The Network package also defines network levels, that is networks views used for various representations. The user is free to define networks and sub-networks as needed.<br/><br/>The enumerated terms (<i>Nano, Micro</i>, <i>Meso</i>, <i>Macro</i>) don't depend on the nature of the network. The same terminology may apply for instance to electric networks, but semantics are not defined here.<br/><br/>In RSM however, the semantics of this enumeration are completely defined for railway networks in the restricted sense (tracks and lines): see the notes in RSM 1.2 Network package, and further clarifications in the Track package. Complying with the network level semantics is essential for data interoperability: experience shows that the re-mapping of different topology breakdowns is a computation-intensive task.<br/>