A declarative approach to event-handling in visual programming languages

The authors address the question of event-handling for declarative visual languages. In the approach presented, system-level, interactive, and user-defined events are fully-supported, while still maintaining the property of referential transparency. An approach to time termed temporal assignment provides a unifying mechanism for events to be defined as ordinary sequences of values, and conversely for ordinary sequences of values to be defined as events. This allows event-handling without additional concepts, and in particular provides a natural means for the user to define higher-level events of any kind