<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
the	O
Actor	B-Application
model	I-Application
,	O
first	O
published	O
in	O
1973	O
,	O
is	O
a	O
mathematical	O
model	O
of	O
concurrent	B-Architecture
computation	I-Architecture
.	O
</s>
<s>
This	O
article	O
reports	O
on	O
the	O
middle	O
history	O
of	O
the	O
Actor	B-Application
model	I-Application
in	O
which	O
major	O
themes	O
were	O
initial	O
implementations	O
,	O
initial	O
applications	O
,	O
and	O
development	O
of	O
the	O
first	O
proof	O
theory	O
and	O
denotational	O
model	O
.	O
</s>
<s>
It	O
is	O
the	O
follow	O
on	O
article	O
to	O
Actor	B-Application
model	I-Application
early	O
history	O
which	O
reports	O
on	O
the	O
early	O
history	O
of	O
the	O
Actor	B-Application
model	I-Application
which	O
concerned	O
the	O
basic	O
development	O
of	O
the	O
concepts	O
.	O
</s>
<s>
The	O
article	O
Actor	B-Application
model	I-Application
later	I-Application
history	I-Application
reports	O
on	O
developments	O
after	O
the	O
ones	O
reported	O
in	O
this	O
article	O
.	O
</s>
<s>
In	O
his	O
doctoral	O
dissertation	O
,	O
Aki	O
Yonezawa	O
developed	O
further	O
techniques	O
for	O
proving	O
properties	O
of	O
Actor	B-Application
systems	I-Application
including	O
those	O
that	O
make	O
use	O
of	O
migration	O
.	O
</s>
<s>
Garbage	B-General_Concept
collection	I-General_Concept
(	O
the	O
automatic	O
reclamation	O
of	O
unused	O
storage	O
)	O
was	O
an	O
important	O
theme	O
in	O
the	O
development	O
of	O
the	O
Actor	B-Application
model	I-Application
.	O
</s>
<s>
In	O
his	O
doctoral	O
dissertation	O
,	O
Peter	O
Bishop	O
developed	O
an	O
algorithm	O
for	O
garbage	B-General_Concept
collection	I-General_Concept
in	O
distributed	O
systems	O
.	O
</s>
<s>
Cyclic	O
structures	O
were	O
collected	O
by	O
incrementally	O
migrating	O
Actors	O
(	O
objects	O
)	O
onto	O
other	O
systems	O
which	O
had	O
their	O
addresses	O
until	O
a	O
cyclic	O
structure	O
was	O
entirely	O
contained	O
in	O
a	O
single	O
system	O
where	O
the	O
garbage	B-General_Concept
collector	I-General_Concept
could	O
recover	O
the	O
storage	O
.	O
</s>
<s>
Henry	O
Baker	O
developed	O
an	O
algorithm	O
for	O
real-time	O
garbage	B-General_Concept
collection	I-General_Concept
in	O
his	O
doctoral	O
dissertation	O
.	O
</s>
<s>
See	O
incremental	O
garbage	B-General_Concept
collection	I-General_Concept
.	O
</s>
<s>
Henry	O
Lieberman	O
and	O
Carl	O
Hewitt	O
 [ 1983 ] 	O
developed	O
a	O
real	O
time	O
garbage	B-General_Concept
collection	I-General_Concept
based	O
on	O
the	O
lifetimes	O
of	O
Actors	O
(	O
Objects	O
)	O
.	O
</s>
<s>
The	O
fundamental	O
idea	O
was	O
to	O
allocate	O
Actors	O
(	O
objects	O
)	O
in	O
generations	O
so	O
that	O
only	O
the	O
latest	O
generations	O
would	O
have	O
to	O
be	O
examined	O
during	O
a	O
garbage	B-General_Concept
collection	I-General_Concept
.	O
</s>
<s>
See	O
generational	O
garbage	B-General_Concept
collection	I-General_Concept
.	O
</s>
<s>
Bill	O
Kornfeld	O
developed	O
the	O
Ether	O
programming	O
language	O
for	O
the	O
Scientific	B-Application
Community	I-Application
Metaphor	I-Application
in	O
his	O
doctoral	O
dissertation	O
.	O
</s>
<s>
This	O
gave	O
rise	O
to	O
the	O
so-called	O
inheritance	O
anomaly	O
controversy	O
in	O
object-oriented	O
concurrent	B-Architecture
programming	I-Architecture
languages	O
[	O
Satoshi	O
Matsuoka	O
and	O
Aki	O
Yonezawa	O
1993	O
,	O
Giuseppe	O
Milicia	O
and	O
Vladimiro	O
Sassone	O
2004 ]	O
.	O
</s>
<s>
In	O
his	O
doctoral	O
dissertation	O
,	O
Will	O
Clinger	O
developed	O
the	O
first	O
denotational	O
model	O
of	O
Actor	B-Application
systems	I-Application
.	O
</s>
<s>
See	O
denotational	B-Application
semantics	I-Application
of	I-Application
the	I-Application
Actor	I-Application
model	I-Application
.	O
</s>
