	O
children	O
.	O
</s>
<s>
It	O
is	O
one	O
of	O
the	O
few	O
successful	O
implementations	O
outside	O
academia	O
of	O
the	O
concurrent	B-Application
constraint	I-Application
logic	I-Application
programming	I-Application
paradigm	O
.	O
</s>
<s>
It	O
was	O
created	O
by	O
Kenneth	O
M	O
.	O
Kahn	O
in	O
1995	O
,	O
and	O
implemented	O
as	O
part	O
of	O
the	O
ToonTalk	B-Language
IDE	O
,	O
a	O
software	O
package	O
distributed	O
worldwide	O
between	O
1996	O
and	O
2009	O
.	O
</s>
<s>
Beginning	O
2014	O
a	O
JavaScript	O
HTML5	O
version	O
of	O
ToonTalk	B-Language
called	O
ToonTalk	B-Language
Reborn	O
for	O
the	O
Web	O
has	O
been	O
available	O
.	O
</s>
<s>
It	O
runs	O
on	O
any	O
modern	O
web	O
browser	O
and	O
differs	O
from	O
the	O
desktop	O
version	O
of	O
ToonTalk	B-Language
in	O
a	O
few	O
ways	O
.	O
</s>
<s>
ToonTalk	B-Language
programs	O
can	O
run	O
on	O
any	O
DOM	O
element	O
and	O
various	O
browser	O
capabilities	O
(	O
audio	O
,	O
video	O
,	O
style	O
sheets	O
,	O
speech	O
input	O
and	O
output	O
,	O
and	O
browser	O
events	O
)	O
are	O
available	O
to	O
ToonTalk	B-Language
programs	O
.	O
</s>
<s>
ToonTalk	B-Language
Reborn	O
is	O
free	O
and	O
open	O
source	O
.	O
</s>
<s>
Beyond	O
its	O
life	O
as	O
a	O
commercial	O
product	O
,	O
ToonTalk	B-Language
evolved	O
via	O
significant	O
academic	O
use	O
in	O
various	O
research	O
projects	O
,	O
notably	O
at	O
the	O
London	O
Knowledge	O
Lab	O
and	O
the	O
Institute	O
of	O
Education	O
-	O
projects	O
Playground	O
and	O
WebLabs	O
,	O
which	O
involved	O
research	O
partners	O
from	O
Cambridge	O
(	O
Addison	O
Wesley	O
Longman	O
through	O
their	O
Logotron	O
subsidiary	O
)	O
,	O
Portugal	O
(	O
Cnotinfor	O
and	O
the	O
University	O
of	O
Lisbon	O
)	O
,	O
Sweden	O
(	O
Royal	O
Institute	O
of	O
Technology	O
)	O
,	O
Slovakia	O
(	O
Comenius	O
University	O
)	O
,	O
Bulgaria	O
(	O
Sofia	O
University	O
)	O
,	O
Cyprus	O
(	O
University	O
of	O
Cyprus	O
)	O
,	O
and	O
Italy	O
(	O
Institute	O
for	O
Educational	O
Technology	O
of	O
the	O
Consiglio	O
Nazionale	O
delle	O
Ricerche	O
)	O
.	O
</s>
<s>
It	O
was	O
also	O
source	O
of	O
academic	O
interest	O
in	O
Sweden	O
,	O
where	O
Mikael	O
Kindborg	O
proposed	O
a	O
static	O
representation	O
of	O
ToonTalk	B-Language
programs	O
and	O
in	O
Portugal	O
,	O
where	O
Leonel	O
Morgado	O
studied	O
its	O
potential	O
to	O
enable	O
computer	O
programming	O
by	O
preliterate	O
children	O
.	O
</s>
<s>
ToonTalk	B-Language
was	O
influenced	O
by	O
the	O
Janus	B-Language
computer	I-Language
programming	I-Language
language	I-Language
and	O
the	O
Actor	B-Application
model	I-Application
.	O
</s>
<s>
The	O
main	O
communication	O
abstraction	O
in	O
ToonTalk	B-Language
is	O
the	O
bird/nest	O
pair	O
.	O
</s>
<s>
A	O
ToonTalk	B-Language
program	O
is	O
a	O
sequence	O
of	O
rules	O
,	O
where	O
each	O
rule	O
has	O
a	O
head	O
and	O
a	O
tail	O
.	O
</s>
<s>
In	O
ToonTalk	B-Language
's	O
presentation	O
,	O
a	O
rule	O
appears	O
as	O
a	O
robot	O
,	O
a	O
program	O
as	O
a	O
team	O
of	O
robots	O
,	O
and	O
a	O
tuple	O
as	O
a	O
box	O
that	O
can	O
have	O
any	O
number	O
of	O
holes	O
or	O
compartments	O
in	O
which	O
things	O
may	O
be	O
placed	O
.	O
</s>
<s>
Consequently	O
,	O
a	O
nest	O
can	O
be	O
used	O
to	O
program	O
a	O
future	B-Operating_System
.	O
</s>
<s>
ToonTalk	B-Language
can	O
be	O
given	O
an	O
imperative	O
reading	O
or	O
a	O
declarative	O
reading	O
.	O
</s>
<s>
If	O
we	O
ignore	O
certain	O
constructs	O
designed	O
to	O
facilitate	O
I/O	O
,	O
we	O
can	O
see	O
ToonTalk	B-Language
as	O
not	O
having	O
any	O
shared	O
access	O
to	O
mutable	O
memory	O
.	O
</s>
<s>
The	O
bird/nest	O
mechanism	O
resembles	O
the	O
communication	O
in	O
the	O
Actor	B-Application
model	I-Application
,	O
but	O
with	O
the	O
additional	O
power	O
to	O
be	O
able	O
to	O
pass	O
nests	O
around	O
and	O
for	O
a	O
process	O
to	O
hold	O
more	O
than	O
one	O
nest	O
(	O
which	O
is	O
also	O
true	O
in	O
Janus	B-Language
)	O
.	O
</s>
<s>
A	O
difference	O
between	O
communication	O
in	O
the	O
Actor	B-Application
model	I-Application
and	O
in	O
ToonTalk	B-Language
is	O
that	O
ToonTalk	B-Language
preserves	O
the	O
order	O
of	O
the	O
messages	O
;	O
however	O
,	O
ToonTalk	B-Language
can	O
also	O
provide	O
an	O
indeterministic	O
merge	O
of	O
message	O
streams	O
.	O
</s>
