<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
B*	B-Protocol
(	O
pronounced	O
"	O
B	O
star	O
"	O
)	O
is	O
a	O
best-first	B-Algorithm
graph	O
search	O
algorithm	O
that	O
finds	O
the	O
least-cost	O
path	O
from	O
a	O
given	O
initial	O
node	O
to	O
any	O
goal	B-Algorithm
node	I-Algorithm
(	O
out	O
of	O
one	O
or	O
more	O
possible	O
goals	O
)	O
.	O
</s>
<s>
First	O
published	O
by	O
Hans	O
Berliner	O
in	O
1979	O
,	O
it	O
is	O
related	O
to	O
the	O
A*	B-Protocol
search	I-Protocol
algorithm	I-Protocol
.	O
</s>
<s>
Leaf	O
nodes	O
of	O
a	O
B*	B-Protocol
-tree	O
are	O
given	O
evaluations	O
that	O
are	O
intervals	O
rather	O
than	O
single	O
numbers	O
.	O
</s>
<s>
If	O
all	O
intervals	O
attached	O
to	O
leaf	O
nodes	O
satisfy	O
this	O
property	O
,	O
then	O
B*	B-Protocol
will	O
identify	O
an	O
optimal	O
path	O
to	O
the	O
goal	O
state	O
.	O
</s>
<s>
B*	B-Protocol
systematically	O
expands	O
nodes	O
in	O
order	O
to	O
create	O
"	O
separation	O
,	O
"	O
which	O
occurs	O
when	O
the	O
lower	O
bound	O
of	O
a	O
direct	O
child	O
of	O
the	O
root	O
is	O
at	O
least	O
as	O
large	O
as	O
the	O
upper	O
bound	O
of	O
any	O
other	O
direct	O
child	O
of	O
the	O
root	O
.	O
</s>
<s>
B*	B-Protocol
is	O
a	O
best-first	B-Algorithm
process	O
,	O
which	O
means	O
that	O
it	O
is	O
very	O
efficient	O
to	O
traverse	O
the	O
tree	O
,	O
repeatedly	O
descending	O
to	O
find	O
a	O
leaf	O
to	O
expand	O
.	O
</s>
<s>
If	O
intervals	O
are	O
incorrect	O
(	O
in	O
the	O
sense	O
that	O
the	O
game-theoretic	O
value	O
of	O
the	O
node	O
is	O
not	O
contained	O
within	O
the	O
interval	O
)	O
,	O
then	O
B*	B-Protocol
might	O
not	O
be	O
able	O
to	O
identify	O
the	O
correct	O
path	O
.	O
</s>
<s>
The	O
Maven	B-General_Concept
(	O
Scrabble	O
)	O
program	O
has	O
an	O
innovation	O
that	O
improves	O
the	O
robustness	O
of	O
B*	B-Protocol
when	O
evaluation	O
errors	O
are	O
possible	O
.	O
</s>
<s>
If	O
a	O
search	O
terminates	O
due	O
to	O
separation	O
then	O
Maven	B-General_Concept
restarts	O
the	O
search	O
after	O
widening	O
all	O
of	O
the	O
evaluation	O
intervals	O
by	O
a	O
small	O
amount	O
.	O
</s>
<s>
The	O
B*	B-Protocol
algorithm	I-Protocol
applies	O
to	O
two-player	O
deterministic	O
zero-sum	O
games	O
.	O
</s>
<s>
Andrew	O
Palay	O
applied	O
B*	B-Protocol
to	O
chess	O
.	O
</s>
<s>
There	O
is	O
no	O
report	O
of	O
how	O
well	O
this	O
system	O
performed	O
compared	O
to	O
alpha-beta	B-Algorithm
pruning	I-Algorithm
search	O
engines	O
running	O
on	O
the	O
same	O
hardware	O
.	O
</s>
<s>
The	O
Maven	B-General_Concept
(	O
Scrabble	O
)	O
program	O
applied	O
B*	B-Protocol
search	I-Protocol
to	O
endgames	O
.	O
</s>
<s>
The	O
B*	B-Protocol
search	I-Protocol
algorithm	I-Protocol
has	O
been	O
used	O
to	O
compute	O
optimal	O
strategy	O
in	O
a	O
sum	O
game	O
of	O
a	O
set	O
of	O
combinatorial	O
games	O
.	O
</s>
