Information Technology Reference
In-Depth Information
activation, the agent validates the action related to this context and executes it (or not).
It is a communication filter if the action is to add the message
m
that satisfies
f
m
in
the message box of the agent
a
. The agents can add and remove dynamically the filters.
Thus, they adapt their relation with the environment according to their needs.
In a crisis simulation, the agents have observable properties: their identifier, which
is unique, their location, their availability (
true/false
values) which specifies if an agent
rescues a victim, their skill (
position
/
monitoring
), their field of vision, and their internal
time. The messages have the following properties: their identifier that is unique, their
sender identifier, the sending time, the message type (
'request'/'accept'
), their location
which is the location of the sender when the message is put in the environment, the
identifier of the victim to rescue and the skill required by the sender in the case of com-
munication. The victims have four properties: their identifier, their location, their status
(
stretcher
/
vehicle
) and ”diagnosed”. The victims to be evacuated must be diagnosed;
this is expressed by the property
diagnosed
(
true/false
values).
In the simulation example, let
f
e
be a communication filter related to the following
context: an agent is interested by a message if it is available (
f
a
), if the request message
is close to the agent
a
and
a
has the requested skill (
f
m
) and if the victim has been
diagnosed (
f
c
). In this example,
f
c
contains one entity which is a victim identified
by the property
id
v
of the message. The request messages have information about the
victim location and the skill of the medical porter.
The processing of the context is traditionally done by the agents, but in EASI and
its extension EASS it is done by the environment. In this way, the computation can be
done with information that is shared by the agents (the entities descriptions) and with a
degree of mutualization. However, it implies the centralization of the computation and
the management of the information update. Now, we propose to evaluate the cost of this
centralization.
4
Theoretical Assessment
The theoretical assessment is the comparison between the processing by the environ-
ment of a communication filter for
n
a
agents and the processing by
n
a
agents of all the
messages. In order to take into account the context dynamics, this theoretical assess-
ment also studies the update process of the MAS. The theoretical assessment is based
on two criteria. The first, noted
Cost
T
, is the number of tests performed during the fil-
tering process and the second, noted
Cost
M
, is the number of resulting messages. The
objective is to identify in which cases it is better to mediate the communication through
the environment than to manage it in the agents.
Following the definition given in section 3, a filter
f
has tests related to one agent
description (
f
a
), one message description (
f
m
) and a subset of entities (
f
c
). To simplify
the explanation, we assume there is only one entity to match
f
c
and this entity cannot
be an agent. This last assumption implies that there is no additional cost for the update
process if the message processing is executed by the agents. The following generic filter
illustrates our assessment, it is shown in a classical “if” structure:
