摘要：Hierarchies are ubiquitous on the web, for structuring online catalogs and indexing multi-dimensional attributed datasets. They are a natural metaphor for information seeking if their levelwise structure mirrors the user's conception of the underlying domain. In other cases, they can be frustrating, especially if multiple drill-downs are necessary to arrive at information of interest. To support a broad range of users, site designers often expose multiple faceted classifications or provide within-page pruning mechanisms. We present a new technique, called out-of-turn interaction, that increases the richness of user interaction at hierarchical sites, without enumerating all possible completion paths in the site design. Using out-of-turn interaction, the user has the option to circumvent any navigation order imposed by the site and flexibly supply partial input that is otherwise relevant to the task. We conducted a user study to determine if and how users employ out-of-turn interaction, through a user interface we built called Extempore, for information-finding tasks. Extempore accepts out-of-turn input through voice or text and we employed it in a US congressional website for this study. Think-aloud protocols and questionnaires were utilized to understand users' rationale for choosing out-of-turn interaction. The results indicate that users are adept at discerning when out-of-turn interaction is necessary in a particular task, and actively interleaved it with browsing. However, users found cascading information across information-finding subtasks challenging. By empowering the user to supply unsolicited information while browsing, out-of-turn interaction bridges any mental mismatch between the user and the site. Our study not only improves our understanding of out-of-turn interaction, but also suggests further opportunities to enrich browsing experiences for users.
