DIRA: A model of the user interface

The user interface is a central concept in human-computer interaction, but peculiarly fuzzy. This affects discussions of the fundamentals of our discipline and the positioning of our work. We propose a model of the user interface that consists of four elements: Devices, Interaction Techniques, Representations, and Assemblies (DIRA). We explain their roles in the user interface and discuss some associated concerns about evaluation and design. We then show how to use the model to describe the elements of user interfaces (with examples that include a menu, a fisheye interface, and notifications) and to analyze the central characteristics of user interface paradigms (including tangible user interfaces and mixed reality). Finally, we discuss how describing user interfaces with the model can drive their design and evaluation.