Peripheral: A peripheral is a board that hosts physical I/O and usually does analog to digital conversion or digital to analog conversion. A peripheral cannot function on its own, it must be connected to a node. This is more narrow than the definition of a peripheral in embedded systems generally. Peripheral support is focused on complete boards, not individual components like an ADC. Although common abstractions for components specific to physical can be provided in this repository, general component abstractions / drivers should be made separately, such as in BFPOWER drivers.
Node: A node hosts peripherals. A node can have a commander but does not need one. A node can ignore or even override commands from the commander. In a complex system, nodes are intended to be kept simple, less likely to encounter an error than the commander, and in some cases should check for obvious problems in commands from the commander.
Commander: A commander hosts nodes. It is possible for a device to be both a node and a commander at the same time, although it may not be the best idea to make such a setup. There is no concept of nesting commanders built into Physical. If some kind of abstraction for a computer that commands multiple commanders, which command nodes, is necessary, it should be made for that specific application.