Purpose: The timespan over which exploratory searching can occur, as well as the scope and volume of the search activities undertaken, can make it difficult for searchers to remember key details about their search activities. These difficulties are present both in the midst of searching as well as when resuming a search that spans multiple sessions. In this paper, we present a search interface designed to support cross-session exploratory search in a public digital library context. Methods: Search Timelines provides a visualization of current and past search activities via a dynamic timeline of the search activity (queries and saved resources). This timeline is presented at two levels of detail. An overview timeline is provided alongside the search results in a typical search engine results page design. A detailed timeline is provided in the workspace, where searchers can review the history of their search activities and their saved resources. A controlled laboratory study was conducted to compare this approach to a baseline interface modelled after a typical public digital library search/workspace interface. Results: Participants who used Search Timelines reported higher levels of user engagement, usability, and perceived knowledge gain, during an initial search session and when resuming the search after a 7-8 day interval. This came at the expense of the searchers taking more time to complete the search task, which we view as positive evidence of engagement in cross-session exploratory search processes. Conclusion: Search Timelines serves as an example of how lightweight visualization approaches can be used to enhance typical search interface designs to support exploratory search. The results highlight the value of providing persistent representations of past search activities within the search interface.

翻译：目的：探索性搜索的时间跨度、搜索活动的范围和规模，可能使搜索者难以记住其搜索活动的关键细节。这些困难既存在于搜索过程中，也存在于恢复跨多个会话的搜索时。本文提出一种搜索界面，旨在公共数字图书馆场景中支持跨会话探索性搜索。方法：搜索时间线通过动态时间线（展示查询与保存的资源）可视化当前及过去的搜索活动。该时间线提供两个详细层级：概览时间线以典型搜索引擎结果页设计形式与搜索结果并列显示；详细时间线则呈现在工作区中，供搜索者回顾搜索活动历史及已保存资源。我们通过受控实验室研究，将本方法与基于典型公共数字图书馆搜索/工作区界面建模的基线界面进行对比。结果：使用搜索时间线的参与者在初始搜索会话及间隔7-8天后恢复搜索时，报告了更高水平的用户参与度、可用性和感知知识增益。这以搜索者花费更多时间完成搜索任务为代价，我们将其视为参与跨会话探索性搜索过程的积极证据。结论：搜索时间线展示了如何利用轻量级可视化方法增强典型搜索界面设计以支持探索性搜索。研究结果突显了在搜索界面中提供历史搜索活动持久化表征的重要价值。