Which language defines the data modeling structure used by NETCONF and RESTCONF?

YANG (Yet Another Next Generation) is the data modeling language used by NETCONF and RESTCONF. It defines the structure, syntax, and semantics of the configuration and state data, as well as the operations that can be performed on network devices. This allows for standardized, programmatic interaction with network devices. YAML, XML, and JSON are data serialization formats. While XML and JSON are commonly used to encode the data exchanged via NETCONF and RESTCONF (respectively), they do not define the data model itself. YANG defines the structure, and XML or JSON then represent instances of that structure. YAML is another serialization format but is not natively used by NETCONF or RESTCONF for data exchange.