The landscape of interactive systems is shifting toward dynamic, generative experiences that empower users to explore and construct knowledge in real time. Yet, timelines -- a fundamental tool for representing historical and conceptual development -- remain largely static, limiting user agency and curiosity. We introduce the concept of a generative timeline: an AI-powered timeline that adapts to users' evolving questions by expanding or contracting in response to input. We instantiate this concept through KnowledgeTrail, a system that enables users to co-construct timelines of historical events and knowledge formation processes. Two user studies showed that KnowledgeTrail fosters curiosity-driven exploration, serendipitous discovery, and the ability to trace complex relationships between ideas and events, while citation features supported verification yet revealed fragile trust shaped by perceptions of source credibility. We contribute a vision for generative timelines as a new class of exploratory interface, along with design insights for balancing serendipity and credibility.

翻译：交互系统的发展正朝着动态化、生成式的体验转变，旨在使用户能够实时探索和构建知识。然而，时间线——作为表征历史与概念发展的基本工具——在很大程度上仍是静态的，限制了用户的能动性与好奇心。我们提出了生成式时间线的概念：一种由人工智能驱动的、能够响应用户输入进行扩展或收缩，从而适应用户不断演变的问题的时间线。我们通过KnowledgeTrail系统具体实现了这一概念，该系统使用户能够共同构建关于历史事件和知识形成过程的时间线。两项用户研究表明，KnowledgeTrail促进了好奇心驱动的探索、偶发性发现以及追踪思想与事件之间复杂关系的能力，同时其引用功能支持了信息验证，但也揭示了由对来源可信度的感知所塑造的脆弱信任。我们提出了将生成式时间线作为一类新型探索性界面的愿景，并提供了平衡偶发发现与可信度的设计洞见。