Echelon DM-21 Device Manager - Manual (Page 106)

G-4 Glossary
device. The Device Manager uses the program ID to identify the
devices it discovers. Devices with the same program ID must have
identical external interfaces.
See the Neuron C Programmer’s Guide, L ON M ARK 3.0 Application
Layer Guidelines, and Neuron Databook for more information about
the program ID.
Subsystem Devices, routers, and functional blocks are contained within
subsystems. With the LonMaker tool, each page in a Visio drawing
generally refers to a subsystem. Subsystems are useful for grouping
related devices. Subsystems may also be placed within other
subsystems, allowing the creation of a subsystem hierarchy for large
networks.
An LNS database can contain many subsystems. For example, a
network might consist of HVAC, lighting, and security subsystems.
These can be further divided into subsystems for each floor, and each
floor can be divided into subsystems for each room.