Hasselt

Implementing multimodal interactions with event-driven languages results in a ‘callback soup', a source code littered with a multitude of flags that have to be maintained in a self-consistent manner and across different event handlers. Prototyping multimodal interactions adds to the complexity and error sensitivity, since the program code has to be refined iteratively as developers explore different possibilities and solutions. The authors present a declarative language for rapid prototyping multimodal interactions: Hasselt permits declaring composite events, sets of events that are logically related because of the interaction they support, that can be easily bound to dedicated event handlers for separate interactions. The authors' approach allows the description of multimodal interactions at a higher level of abstraction than event languages, which saves developers from dealing with the typical ‘callback soup' thereby resulting in a gain in programming efficiency and a reduction in errors when writing event handling code. They compared Hasselt with using a traditional programming language with strong support for events in a study with 12 participants each having a solid background in software development. When performing equivalent modifications to a multimodal interaction, the use of Hasselt leads to higher completion rates, lower completion times, and less code testing than when using a mainstream event-driven language.