The final operational release of NIEM version 3.1 has been published and is now available. NIEM 3.1 is a minor release that incorporates user needs since NIEM 3.0 was launched in November 2013.
NIEM 3.1 is available here.
The NIEM model was designed to accommodate updates on a regular basis in order to adapt and evolve with user needs. TheNIEM release cycle allows us to make these model updates on a predictable and sustainable schedule.