Olli - Screen Reader Accessibility for Data Visualization

Olli is an open-source library for converting data visualizations into accessible text structures for screen reader users. Starting with an existing visualization specification created with a supported toolkit, Olli produces a keyboard-navigable tree view with descriptions at varying levels of detail. Users can explore these structures both to get an initial overview, and to dive into the data in more detail.

Using Olli

For a user tutorial, quickstart guide, and examples, see the Olli website.

Development instructions

• Fork and clone the mitvis/olli repository.
• In the olli directory, run npm install to install dependencies for all packages. We use npm workspaces to manage the two packages in this repo.
• In the core or adapters package directories, run npm run start to start the webpack bundler in development mode with file watching.
  • Note: olli must be built before olli-adapters the first time you run the build scripts.
  • Run npm run build to run webpack for production.
• To run scripts for both packages at the same time, run commands from the olli directory using the -ws flag, e.g. npm run build -ws.

Running the docsite locally

• The documentation site uses jekyll, and is served on github pages from the docs/ folder. See more about jekyll and gh-pages here.
• Run bundle exec jekyll serve in docs to serve the page at localhost:4000/olli.

Testing local changes on the docsite

• Run npm run start in the package(s) you are developing (i.e. in core and/or adapters). This starts webpack in watch mode with the dev config.
• Run bundle exec jekyll serve --livereload to serve the page at localhost:4000/olli with live reloading.
• Use the example gallery at localhost:4000/olli/examples to test changes locally.
  • When testing features, it's recommended to do initial testing on the multi-series line chart and scatterplot.
  • Validate across more examples before putting features into production.

Current Visualization Library Support

• Vega
• Vega-Lite
• ObservablePlot

Related Links

• Making data visualization more accessible for blind and low-vision individuals | MIT News
• Rich Screen Reader Experiences for Accessible Data Visualization | MIT Visualization Group

Reporting an Issue

If you encounter issues when using Olli, please file an issue on GitHub. Please include enough information to reproduce the issue. For example, if the issue is a bug with a chart that Olli should support with one of its adapters, please include the spec and dataset for the chart. For accessibility issues, please share what browser and screen reader you are using.

Contributions, Development, and Support

Interested in contributing to Olli? Please see our contribution and development guidelines, and our code of conduct.

Olli was originally created by Matt Blanco and the library is maintained by the MIT Visualization Group.