Rational Software
In 1994, he joined Rational Software, where he worked with Ivar Jacobson and Grady Booch ("the Three Amigos") to develop Unified Modeling Language (UML). Later they merged their software development methologies, OMT, OOSE and Booch into the Rational Unified Process (RUP). In 2003 he moved to IBM, after its acquisition of Rational Software. He retired in 2006.