<s>
In	O
knowledge-based	B-General_Concept
systems	I-General_Concept
,	O
agents	O
choose	O
actions	O
based	O
on	O
the	O
principle	B-General_Concept
of	I-General_Concept
rationality	I-General_Concept
to	O
move	O
closer	O
to	O
a	O
desired	O
goal	O
.	O
</s>
<s>
The	O
agent	O
is	O
able	O
to	O
make	O
decisions	O
based	O
on	O
knowledge	O
it	O
has	O
about	O
the	O
world	O
(	O
see	O
knowledge	B-General_Concept
level	I-General_Concept
)	O
.	O
</s>
<s>
This	O
level	O
of	O
description	O
for	O
the	O
agent	O
's	O
behavior	O
is	O
the	O
symbol	B-General_Concept
level	I-General_Concept
.	O
</s>
<s>
For	O
example	O
,	O
in	O
a	O
computer	O
program	O
,	O
the	O
knowledge	B-General_Concept
level	I-General_Concept
consists	O
of	O
the	O
information	O
contained	O
in	O
its	O
data	O
structures	O
that	O
it	O
uses	O
to	O
perform	O
certain	O
actions	O
.	O
</s>
<s>
The	O
symbol	B-General_Concept
level	I-General_Concept
consists	O
of	O
the	O
program	O
's	O
algorithms	O
,	O
the	O
data	O
structures	O
themselves	O
,	O
and	O
so	O
on	O
.	O
</s>
