There is practically no design advice on how to construct usable virtual reality systems, even though severe usability problems have been reported. This paper describes an interaction model for virtual environments developed from Norman's (1988) theory of action, as a first step in creating design guidance. The model consists of cycles of action for goal oriented, exploratory and reactive behaviour. User actions are linked to design properties required for successful interaction. The design

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... erties represent desirable affordances of the virtual environment and can be presented as He! design guidelines and in checklist questionnaires for evaluation.