Systematic approaches to an integrated design of human-machine interaction that promote the perspective that system users should no longer be add-ons to the engineering design but should be an integrated part of the functional design are emerging. This article discusses the design of reliable human-machine systems from this point of view and considers 3 issues. First, it is argued that efforts to remove causes of human error by incremental improvement of system design is ineffective due to adaptive compensation by operators. Instead, design should be based on an explicit identification of the behavior-shaping system constraints and the boundaries of acceptable operation. Second, different approaches to modeling adaptive human-machine systems are reviewed, followed by the discussion of a systematic framework to represent system constraints at several levels of abstraction. Finally, the implications for making constraints and boundaries visible through an ecological interface design are discussed and a typology of interface formats is suggested.