<s>
In	O
distributed	B-Architecture
computing	I-Architecture
,	O
failure	B-Operating_System
semantics	I-Operating_System
is	O
used	O
to	O
describe	O
and	O
classify	O
errors	O
that	O
distributed	B-Architecture
systems	I-Architecture
can	O
experience	O
.	O
</s>
<s>
A	O
crash	B-General_Concept
error	I-General_Concept
is	O
when	O
nothing	O
happens	O
.	O
</s>
<s>
A	O
crash	B-General_Concept
is	O
a	O
special	O
case	O
of	O
omission	O
when	O
all	O
responses	O
fail	O
.	O
</s>
<s>
A	O
Timing	B-Operating_System
error	O
is	O
when	O
one	O
or	O
more	O
responses	O
arrive	O
outside	O
the	O
time	O
interval	O
specified	O
.	O
</s>
<s>
Timing	B-Operating_System
errors	O
can	O
be	O
early	O
or	O
late	O
.	O
</s>
<s>
An	O
omission	O
error	O
is	O
a	O
timing	B-Operating_System
error	O
when	O
a	O
response	O
has	O
infinite	O
timing	B-Operating_System
error	O
.	O
</s>
<s>
a	O
wrong	O
value	O
or	O
a	O
timing	B-Operating_System
error	O
)	O
.	O
</s>
<s>
When	O
a	O
client	O
uses	O
a	O
server	B-Application
it	O
can	O
cope	O
with	O
different	O
type	O
errors	O
from	O
the	O
server	B-Application
.	O
</s>
<s>
If	O
it	O
can	O
manage	O
a	O
crash	B-General_Concept
at	O
the	O
server	B-Application
it	O
is	O
said	O
to	O
assume	O
the	O
server	B-Application
to	O
have	O
crash	B-General_Concept
failure	B-Operating_System
semantics	I-Operating_System
.	O
</s>
<s>
If	O
it	O
can	O
manage	O
a	O
service	O
omission	O
it	O
is	O
said	O
to	O
assume	O
the	O
server	B-Application
to	O
have	O
omission	O
failure	B-Operating_System
semantics	I-Operating_System
.	O
</s>
<s>
Failure	B-Operating_System
semantics	I-Operating_System
are	O
the	O
type	O
of	O
errors	O
that	O
are	O
expected	O
to	O
appear	O
.	O
</s>
