KAGRA VIS Operations Manual - SDF
SDF (from Setpoint Definition File) is a tool that is part of the RCG (Realtime Code Generator) system that compiles Simulink models to run on the front-end computers. It allows monitoring of very large numbers of settings more efficiently (≈x100) than could be done by trying to read them with EPICS.
See LIGO-T1500115, JGW-G1809228.