IDEF, initially abbreviation of ICAM Definition, renamed in 1999 as Integration DEFinition, refers to a family of modeling languages in the field of systems and software engineering. They cover a wide range of uses, from functional modeling to data, simulation, object-oriented analysis/design and knowledge acquisition. These "definition languages" were developed under funding from U.S. Air Force and although still most commonly used by them, as well as other military and  United States Department of Defense (DoD) agencies, are in the public domain.