Information Technology Reference
In-Depth Information
4
NBDI Architecture
The NBDI (Norm-Belief-Desire-Intention) architecture extends the BDI architecture to
help agents on reasoning about the system norms. Norm is considered as a primary con-
cept that influences the agent while reasoning about its beliefs, desires and intentions.
The extensions we have made are represented in the NBDI architecture by the following
components, as illustrated in Figure 4:
Belief+Norm Review Function
,
Norm Selection
Function
,
Norm Filter
and
Plans
base
1
(that stores the plans of the agent).
In a nutshell, the NBDI architecture (Figure 4) works as follows. The agent perceives
information about the world by using its sensors. The sensed information is the input of
the
Belief+Norm Review Function
, an extension of
Belief Review Function
[8] defined
in the BDI architecture that is responsible for reviewing the
Beliefs
base taking into
account the current perception and ones already stored in the base.
In this work, we consider that norms are also stored in the
Beliefs
base, so, besides
performing the original functionality of the
Belief Review Function
,the
Belief+Norm
Review Function
is also responsible for:
(i)
in case the current perception is a norm,
reviewing the sets of adopted norms by comparing the information loaded in the new
norm with the norms and beliefs already stored in the base; and
(ii)
updating the sets
of adopted and activated norms, considering that some may become active and others
inactive due to the incoming perceptions.
Next, the
Option Generation Function
updates the agent's desires, and also their
priorities. Such adaptation must consider both agent's current beliefs and intentions,
and must be opportunistic, i.e., it should recognize when environmental circumstances
change advantageously to offer the agent new ways of achieving intentions, or the
possibility of achieving intentions that were otherwise unachievable [8]. Note that this
function works exactly as the original function described in the BDI architecture. This
function does not consider the norms stored in the
Beliefs
base while updating the agent
desires because the agent must be able to generate new desires or adapt the existing ones
without the influence of the norms. Our architecture considers that the agent is an
au-
tonomous goal-oriented entity that fulfils the system norms if it decides to do so
.
After reviewing the beliefs, desires, activated and adopted norms, the
Norm Selection
Function
is executed in order to
(i)
evaluate the activated norms in order to select the
ones that the agent has the intention to fulfil; and
(ii)
identify and solve the conflicts
among these norms.
Next, the
Norm Filter
, an extension of
Filter
[8] defined in the BDI architecture,
selects the desires that will become intentions taking into account the norms the agent
wants to fulfil. The plans that will achieve the intentions are also selected by following
the norms the agent wants to fulfil.
Finally, the
Action Selection Function
is responsible for performing the actions spec-
ified by the intention. The next subsections detail the components added to the original
BDI architecture, the one that was extended and a set of algorithms that demonstrate
how such components can be implemented.
1
Plans are composed by actions and states that the agent has the desire to achieve.