Agents

Agents definition

First of all, when talking about agents and multi-agent systems we should try to define what an agent is, however there is no one strict definition, a variety of different definitions exists. Some of them are quite simple, others are much more demanding. All strongly influenced by their background. A different definition will be used in area of artificial intelligence than in area of software engineering. A simple but clear and well understandable definition comes from S. Russel and P. Norvig:

“An agent is anything that can be viewed as perceiving its environment through sensors and acting upon that environment through effectors”.

Another, more precise definition that extends the one above is from P. Maess:

“Autonomous agents are computational systems that inhabit some complex dynamic environment, sense and act autonomously in this environment, and by doing so realize a set of goals or tasks for which they are deigned”

The second definition specifies the kind of agents we are interested in (it talks about computational agents which belongs to the area of engineering and has nothing to with natural agents from the field of biology such as human). It also says the agent are autonomous, which means they have a control over their actions and operate without direct interventions of other entities. Last difference from previous definition is that they are acting in order to achieve some specific goals.

An example of an agent according to a previous description is a thermostat. A simple autonomous device which is supposed to maintain temperature in a room. Maintaining the temperature is its goal. It contains a sensor to check what an actual temperature in the room is, a memory to remember what the desired temperature is and the values from the sensor and a decision-making function which compares the measured temperature with the desired one (making this decision is an action) and based on the result (using domain knowledge what to do when actual temperature is lower/higher that desired temperature) commands to turn the heating or the air conditioner on/off (commanding the heating is an effector).

Very similar specific definition is almost twenty years old and comes from G. Weiss (1999)

“An agent is a computer system that is situated in some environment, and that is capable of autonomous action in this environment in order to meet its design objectives”

From those three definitions we can see that an agent can be almost anything but in many cases, it is more specified and only a certain kind of agents is acceptable for a certain problem.