PreTeXt as Authoring Format for Accessible Alternative Media

We describe an approach for producing accessible mathematical content for blind learners, i.e., learners who primarily use screen readers and tactile materials to access information necessary for learning. Our main focus is on postsecondary education textbooks required for a course of study towards an undergraduate degree in mathematics. The basis for our approach is the PreTeXt authoring language, which combines a rigorous XML document structure with the strength of typesetting for formulas and graphics. This not only facilitates the production of formats such as PDF and EPUB but, more importantly, fully accessible HTML and tactile braille output from a single source file. The braille version of the text includes mathematical formulas in Nemeth braille as well as embossable tactile diagrams automatically generated from the source. Similarly, formulas in the HTML version are screen reader accessible, and the graphics can be explored interactively using screen reading and sonification. We applied our software to two large open-source textbooks on abstract algebra and calculus. The quality of the braille transcription was checked by a certified transcriber and the overall readability was checked by a blind mathematician. We have since experimented with the automatic translation of other mathematical textbooks to provide to blind student learners and volunteers.