Fig. 5.

Norman’s “seven stages of action” model, as applied to the interaction with a medication alerting system. Top: Loop a (on the left; “display/read” the alert) represents the core interaction. Loop b (“acknowledgement”) represents a second order interaction: not all alerting systems require alerts to be acknowledged. Usability design principles that could (if applied) improve the quality of the interaction are linked to the corresponding stage of the model, when possible