<s>
For	O
parsing	B-Language
algorithms	I-Language
in	O
computer	B-General_Concept
science	I-General_Concept
,	O
the	O
inside	B-Application
–	I-Application
outside	I-Application
algorithm	I-Application
is	O
a	O
way	O
of	O
re-estimating	O
production	O
probabilities	O
in	O
a	O
probabilistic	B-General_Concept
context-free	I-General_Concept
grammar	I-General_Concept
.	O
</s>
<s>
It	O
was	O
introduced	O
by	O
James	O
K	O
.	O
Baker	O
in	O
1979	O
as	O
a	O
generalization	O
of	O
the	O
forward	B-Algorithm
–	I-Algorithm
backward	I-Algorithm
algorithm	I-Algorithm
for	O
parameter	O
estimation	O
on	O
hidden	O
Markov	O
models	O
to	O
stochastic	B-General_Concept
context-free	I-General_Concept
grammars	I-General_Concept
.	O
</s>
<s>
It	O
is	O
used	O
to	O
compute	O
expectations	O
,	O
for	O
example	O
as	O
part	O
of	O
the	O
expectation	B-Algorithm
–	I-Algorithm
maximization	I-Algorithm
algorithm	I-Algorithm
(	O
an	O
unsupervised	O
learning	O
algorithm	O
)	O
.	O
</s>
