Find the system reaction
Functional analysis: classify and characterize functions - draw up functional specifications

The notion of reaction draws on the principles of physics. An action leads to a reaction (the principle of air escaping from a balloon and propelling it across the room).

Your study of the system or product consists, in this stage, of highlighting the reaction of each of the actions you have identified and the reaction of the system or product with the elements of the external environment (EME).

More specifically, the system's reaction characterizes its ability to defend itself against external aggression and against itself.

By studying the elements of the external environment (EME), you find all the system's defense reactions. Express them in simplified form, in a table, distinguishing between a service function (SF) and a technical function (TF).

You bring out the notions :