<s>
GOAL	O
is	O
an	O
agent	O
programming	O
language	O
for	O
programming	O
cognitive	B-Protocol
agents	I-Protocol
.	O
</s>
<s>
The	O
language	O
provides	O
the	O
basic	O
building	O
blocks	O
to	O
design	O
and	O
implement	O
cognitive	B-Protocol
agents	I-Protocol
by	O
programming	O
constructs	O
that	O
allow	O
and	O
facilitate	O
the	O
manipulation	O
of	O
an	O
agent	O
's	O
beliefs	O
and	O
goals	O
and	O
to	O
structure	O
its	O
decision-making	O
.	O
</s>
<s>
Declarative	B-Language
beliefs	O
:	O
Agents	O
use	O
a	O
symbolic	O
,	O
logical	O
language	O
to	O
represent	O
the	O
information	O
they	O
have	O
,	O
and	O
their	O
beliefs	O
or	O
knowledge	O
about	O
the	O
environment	O
they	O
act	O
upon	O
in	O
order	O
to	O
achieve	O
their	O
goals	O
.	O
</s>
<s>
Declarative	B-Language
goals	O
:	O
Agents	O
may	O
have	O
multiple	O
goals	O
that	O
specify	O
what	O
the	O
agent	O
wants	O
to	O
achieve	O
at	O
some	O
moment	O
in	O
the	O
near	O
or	O
distant	O
future	O
.	O
</s>
<s>
Declarative	B-Language
goals	O
specify	O
a	O
state	O
of	O
the	O
environment	O
that	O
the	O
agent	O
wants	O
to	O
establish	O
,	O
they	O
do	O
not	O
specify	O
actions	O
or	O
procedures	O
how	O
to	O
achieve	O
such	O
states	O
.	O
</s>
<s>
Cognitive	B-Protocol
agents	I-Protocol
are	O
assumed	O
to	O
not	O
have	O
goals	O
that	O
they	O
believe	O
are	O
already	O
achieved	O
,	O
a	O
constraint	O
which	O
has	O
been	O
built	O
into	O
GOAL	O
agents	O
by	O
dropping	O
a	O
goal	O
when	O
it	O
has	O
been	O
completely	O
achieved	O
.	O
</s>
<s>
Communication	O
at	O
the	O
knowledge	B-General_Concept
level	I-General_Concept
:	O
Agents	O
may	O
communicate	O
with	O
each	O
other	O
to	O
exchange	O
information	O
,	O
and	O
to	O
coordinate	O
their	O
actions	O
.	O
</s>
<s>
The	O
knowledge	O
,	O
beliefs	O
and	O
goals	O
are	O
represented	O
in	O
a	O
knowledge	O
representation	O
language	O
such	O
as	O
Prolog	B-Language
,	O
Answer	B-Application
set	I-Application
programming	I-Application
,	O
SQL	B-Language
(	O
or	O
Datalog	B-Language
)	O
,	O
or	O
the	O
Planning	B-Application
Domain	I-Application
Definition	I-Application
Language	I-Application
,	O
for	O
example	O
.	O
</s>
<s>
Below	O
,	O
we	O
illustrate	O
the	O
components	O
of	O
a	O
GOAL	O
agent	O
program	O
using	O
Prolog	B-Language
.	O
</s>
<s>
The	O
GOAL	O
agent	O
code	O
used	O
to	O
illustrate	O
the	O
structure	O
of	O
a	O
GOAL	O
agent	O
is	O
an	O
agent	O
that	O
is	O
able	O
to	O
solve	O
Blocks	B-General_Concept
world	I-General_Concept
problems	O
.	O
</s>
<s>
The	O
beliefs	O
of	O
the	O
agent	O
represent	O
the	O
current	O
state	O
of	O
the	O
Blocks	B-General_Concept
world	I-General_Concept
whereas	O
the	O
goals	O
of	O
the	O
agent	O
represent	O
the	O
goal	O
state	O
.	O
</s>
<s>
The	O
knowledge	O
section	O
listed	O
next	O
contains	O
additional	O
conceptual	O
or	O
domain	O
knowledge	O
related	O
to	O
the	O
Blocks	B-General_Concept
world	I-General_Concept
domain	O
.	O
</s>
<s>
Actions	O
,	O
such	O
as	O
the	O
move	O
action	O
used	O
above	O
,	O
are	O
specified	O
using	O
a	O
STRIPS-style	O
specification	O
of	O
preconditions	O
and	O
postconditions	O
.	O
</s>
<s>
The	O
GOAL	B-Language
agent	I-Language
programming	I-Language
language	I-Language
is	O
related	O
to	O
but	O
different	O
from	O
other	O
agent	O
programming	O
languages	O
such	O
as	O
,	O
AgentSpeak	B-Language
,	O
2APL	B-Language
,	O
,	O
JACK	B-Language
Intelligent	I-Language
Agents	I-Language
,	O
,	O
and	O
,	O
for	O
example	O
,	O
.	O
</s>
<s>
The	O
distinguishing	O
feature	O
of	O
GOAL	O
is	O
the	O
concept	O
of	O
a	O
declarative	B-Language
goal	O
.	O
</s>
<s>
GOAL	O
provides	O
a	O
programming	O
framework	O
with	O
a	O
strong	O
focus	O
on	O
declarative	B-Language
programming	I-Language
and	O
the	O
reasoning	O
capabilities	O
required	O
by	O
cognitive	B-Protocol
agents	I-Protocol
.	O
</s>
