<s>
Opportunistic	B-General_Concept
reasoning	I-General_Concept
is	O
a	O
method	O
of	O
selecting	O
a	O
suitable	O
logical	O
inference	O
strategy	O
within	O
artificial	B-Application
intelligence	I-Application
applications	O
.	O
</s>
<s>
However	O
,	O
in	O
opportunistic	B-General_Concept
reasoning	I-General_Concept
,	O
pieces	O
of	O
knowledge	O
may	O
be	O
applied	O
either	O
forward	O
or	O
backward	O
,	O
at	O
the	O
"	O
most	O
opportune	O
time	O
"	O
.	O
</s>
<s>
An	O
opportunistic	B-General_Concept
reasoning	I-General_Concept
system	O
may	O
combine	O
elements	O
of	O
both	O
forward	O
and	O
backward	O
reasoning	O
.	O
</s>
<s>
Opportunistic	B-General_Concept
reasoning	I-General_Concept
has	O
been	O
used	O
in	O
applications	O
such	O
as	O
blackboard	B-General_Concept
systems	I-General_Concept
and	O
medical	O
applications	O
.	O
</s>
