<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
an	O
online	B-Algorithm
algorithm	I-Algorithm
measures	O
its	O
competitiveness	B-Algorithm
against	O
different	O
adversary	B-Algorithm
models	I-Algorithm
.	O
</s>
<s>
For	O
deterministic	O
algorithms	O
,	O
the	O
adversary	B-Algorithm
is	O
the	O
same	O
as	O
the	O
adaptive	O
offline	O
adversary	B-Algorithm
.	O
</s>
<s>
For	O
randomized	O
online	B-Algorithm
algorithms	I-Algorithm
competitiveness	B-Algorithm
can	O
depend	O
upon	O
the	O
adversary	B-Algorithm
model	I-Algorithm
used	O
.	O
</s>
<s>
The	O
three	O
common	O
adversaries	B-Algorithm
are	O
the	O
oblivious	O
adversary	B-Algorithm
,	O
the	O
adaptive	O
online	O
adversary	B-Algorithm
,	O
and	O
the	O
adaptive	O
offline	O
adversary	B-Algorithm
.	O
</s>
<s>
The	O
oblivious	O
adversary	B-Algorithm
is	O
sometimes	O
referred	O
to	O
as	O
the	O
weak	O
adversary	B-Algorithm
.	O
</s>
<s>
This	O
adversary	B-Algorithm
knows	O
the	O
algorithm	O
's	O
code	O
,	O
but	O
does	O
not	O
get	O
to	O
know	O
the	O
randomized	O
results	O
of	O
the	O
algorithm	O
.	O
</s>
<s>
The	O
adaptive	O
online	O
adversary	B-Algorithm
is	O
sometimes	O
called	O
the	O
medium	O
adversary	B-Algorithm
.	O
</s>
<s>
This	O
adversary	B-Algorithm
must	O
make	O
its	O
own	O
decision	O
before	O
it	O
is	O
allowed	O
to	O
know	O
the	O
decision	O
of	O
the	O
algorithm	O
.	O
</s>
<s>
The	O
adaptive	O
offline	O
adversary	B-Algorithm
is	O
sometimes	O
called	O
the	O
strong	O
adversary	B-Algorithm
.	O
</s>
<s>
This	O
adversary	B-Algorithm
knows	O
everything	O
,	O
even	O
the	O
random	O
number	O
generator	O
.	O
</s>
<s>
This	O
adversary	B-Algorithm
is	O
so	O
strong	O
that	O
randomization	O
does	O
not	O
help	O
against	O
it	O
.	O
</s>
<s>
If	O
there	O
is	O
a	O
randomized	O
algorithm	O
that	O
is	O
α-competitive	O
against	O
any	O
adaptive	O
offline	O
adversary	B-Algorithm
then	O
there	O
also	O
exists	O
an	O
α-competitive	O
deterministic	O
algorithm	O
.	O
</s>
<s>
If	O
G	O
is	O
a	O
c-competitive	O
randomized	O
algorithm	O
against	O
any	O
adaptive	O
online	O
adversary	B-Algorithm
,	O
and	O
there	O
is	O
a	O
randomized	O
d-competitive	O
algorithm	O
against	O
any	O
oblivious	O
adversary	B-Algorithm
,	O
then	O
G	O
is	O
a	O
randomized	O
(	O
c	O
*	O
d	O
)	O
-competitive	O
algorithm	O
against	O
any	O
adaptive	O
offline	O
adversary	B-Algorithm
.	O
</s>
