System Definition

A system is:

• a collection of elements or components, endowed with a structure,
• which realises functions, (which transform matter, energy or information,)
• which evolves through time, (in an environment, according to a set of purposes).

(J.L. Lemoigne. La Théorie du Système Général, PUF, 1977

To be fully specified according to the above definition, a system must be described from the point of view of its structure, its evolution, and its functions. We can represent a system by its projection on three axes:

1. Static: structure, data, memory, states.
2. Dynamic: evolution, transitions, synchronisation, events.
3. Algorithmic: functions, transformations.

(Jöel André & Pierre-Marie Delpech. Objects in Europe. Summer 1994).

System comes from Greek: Syn Histemi. I put together.

A system is a set of interrelated things.

Aristotle told us that relation comes from interaction or function.

Interaction happens through interfaces.

Functions do have a "signature".