<s>
As	O
a	O
subfield	O
in	O
artificial	B-Application
intelligence	I-Application
,	O
diagnosis	O
is	O
concerned	O
with	O
the	O
development	O
of	O
algorithms	O
and	O
techniques	O
that	O
are	O
able	O
to	O
determine	O
whether	O
the	O
behaviour	O
of	O
a	O
system	O
is	O
correct	O
.	O
</s>
<s>
The	O
expert	O
diagnosis	O
(	O
or	O
diagnosis	O
by	O
expert	B-Application
system	I-Application
)	O
is	O
based	O
on	O
experience	O
with	O
the	O
system	O
.	O
</s>
<s>
The	O
off-line	O
process	O
of	O
building	O
an	O
expert	B-Application
system	I-Application
can	O
require	O
a	O
large	O
amount	O
of	O
time	O
and	O
computer	O
memory	O
.	O
</s>
<s>
The	O
size	O
of	O
the	O
final	O
expert	B-Application
system	I-Application
.	O
</s>
<s>
As	O
the	O
expert	B-Application
system	I-Application
aims	O
to	O
map	O
any	O
observation	O
to	O
a	O
diagnosis	O
,	O
it	O
will	O
in	O
some	O
cases	O
require	O
a	O
huge	O
amount	O
of	O
storage	O
space	O
.	O
</s>
<s>
If	O
even	O
a	O
small	O
modification	O
is	O
made	O
on	O
the	O
system	O
,	O
the	O
process	O
of	O
constructing	O
the	O
expert	B-Application
system	I-Application
must	O
be	O
repeated	O
.	O
</s>
<s>
A	O
slightly	O
different	O
approach	O
is	O
to	O
build	O
an	O
expert	B-Application
system	I-Application
from	O
a	O
model	O
of	O
the	O
system	O
rather	O
than	O
directly	O
from	O
an	O
expertise	O
.	O
</s>
<s>
This	O
approach	O
can	O
be	O
seen	O
as	O
model-based	O
,	O
but	O
it	O
benefits	O
from	O
some	O
advantages	O
and	O
suffers	O
some	O
drawbacks	O
of	O
the	O
expert	B-Application
system	I-Application
approach	O
.	O
</s>
