<s>
The	O
Sussman	B-Application
anomaly	I-Application
is	O
a	O
problem	O
in	O
artificial	B-Application
intelligence	I-Application
,	O
first	O
described	O
by	O
Gerald	O
Sussman	O
,	O
that	O
illustrates	O
a	O
weakness	O
of	O
noninterleaved	O
planning	B-Application
algorithms	I-Application
,	O
which	O
were	O
prominent	O
in	O
the	O
early	O
1970s	O
.	O
</s>
<s>
The	O
agent	O
must	O
stack	O
the	O
blocks	O
such	O
that	O
A	B-Application
is	I-Application
atop	O
B	O
,	O
which	O
in	O
turn	O
is	O
atop	O
C	O
.	O
However	O
,	O
it	O
may	O
only	O
move	O
one	O
block	O
at	O
a	O
time	O
.	O
</s>
<s>
Sussman	O
(	O
and	O
his	O
supervisor	O
,	O
Marvin	O
Minsky	O
)	O
believed	O
that	O
intelligence	O
requires	O
a	O
list	O
of	O
exceptions	O
or	O
tricks	O
,	O
and	O
developed	O
a	O
modular	B-Architecture
planning	O
system	O
for	O
"	O
debugging	O
"	O
plans	O
.	O
</s>
