Stands for ICAM Definition Method or Integration Definition Method. IDEF is a modeling methodology developed by the U.S. Air Force to help programmers design complicated software systems. IDEF can be divided into five separate modeling methods: IDEF0 (Function Modeling), IDEF1X (Data Modeling), IDEF2 (Simulation Model Design), IDEF3 (Process Description Capture), and IDEF4 (Object-Oriented Design).