To facilitate high quality interaction during the regular use of computing systems, it is essential that the user interface (UI) deliver content and components in an appropriate manner. Although extended reality (XR) is emerging as a new computing platform, we still have a limited understanding of how best to design and present interactive content to users in such immersive environments. Adaptive UIs offer a promising approach for optimal presentation in XR as the user's environment, tasks, capabilities, and preferences vary under changing context. In this position paper, we present a design framework for adapting various characteristics of content presented in XR. We frame these as five considerations that need to be taken into account for adaptive XR UIs: What?, How Much?, Where?, How?, and When?. With this framework, we review literature on UI design and adaptation to reflect on approaches that have been adopted or developed in the past towards identifying current gaps and challenges, and opportunities for applying such approaches in XR. Using our framework, future work could identify and develop novel computational approaches for achieving successful adaptive user interfaces in such immersive environments.

翻译：为了在常规使用计算系统时实现高质量交互，用户界面（UI）必须以恰当方式呈现内容和组件至关重要。尽管扩展现实（XR）正作为一种新兴计算平台兴起，但我们对于在这种沉浸式环境中如何最佳设计与呈现交互内容的理解仍十分有限。随着用户的环境、任务、能力与偏好在动态情境中变化，自适应UI为XR中的最优呈现提供了一种颇具前景的方法。在这篇立场论文中，我们提出了一个设计框架，用于适配XR中呈现内容的多种特性。我们将这些特性归纳为自适应XR UI需考虑的五个维度：内容（What？）、数量（How Much？）、位置（Where？）、呈现方式（How？）与时机（When？）。借助该框架，我们回顾了UI设计与适配领域的文献，反思了过去采用或开发的方法，以识别当前存在的空白与挑战，以及将这些方法应用于XR的机遇。未来的研究可基于我们的框架，识别并开发新颖的计算方法，以在此类沉浸式环境中成功实现自适应用户界面。