Subjunctive interfaces: Extending applications to support parallel setup, viewing and control of alternative scenarios

Many applications require exploration of alternative scenarios; most support it poorly. Subjunctive interfaces provide mechanisms for the parallel setup, viewing and control of scenarios, aiming to support users' thinking about and interaction with their choices. We illustrate how applications for information access, real-time simulation, and document design may be extended with these mechanisms. To investigate the usability of this form of extension, we compare a simple census browser against a version with a subjunctive interface. In the first of three studies, subjects reported higher satisfaction with the subjunctive interface, and relied less on interim marks on paper. No reduction in task completion time was found, however, mainly because some subjects encountered problems in setting up and controlling scenarios. At the end of a second, five-session study, users of a redesigned interface completed tasks 27% more quickly than with the simple interface. In the third study we examined how subjects reasoned about multiple-scenario setups in pursuing complex, open-ended data explorations. Our main observation was that subjects treated scenarios as information holders, using them creatively in various ways to facilitate task completion.