Designing for “Raressential” Functions: Usage Patterns and UI Guidelines for Infrequent but Essential Tasks

As the number of functions offered by IT devices and services has grown with technological advances, designers have increasingly incorporated factors such as usage frequency and importance into the design of the user interface (UI). In this process, rarely used functions were pushed to the remote corners of the interface; some of these include infrequent but essential functions (“raressential” functions) that can significantly affect the user experience of a service. Despite their impact on user satisfaction, there have been few studies addressing the issues arising from the use of raressential functions. This study investigates usage patterns of representative raressential functions in order to propose design guidelines for UIs with such functions. Twenty-five participants were asked to sketch and perform the process for locating raressential functions in three different platforms. The protocol analysis and data visualization identified that (1) the corners of the mobile screen are strong visual attractors, (2) the overlap between semantic scopes of icons or names complicates the searching process in the PC environment, and (3) the lack of understanding of application software hierarchy seriously hinders orderly navigation in the TV platform. Participants also exhibited repetitive search patterns unique to each platform that delayed the completion of the task. Additional behavioral characteristics and relevant design guidelines are proposed for enhancing user experience of raressential functions.