tier

A tier is a level in the MVC programming pattern.
In a utility network, a tier is part of the architectural structure of a subnetworks that helps to define its properties and restrictions. For example, an electric distribution system can be subdivided into "subtransmission", "medium voltage", and "low voltage" tiers. Each utility network can contain up to 63 tiers defined in one or more domain networks. A tier can also define the topological organization (radial or mesh) of subnetworks that all share the same properties and adhere to the same restrictions. Trace can be performed within these tiers or across tiers using the tier's trace configuration; this configuration can support traversability, propagators, and function barriers.