When using search engines, people often issue multiple related queries to accomplish a complex search task. A simple query-task structure may not fully capture the complexity of query relations since people may divide a task into multiple subtasks. As a result, this paper applies a three-level hierarchical structure with query, goal and mission - a mission includes several goals, and a goal consists of multiple queries. Particularly, we focus on analyzing query-goal-mission structure for mobile web search because of its increasing popularity and lack of investigation in the literature. This study has three main contributions: (1) we study the query-goal-mission structure for mobile web search, which was not studied before. (2) We identify several differences between mobile and desktop search patterns in terms of goal/mission length, duration and interleaving. (3) We demonstrate that the query-goal-mission structure can be applied to design better user satisfaction metrics. Specifically, goal-based search success rate and mission-based abandonment rate are better aligned with users' long-term engagement than query and session based metrics.

As adaptive agents become more complex and take increasing autonomy in their user's lives, it becomes more important for users to trust and understand these agents. Little work has been done, however, to study what factors influence the level of trust users are willing to place in these agents. Without trust in the actions and results produced by these agents, their use and adoption as trusted assistants and partners will be severely limited. We present the results of a study among test users of CALO, one such complex adaptive agent system, to investigate themes surrounding trust and understandability. We identify and discuss eight major themes that significantly impact user trust in complex systems. We further provide guidelines for the design of trustable adaptive agents. Based on our analysis of these results, we conclude that the availability of explanation capabilities in these agents can address the majority of trust concerns identified by users.

We present an overview+detail document interface that draws on perceptual principles to help users work with documents. Central to our approach is the use of improved document overviews. Our approach also includes novel highlighting in the full representation of documents, as well as techniques to help users smoothly transition from the overview to the full representation of the document. We present a specific implementation of our design for Web browsing. We also present a qualitative user study that indicates that our perceptual design principles are effective and that users prefer our interface to traditional "find" and highlighting techniques. Our user study additionally reveals interesting tasks and strategies supported in our framework that have implications for overview+detail document interfaces in general