Section 1 Introduction
Although mathematical literature forms the basis of many scientific and technical (STEM) subjects, they still pose a considerable hurdle for Visually impaired (VI) learners. While there has been emphasis on making formulas accessible [7][9] and communicating xy-graphs with techniques like sonification [3][5], other mathematical diagrams have received considerably less attention. Furthermore, there is even less attention on aiding independent authoring of diagrams that not only makes it easy for VI learners to generate their own material but also to inspect its correctness and communicate it to their sighted peers.
Systems like Equatio [13] or Desmos [2] offer graphic calculator facilities that allow for easy generation of interactive graphics, offering a range of accessibility tools such as formula voicing and sonification. However, many of the input elements are still mainly designed for sighted users and the emphasis is mainly on xy-graphs. More traditional mathematical authoring methods include the production of graphics within the context of LaTeX typesetting using powerful graphing packages such as Pstricks [8] or Tikz [12]. In particular, TikZ has become the prevalent tool for authoring diagrams in scientific literature, including advanced mathematics, computer science, and theoretical physics. While undeniably powerful, its use frequently requires several cycles of visually inspecting the output and making subsequent adjustments. Moreover, while text and formulas of LaTeX documents can be made directly web-accessible, using tools like pandoc [6] and MathJax [1], resulting graphics will still be inaccessible.
Our goal is to enable all authors to generate accessible mathematical diagrams easily by creating a high-level description of the mathematical components of the diagram using a provided language with a relatively small, but intuitive, vocabulary. And in particular we want to support VI authors by reducing the inspection cycles by offering a simpler, XML-based language that automates many routine tasks, such as drawing grids and placing labels, while still providing the flexibility to handle unusual situations. Resulting SVG graphics are made accessible with the diagcess library [11][4], which was initially designed for the generation of accessible chemical diagrams. The library allows readers to interactively engage with the created diagrams by exploring them step-wise and on different layers, enabling aural rendering and sonfication.
Our work is based in the context of PreTeXt, a tool that facilitates the creation of accessible scholarly documents. A PreTeXt author describes the structure of their document in XML while keeping the mathematical content in standard LaTeX. Thus, similar to LaTeX, documents are written without concern for their visual appearance while authoring, and PreTeXt will create an accessible version of the document in a variety of formats, such as HTML, PDF, ePub, or Braille. Our graphical authoring langugage is designed in a similar spirit and will eventually allow PreTeXt authors the ability to create accessible graphics directly in their documents. Some examples of diagrams that can be generated and made accessible with our technique are presented in Figure 1.1. We will use the top left-most as a running example.
