<s>
In	O
constraint	B-Application
satisfaction	I-Application
,	O
backmarking	B-Application
is	O
a	O
variant	O
of	O
the	O
backtracking	B-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
Backmarking	B-Application
works	O
like	O
backtracking	B-Algorithm
by	O
iteratively	O
evaluating	O
variables	O
in	O
a	O
given	O
order	O
,	O
for	O
example	O
,	O
.	O
</s>
<s>
It	O
improves	O
over	O
backtracking	B-Algorithm
by	O
maintaining	O
information	O
about	O
the	O
last	O
time	O
a	O
variable	O
was	O
instantiated	O
to	O
a	O
value	O
and	O
information	O
about	O
what	O
changed	O
since	O
then	O
.	O
</s>
<s>
In	O
particular	O
,	O
whenever	O
backtracking	B-Algorithm
would	O
set	O
,	O
backmarking	B-Application
compares	O
the	O
two	O
indexes	O
relative	O
to	O
and	O
the	O
pair	O
.	O
</s>
<s>
Contrary	O
to	O
other	O
variants	O
to	O
backtracking	B-Algorithm
,	O
backmarking	B-Application
does	O
not	O
reduce	O
the	O
search	O
space	O
but	O
only	O
possibly	O
reduce	O
the	O
number	O
of	O
constraints	O
that	O
are	O
satisfied	O
by	O
a	O
partial	O
solution	O
.	O
</s>
