A methodology, AUI (Adaptive User Interface), is presented in this paper for the design of user interfaces that can accommodate users of different skill levels. The conceptual user interface model, referred to as the dialogue schema in the AUI methodology, is derived by analyzing the control structure of task requirements from the real time system and formal language perspectives. The dialogue schema is used to generate three forms of dialogues: question/answer, menu/form, and formal language. Alternative software tools to facilitate the AUI methodology are also discussed.