A practical boundary between monitoring, local control, supervisory coordination and building operation.
Control is more than a point on a screen
A useful BMS connects sensors, local sequences, equipment states and operating schedules. A point that is merely displayed is not automatically being controlled.
The right boundary depends on equipment safety, response speed and what must continue when a supervisory network is unavailable.
Start with the operating objective
Define the condition the building must maintain, then identify the equipment, measurements and authority needed to achieve it. This creates a system that can be commissioned and maintained.