<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
an	O
interchangeability	B-Application
algorithm	I-Application
is	O
a	O
technique	O
used	O
to	O
more	O
efficiently	O
solve	O
constraint	B-Application
satisfaction	I-Application
problems	I-Application
(	O
CSP	O
)	O
.	O
</s>
<s>
If	O
two	O
variables	O
A	O
and	O
B	O
in	O
a	O
CSP	O
may	O
be	O
swapped	O
for	O
each	O
other	O
(	O
that	O
is	O
,	O
A	B-Application
is	I-Application
replaced	O
by	O
B	O
and	O
B	O
is	O
replaced	O
by	O
A	O
)	O
without	O
changing	O
the	O
nature	O
of	O
the	O
problem	O
or	O
its	O
solutions	O
,	O
then	O
A	O
and	O
B	O
are	O
interchangeable	O
variables	O
.	O
</s>
<s>
The	O
concept	O
of	O
interchangeability	B-Application
and	O
the	O
interchangeability	B-Application
algorithm	I-Application
in	O
constraint	B-Application
satisfaction	I-Application
problems	I-Application
was	O
first	O
introduced	O
by	O
Eugene	O
Freuder	O
in	O
1991	O
.	O
</s>
<s>
The	O
interchangeability	B-Application
algorithm	I-Application
reduces	O
the	O
search	O
space	O
of	O
backtracking	B-Algorithm
search	I-Algorithm
algorithms	O
,	O
thereby	O
improving	O
the	O
efficiency	O
of	O
NP-complete	O
CSP	O
problems	O
.	O
</s>
<s>
The	O
algorithm	O
can	O
be	O
used	O
to	O
explicitly	O
find	O
solutions	O
to	O
a	O
constraint	B-Application
satisfaction	I-Application
problem	I-Application
.	O
</s>
<s>
In	O
Computer	B-General_Concept
Science	I-General_Concept
,	O
the	O
interchangeability	B-Application
algorithm	I-Application
has	O
been	O
extensively	O
used	O
in	O
the	O
fields	O
of	O
artificial	B-Application
intelligence	I-Application
,	O
graph	O
coloring	O
problems	O
,	O
abstraction	O
frame-works	O
and	O
solution	O
adaptation	O
.	O
</s>
