<s>
In	O
software	B-General_Concept
engineering	I-General_Concept
,	O
software	B-Application
system	I-Application
safety	I-Application
optimizes	O
system	O
safety	O
in	O
the	O
design	O
,	O
development	O
,	O
use	O
,	O
and	O
maintenance	O
of	O
software	O
systems	O
and	O
their	O
integration	O
with	O
safety-critical	B-Application
hardware	O
systems	O
in	O
an	O
operational	O
environment	O
.	O
</s>
<s>
Software	B-Application
system	I-Application
safety	I-Application
is	O
a	O
subset	O
of	O
system	O
safety	O
and	O
system	O
engineering	O
and	O
is	O
synonymous	O
with	O
the	O
software	B-General_Concept
engineering	I-General_Concept
aspects	O
of	O
Functional	O
Safety	O
.	O
</s>
<s>
Both	O
simple	O
and	O
highly	O
integrated	O
multiple	O
systems	O
are	O
experiencing	O
an	O
extraordinary	O
growth	O
in	O
the	O
use	O
of	O
computers	O
and	O
software	O
to	O
monitor	O
and/or	O
control	O
safety-critical	B-Application
subsystems	O
or	O
functions	O
.	O
</s>
<s>
A	O
software	B-Application
specification	I-Application
error	O
,	O
design	O
flaw	O
,	O
or	O
the	O
lack	O
of	O
generic	O
safety-critical	B-Application
requirements	O
can	O
contribute	O
to	O
or	O
cause	O
a	O
system	O
failure	O
or	O
erroneous	O
human	O
decision	O
.	O
</s>
<s>
To	O
achieve	O
an	O
acceptable	O
level	O
of	O
safety	O
for	O
software	O
used	O
in	O
critical	O
applications	O
,	O
software	B-Application
system	I-Application
safety	I-Application
engineering	O
must	O
be	O
given	O
primary	O
emphasis	O
early	O
in	O
the	O
requirements	O
definition	O
and	O
system	O
conceptual	O
design	O
process	O
.	O
</s>
<s>
Safety-critical	B-Application
software	O
must	O
then	O
receive	O
continuous	O
management	O
emphasis	O
and	O
engineering	O
analysis	O
throughout	O
the	O
development	O
and	O
operational	O
lifecycles	O
of	O
the	O
system	O
.	O
</s>
<s>
Functional	O
Hazard	O
Analyses	O
(	O
FHA	O
)	O
are	O
often	O
conducted	O
early	O
on	O
-	O
in	O
parallel	O
with	O
or	O
as	O
part	O
of	O
system	O
engineering	O
Functional	O
Analyses	O
-	O
to	O
determine	O
the	O
safety-critical	B-Application
functions	O
(	O
SCF	O
)	O
of	O
the	O
systems	O
for	O
further	O
analyses	O
and	O
verification	O
.	O
</s>
<s>
Software	B-Application
system	I-Application
safety	I-Application
is	O
directly	O
related	O
to	O
the	O
more	O
critical	O
design	O
aspects	O
and	O
safety	O
attributes	O
in	O
software	O
and	O
system	O
functionality	O
,	O
whereas	O
software	O
quality	O
attributes	O
are	O
inherently	O
different	O
and	O
require	O
standard	O
scrutiny	O
and	O
development	O
rigor	O
.	O
</s>
<s>
Once	O
these	O
"	O
functional	O
"	O
software	O
safety	O
analyses	O
are	O
completed	O
the	O
software	B-General_Concept
engineering	I-General_Concept
team	O
will	O
know	O
where	O
to	O
place	O
safety	O
emphasis	O
and	O
what	O
functional	O
threads	O
,	O
functional	O
paths	O
,	O
domains	O
and	O
boundaries	O
to	O
focus	O
on	O
when	O
designing	O
in	O
software	O
safety	O
attributes	O
to	O
ensure	O
correct	O
functionality	O
and	O
to	O
detect	O
malfunctions	O
,	O
failures	O
,	O
faults	O
and	O
to	O
implement	O
a	O
host	O
of	O
mitigation	O
strategies	O
to	O
control	O
hazards	O
.	O
</s>
<s>
On	O
complex	O
systems	O
involving	O
many	O
interactions	O
safety-critical	B-Application
functionality	O
should	O
be	O
identified	O
and	O
thoroughly	O
analyzed	O
before	O
deriving	O
hazards	O
and	O
design	O
safeguards	O
for	O
mitigations	O
.	O
</s>
<s>
Safety-critical	B-Application
functions	O
lists	O
and	O
preliminary	O
hazards	O
lists	O
should	O
be	O
determined	O
proactively	O
and	O
influence	O
the	O
requirements	O
that	O
will	O
be	O
implemented	O
in	O
software	O
.	O
</s>
<s>
The	O
number	O
and	O
complexity	O
of	O
safety	B-Application
critical	I-Application
interfaces	O
is	O
minimized	O
.	O
</s>
<s>
The	O
number	O
and	O
complexity	O
of	O
safety	B-Application
critical	I-Application
computer	O
software	O
components	O
is	O
minimized	O
.	O
</s>
<s>
Sound	O
software	B-General_Concept
engineering	I-General_Concept
practices	O
and	O
documentation	O
are	O
used	O
in	O
the	O
development	O
of	O
the	O
software	O
.	O
</s>
<s>
Software	O
with	O
safety-critical	B-Application
functionality	O
must	O
be	O
thoroughly	O
verified	O
with	O
objective	O
analysis	O
and	O
preferably	O
test	O
evidence	O
that	O
all	O
safety	O
requirements	O
have	O
been	O
met	O
per	O
established	O
criteria	O
.	O
</s>
