Optimal UI Item Direction Definition (OUIID) in BiDi Interfaces: Method and Evaluation

The design process of BiDirectional (BiDi) interactive systems requires making decisions about the direction of the interface's UI items. The professional HCI literature traditionally assumes that each UI item has only one correct direction. We suggest that both directions can be appropriate for many UI items in BiDi interfaces, depending on contextual factors. This work introduces and evaluates the concept of optimal UI item direction (OUIID), a more nuanced, context-dependent perspective on the BiDi directionality problem. We evaluated the approach in an eye-tracking study with 30 UI items, by various measures of effectiveness, efficiency, and satisfaction. Using multi-objective optimization analysis across several measures, we demonstrate that OUIID varies depending on user expertise and prioritization of usability measures. The findings provide insights into design decisions in various setups.