YANG is a data modeling language for the NETCONF configuration management protocol. Together, NETCONF and YANG provide the tools that network administrators need to automate configuration tasks across heterogeneous devices in a software-defined network (SDN).
The YANG data modeling language provides descriptions of a network's nodes and their interactions. Each YANG module defines a hierarchy of data that can be used for NETCONF-based operations -- including configuration, state data, Remote Procedure Calls (RPCs) and notifications. Modules can import data from other external modules and include data from sub-modules.
YANG was developed by the IETF NETCONF Data Modeling Language Working Group (NETMOD) to be easily read by humans and as of this writing, Cisco, Juniper and Ericsson all support NETCONF and YANG. The YANG specification is published as RFC 6020 and YANG types as RFC 6021.
See also: management information base (MIB)