2. For the present system, define its super-systems and sub-systems

Note that subsystems are potentially all the systems adjacent to your system that can play a role in its evolution. In the case of the watering can: the water, the user (man), the soil, the plants are potentially interactors that could have an influence (implied: if they evolve in turn) on the evolution of the watering can.

In some cases, the number of sub-systems can be considerable. In such cases, it is advisable to limit their number so that the study does not become time-consuming and obscure the essentials. If you have already carried out a study according to the law of completeness, the four parts (motor, transmission, work and control) will be a good starting point, reduced to four subsystem components.