2.1. System overview

The notion of system comes from Greek form of the word "systema" which means:

- to place,

- to add,

- to bring together different elements in an organized form.

The system can be defined as a group of elements between which a set of relationships is established in order to achieve a goal. It can be said, therefore, that the structure of the system is given by both the number of elements that make up the system and the connections, respectively, the relations between them.

The system can be defined by:

• the set of its elements;
• the set of internal and external connections;
• inputs and outputs of the system;
• the purpose of the system;
• behaviour and system operating ability.

A system can be opened or closed, depending on the intensity of relationships it maintains with other systems that are outside. A system communicates with its environment through input or output variables.