I.1.4. Intelligent agents
I.1.4.1. Agents and their environment
By definition, an agent is something able to perceive its
environment with the help of the sensors and to act on this environment with
the help of the effectors. The figure I.1 illustrates the way in which the
agents interact with their environment:
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AGENT
Sensors
Effectors
Figure I.1. Interaction between the agent and its environment
I.1.4.1.1 Example:
A human agent has got eyes, ears and other sensory organs
(sensors), and the hands, the feet and other parts of the body to act
(effector).
The word perception is used in this context to indicate that
the agent can receive entries at any moment. The continuation of perceptions of
an agent reflects the complete history of what the agent received. In general,
an agent will take a decision in a given moment given according to the complete
continuation of perceptions until that moment. In mathematical terms we can say
that the behavior of the agent is given by the function of the agent which
projects a given perception on an action.
The function which describes the behavior of an agent can be
presented in the form of a table. In view of an agent, on which we wants to
test, we can build this table by taking into account all the sequences of
perceptions and by determining which action the agent realizes in response; the
table is an external characterization of the agent. Initially, the function of
the agent for an artificial agent is implemented in the program of the
agent.
I.1.4.2. the concept of rationality
A rational agent is the one who acts correctly. So, to act
correctly means to do something which is correct; it's what allows the agent to
obtain better results (to succeed). There is therefore the necessity of
determining the way of measuring the successthe means of measuring the
success.
1. Measurements of output
Measurements of output include the criteria which determine
the success in the behavior of the agent. When the agent is located in an
environment, it generates a sequence of actions in accordance with perceptions
which it receives. This continuation of actions is the one which makes that its
habitat passes by a succession of states. If the continuation is that wanted,
then the agent will have acted correctly.
But there is not a single adequate measurement for all the
agents. In general, it is better to conceive measurements of utility in
agreement with what we want in the environment, more than in accordance with
how we believe that the agent should behave.
2. Rationality
Rationality in a given moment depends on four factors:
o The measurement of performance which describes the criterion
of success;
o The knowledge of the environment accumulated by the agent;
o The actions which the agent can achieve;
o The continuation of perceptions of the agent until this
moment.
This leads us to the definition of the rational agent:
In each possible continuation of the perceptions, a rational
agent will have to undertake actions which maximize its measurement of output,
while being based on the evidences brought by the sequence of perceptions and
on knowledge that the agent stored.
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