Using your fingers to think: Interactive exploration of subjective constraints

There is a class of complex problems where solutions must satisfy multiple subjective criteria, while meeting specific quantifiable constraints. Route planning for leisurely travel is an example of a problem in this class, where constraints including total available time, transit times, and budget constraints determine whether a potential solution is acceptable to the prospective traveller. In this paper we present an interface that leverages, metaphorically, the elastic properties of a rubber band to allow playful interaction with relevant constraints. The resulting touch-based human computer interface enables the traveller to explore the solution space in the sense that constraints can be played with in order to find a route that meets the traveller's subjective preferences. Formal step-by-step evaluation with nine subjects confirms that leveraging the rubber band metaphor is useful in constraint satisfaction and that using the interface is intuitive since it leverages real-world experiences.