This document reports on work done by the Institute for Defense Analyses (IDA) for the Office of the Program Manager, Information Sharing Environment (PM-ISE), Office of the Director of National Intelligence and Deputy Chief Information Officer (DCIO) for Command, Control, Communications, and Computers and Information Infrastructure Capabilities (C4&IIC), Department of Defense (DoD) Chief Information Officer (CIO). The objective of this project is to assess the current state of communications interoperability between DoD public safety and emergency management (PS/EM) entities and U.S. civilian PS/EM entities and how that is likely to change as the next generation of public safety information systems is implemented across the nation. This white paper is the analysis of gaps in the coverage of PS/EM communications data requirements by the National Information Exchange Model (NIEM), version 4.0.