<s>
N-version	B-General_Concept
programming	I-General_Concept
(	O
NVP	O
)	O
,	O
also	O
known	O
as	O
multiversion	B-General_Concept
programming	I-General_Concept
or	O
multiple-version	O
dissimilar	O
software	O
,	O
is	O
a	O
method	O
or	O
process	O
in	O
software	B-General_Concept
engineering	I-General_Concept
where	O
multiple	O
functionally	O
equivalent	O
programs	O
are	O
independently	O
generated	O
from	O
the	O
same	O
initial	O
specifications	O
.	O
</s>
<s>
The	O
concept	O
of	O
N-version	B-General_Concept
programming	I-General_Concept
was	O
introduced	O
in	O
1977	O
by	O
Liming	O
Chen	O
and	O
Algirdas	O
Avizienis	O
with	O
the	O
central	O
conjecture	O
that	O
the	O
"	O
independence	O
of	O
programming	O
efforts	O
will	O
greatly	O
reduce	O
the	O
probability	O
of	O
identical	O
software	O
faults	O
occurring	O
in	O
two	O
or	O
more	O
versions	O
of	O
the	O
program	O
"	O
.	O
</s>
<s>
The	O
aim	O
of	O
NVP	O
is	O
to	O
improve	O
the	O
reliability	O
of	O
software	O
operation	O
by	O
building	O
in	O
fault	B-General_Concept
tolerance	I-General_Concept
or	O
redundancy	B-Application
.	O
</s>
<s>
The	O
general	O
steps	O
of	O
N-version	B-General_Concept
programming	I-General_Concept
are	O
:	O
</s>
<s>
“	O
There	O
has	O
been	O
considerable	O
debate	O
as	O
to	O
realizing	O
the	O
full	O
potential	O
from	O
n-version	B-General_Concept
programming	I-General_Concept
as	O
it	O
makes	O
the	O
assumption	O
that	O
the	O
independence	O
will	O
lead	O
to	O
statistically	O
independent	O
mistakes	O
.	O
</s>
<s>
N-version	B-General_Concept
programming	I-General_Concept
has	O
been	O
applied	O
to	O
software	O
in	O
switching	O
trains	O
,	O
performing	O
flight	O
control	O
computations	O
on	O
modern	O
airliners	O
,	O
electronic	O
voting	O
(	O
the	O
SAVE	O
System	O
)	O
,	O
and	O
the	O
detection	O
of	O
zero-day	O
exploits	O
,	O
among	O
other	O
uses	O
.	O
</s>
