Current best practices recommend using textual descriptions to make data visualizations accessible to blind and low vision (BLV) screen reader users. While recent research has explored laying such descriptions out hierarchically to enable reading varying levels of detail, the textual descriptions remain fixed: their syntax and semantics are set by the visualization author or tool, and cannot be changed by a BLV user based on their preferences or task-specific needs. In this paper, we explore four characteristics of customizations for hierarchical textual descriptions of visualizations: presence, or what content is present in the description; verbosity, or the length and conciseness of the content; ordering, or the sequencing of content; and, duration, or how long a particular customization lasts. We instantiate these methods as extensions to Olli, an open source library that converts web-based visualizations into hierarchical textual structures, and evaluate our work through a mixed-methods study with 13 BLV participants. Users reported that customization is crucial to their agency and that being able to change the four characteristics helps them efficiently carry out their desired tasks on the data. However, differences in preferred defaults, prior experiences, and enthusiasm for customization indicate that there is no one-size-fits-all system even for customization itself: both accessible data visualizations and user interfaces for customizing them must be flexible enough to meet a variety of needs.

翻译：当前最佳实践建议使用文本描述使数据可视化对盲人和低视力（BLV）屏幕阅读器用户可访问。尽管近期研究探索了以层次化方式排列此类描述以支持阅读不同细节层次，但文本描述仍然是固定的：其句法和语义由可视化作者或工具设定，无法由BLV用户根据其偏好或特定任务需求进行更改。本文探讨了可视化层次化文本描述定制的四个特征：存在性（描述中包含的内容）、冗长度（内容的长度与简洁性）、顺序性（内容的排列顺序）以及持续性（特定定制的持续时间）。我们将这些方法实例化为Olli（一个将网络可视化转换为层次化文本结构的开源库）的扩展功能，并通过一项包含13名BLV参与者的混合方法研究评估了我们的工作。用户报告称定制对其能动性至关重要，且能够更改四个特征有助于他们高效完成数据相关任务。然而，在默认偏好、先前经验及定制热情方面的差异表明，即便是定制本身也不存在通用方案：无障碍数据可视化及其定制用户界面都必须具备足够的灵活性以满足多样化需求。