Integrating status and event phenomena in formal specifications of interactive systems

In this paper we investigate the appropriateness of formal specification languages for the description of user interface phenomena. Specifically, we are concerned with the distinction between continuously available information, which we call status, and atomic, non-persistent information, which we call events. We propose a hybrid model and notation to address status and event phenomena symmetrically. We demonstrate the effectiveness of this model for designing and understanding mixed control interaction, an especially important topic in the design of multi-user systems.