The Future of Accessible Charts

(originally published on the Benetech DIAGRAM Center website, as part of their Office of Special Education Programs (OSEP) grant report)

by Doug Schepers, Fizz Studio, on behalf of the Benetech DIAGRAM Center. 8-September-2020.

One part of our remit was to investigate the viability of the ChartML format proposed in 2012 by Ed Summers and Julianna Langston of the SAS Institute. ChartML was intended as a neutral XML source format for representing data visualizations, to be transformed into suitable formats for visual, tactile, or sonification display.

The technology landscape has shifted from the time of that proposal, particularly in Web technology. There has been a shift away from domain-specific XML formats toward markup attribute-based semantics decoration of HTML and SVG, such as author-defined Dataset attributes or the Accessible Rich Internet Applications (WAI-ARIA) attributes, enhanced by script-based interaction.

Scalable Vector Graphics (SVG) has emerged as the graphics format of choice for data visualizations on the Web, and its markup metadata capabilities make it suitable as the source for other non-visual representations, including haptics and sonification. The native capabilities of the Web have also increased, introducing APIs both for haptics (the Vibration API) and sonification (the Web Audio API).

SVG was also enhanced to be more accessible to screen readers, detailed in the W3C WAI-ARIA Graphics Module and Graphics Accessibility API Mappings specifications.

These increased capabilities, as well as pressure from regulation, have led to a recent proliferation of accessible data visualizations in several major software packages. There is rapid iteration in the commercial and open-source product side of accessibility for charts, with many different approaches. In the coming years, this may culminate in shared common practices, and even in a universal standard for interaction and the interpretation of data visualizations within a standards body like W3C.

In addition, there is activity among W3C’s participants that may lead to more detailed guidelines for data visualizations, as distinct from the generic “complex image” guidelines, within the W3C Web Content Accessibility Guidelines (WCAG), which serve as the basis for regulation and legislation such as the US Section 508 directive. This has the potential to become a virtual cycle, where innovation in the market leads to standardization, which leads to widespread legal requirements, which in turn rewards technical and user experience innovation, all benefiting not just people with disabilities, but all consumers of data visualizations.

The DIAGRAM Center has fostered this progress in accessible data visualizations in three ways: by convening leading accessible charting developers, projects, and companies in discussions toward standards; by fostering community collarboration and development in our code sprints; and by disseminating this information to educators, parents, publishers, and software professionals through our reports, code repositories, and other publications. One recent success story from our code sprints was the creation of a new open-source software project called SparkBraille, which enables the easy creation of interactive tactile line and bar charts through a common refreshable braille display, right from the Web, with no special hardware or software required; this project was started and completed from scratch in the 3 days of our 2020 code sprint, and the developers continued to refine it after the event.

It is clear that the nature of digital accessibility of charts lies in the future of Web technology, Web standards, and Web applications. While not all the details are yet obvious, the renewed emphasis on digital content being “born accessible” has shifted, and will continue to shift, the market for data visualizations.