RIMMF stands for "RDA in Many Metadata Formats". It is a tool for creating and editing data compliant with RDA.
The latest full version is RIMMF3.
A beta version of RIMMF4 implements changes from the RDA Toolkit Restructure and Redesign (3R) Project.
RIMMF is used to create and augment r-balls, and is the main data entry tool for a Jane-athon.