Human-computer interaction (HCI) can effectively be understood as a continuous process
of cyclic interaction between the user and the environment. The action the user takes leads
to changes to the system or the environment. These are evaluated by the user, and then this
evaluation results in changes to goals, and then the user takes another action based on the
changes to goals. In order to effectively describe the continuous process of cyclic
interaction, a notation that a user interface designer could reason about the interactivity is
needed. This paper claims that a cyclic notation is able to account for the intimate
connection between goal, action and the environment, allowing a user interface designer to
make explicit what a process achieves, as well as what triggers that process. It is thus
possible for designers to build interactive versions of the designs so as to assess the
assumptions made or being made regarding the interaction between the user and the system
