Abstract
In this paper, we will propose a representational model of “interactive” artifacts which reflects interactions between human and artifacts base on the discussion of alethic, deontic and temporal aspects of the interaction. From these three types of modality, we will define three layers to represent the interactions. The base layer represents causal relations which are governed by physical laws or effects. The main layer represents state transitions by unrestricted operations. Some operations are restricted by teleological necessities which are derived from designers' intention. The top layer represent this type of restrictions by using what we call “task unit graph”. The tight interactions among the three layers explain interactions among designers, operator and environment via an artifact.
