NDL (Network Definition Language) was a compiler on Burroughs large systems computers used to create a network definition file for a data communications controller (DCC) and object code for a data communications processor (DCP) that interfaced between a message control program (written in DCALGOL) such as (RJE), (MCSII) or (CANDE) and its line adaptors and terminal network.
References
Network Definition Language Wikipedia(Text) CC BY-SA