<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
program	B-Application
derivation	I-Application
is	O
the	O
derivation	O
of	O
a	O
program	O
from	O
its	O
specification	B-Application
,	O
by	O
mathematical	O
means	O
.	O
</s>
<s>
To	O
derive	O
a	O
program	O
means	O
to	O
write	O
a	O
formal	B-Application
specification	I-Application
,	O
which	O
is	O
usually	O
non-executable	O
,	O
and	O
then	O
apply	O
mathematically	O
correct	O
rules	O
in	O
order	O
to	O
obtain	O
an	O
executable	O
program	O
satisfying	O
that	O
specification	B-Application
.	O
</s>
<s>
The	O
approach	O
usually	O
taken	O
in	O
formal	O
verification	O
is	O
to	O
first	O
write	O
a	O
program	O
,	O
and	O
then	O
provide	O
a	O
proof	O
that	O
it	O
conforms	O
to	O
a	O
given	O
specification	B-Application
.	O
</s>
<s>
making	O
design	O
decisions	O
through	O
formal	O
manipulation	O
of	O
the	O
specification	B-Application
.	O
</s>
<s>
Terms	O
that	O
are	O
roughly	O
synonymous	O
with	O
program	B-Application
derivation	I-Application
are	O
:	O
transformational	O
programming	O
,	O
algorithmics	O
,	O
deductive	O
programming	O
.	O
</s>
<s>
The	O
Bird-Meertens	B-Application
Formalism	I-Application
is	O
an	O
approach	O
to	O
program	B-Application
derivation	I-Application
.	O
</s>
