<s>
D*	B-Algorithm
(	O
pronounced	O
"	O
D	O
star	O
"	O
)	O
is	O
any	O
one	O
of	O
the	O
following	O
three	O
related	O
incremental	B-Algorithm
search	I-Algorithm
algorithms	I-Algorithm
:	O
</s>
<s>
The	O
original	O
D*	B-Algorithm
,	O
by	O
Anthony	O
Stentz	O
,	O
is	O
an	O
informed	O
incremental	O
search	O
algorithm	O
.	O
</s>
<s>
Focused	O
D*	B-Algorithm
is	O
an	O
informed	O
incremental	B-Algorithm
heuristic	I-Algorithm
search	I-Algorithm
algorithm	O
by	O
Anthony	O
Stentz	O
that	O
combines	O
ideas	O
of	O
A*	B-Protocol
and	O
the	O
original	O
D*	B-Algorithm
.	O
</s>
<s>
Focused	O
D*	B-Algorithm
resulted	O
from	O
a	O
further	O
development	O
of	O
the	O
original	O
D*	B-Algorithm
.	O
</s>
<s>
D*	B-Algorithm
Lite	O
is	O
an	O
incremental	B-Algorithm
heuristic	I-Algorithm
search	I-Algorithm
algorithm	O
by	O
Sven	O
Koenig	O
and	O
Maxim	O
Likhachev	O
that	O
builds	O
on	O
LPA*	B-Algorithm
,	O
an	O
incremental	B-Algorithm
heuristic	I-Algorithm
search	I-Algorithm
algorithm	O
that	O
combines	O
ideas	O
of	O
A*	B-Protocol
and	O
Dynamic	O
SWSF-FP	O
.	O
</s>
<s>
Assuming	O
the	O
goal	O
coordinates	O
do	O
not	O
change	O
,	O
all	O
three	O
search	O
algorithms	O
are	O
more	O
efficient	O
than	O
repeated	O
A*	B-Protocol
searches	I-Protocol
.	O
</s>
<s>
D*	B-Algorithm
and	O
its	O
variants	O
have	O
been	O
widely	O
used	O
for	O
mobile	O
robot	O
and	O
autonomous	O
vehicle	O
navigation	O
.	O
</s>
<s>
Current	O
systems	O
are	O
typically	O
based	O
on	O
D*	B-Algorithm
Lite	O
rather	O
than	O
the	O
original	O
D*	B-Algorithm
or	O
Focused	O
D*	B-Algorithm
.	O
</s>
<s>
In	O
fact	O
,	O
even	O
Stentz	O
's	O
lab	O
uses	O
D*	B-Algorithm
Lite	O
rather	O
than	O
D*	B-Algorithm
in	O
some	O
implementations	O
.	O
</s>
<s>
The	O
original	O
D*	B-Algorithm
was	O
introduced	O
by	O
Anthony	O
Stentz	O
in	O
1994	O
.	O
</s>
<s>
The	O
name	O
D*	B-Algorithm
comes	O
from	O
the	O
term	O
"	O
Dynamic	O
A*	B-Protocol
"	O
,	O
because	O
the	O
algorithm	O
behaves	O
like	O
A*	B-Protocol
except	O
that	O
the	O
arc	O
costs	O
can	O
change	O
as	O
the	O
algorithm	O
runs	O
.	O
</s>
<s>
The	O
basic	O
operation	O
of	O
D*	B-Algorithm
is	O
outlined	O
below	O
.	O
</s>
<s>
Like	O
Dijkstra	O
's	O
algorithm	O
and	O
A*	B-Protocol
,	O
D*	B-Algorithm
maintains	O
a	O
list	O
of	O
nodes	O
to	O
be	O
evaluated	O
,	O
known	O
as	O
the	O
"	O
OPEN	O
list	O
"	O
.	O
</s>
<s>
In	O
contrast	O
to	O
canonical	O
A*	B-Protocol
,	O
which	O
follows	O
the	O
path	O
from	O
start	O
to	O
finish	O
,	O
D*	B-Algorithm
begins	O
by	O
searching	O
backwards	O
from	O
the	O
goal	O
node	O
.	O
</s>
<s>
This	O
means	O
that	O
the	O
algorithm	O
is	O
actually	O
computing	O
the	O
A*	B-Protocol
optimal	O
path	O
for	O
every	O
possible	O
start	O
node	O
.	O
</s>
<s>
These	O
waves	O
of	O
RAISE	O
and	O
LOWER	O
states	O
are	O
the	O
heart	O
of	O
D*	B-Algorithm
.	O
</s>
<s>
As	O
its	O
name	O
suggests	O
,	O
Focused	O
D*	B-Algorithm
is	O
an	O
extension	O
of	O
D*	B-Algorithm
which	O
uses	O
a	O
heuristic	O
to	O
focus	O
the	O
propagation	O
of	O
RAISE	O
and	O
LOWER	O
toward	O
the	O
robot	O
.	O
</s>
<s>
In	O
this	O
way	O
,	O
only	O
the	O
states	O
that	O
matter	O
are	O
updated	O
,	O
in	O
the	O
same	O
way	O
that	O
A*	B-Protocol
only	O
computes	O
costs	O
for	O
some	O
of	O
the	O
nodes	O
.	O
</s>
<s>
D*	B-Algorithm
Lite	O
is	O
not	O
based	O
on	O
the	O
original	O
D*	B-Algorithm
or	O
Focused	O
D*	B-Algorithm
,	O
but	O
implements	O
the	O
same	O
behavior	O
.	O
</s>
<s>
It	O
is	O
simpler	O
to	O
understand	O
and	O
can	O
be	O
implemented	O
in	O
fewer	O
lines	O
of	O
code	O
,	O
hence	O
the	O
name	O
"	O
D*	B-Algorithm
Lite	O
"	O
.	O
</s>
<s>
Performance-wise	O
,	O
it	O
is	O
as	O
good	O
as	O
or	O
better	O
than	O
Focused	O
D*	B-Algorithm
.	O
</s>
<s>
D*	B-Algorithm
Lite	O
is	O
based	O
on	O
Lifelong	B-Algorithm
Planning	I-Algorithm
A*	I-Algorithm
,	O
which	O
was	O
introduced	O
by	O
Koenig	O
and	O
Likhachev	O
few	O
years	O
earlier	O
.	O
</s>
<s>
For	O
D*	B-Algorithm
,	O
it	O
is	O
important	O
to	O
distinguish	O
between	O
current	O
and	O
minimum	O
costs	O
.	O
</s>
