Metadata pub level
Discovery of Accessible eBooks
Here is a process we should support:
1) The publisher or their accessibility/distribution partners include in the EPUB 3.0.1 package document what accessibility features are in the EPUB based on Schema.org properties: http://www.w3.org/wiki/WebSchemas/Accessibility and http://www.idpf.org/accessibility/guidelines/content/meta/schema.org.php. Alternatively they can use ONIX accessibility fields for which these is a crosswalk to Schema.org: http://www.a11ymetadata.org/the-specification/metadata-crosswalk/.
2) The online retailer includes these accessibility properties (aka rich snippets) along with the other Schema.org properties they should also be using from an SEO rationale: http://www.moosylvania.com/blog/4-simple-website-optimizations-to-level-up-your-website/.
3) Consumers discover these accessible EPUBs via search engines. Though, Google's current search UI does not enable you to filter by a book's accessibility features, they are indexing these properties. You can see this by using their Custom Search Engine, which does allow you to narrow results by accessibility features in the search box:
4) When a consumer lands on the retailer's website based on the search above, the accessibility features are clearly presented. Bob Martinengo presented at a EDUPUB 1 a proposal for this: http://idpf.org/sites/default/files/file_attach/AMAC%20Presentation%20for%20EDUPUB.pdf and http://stepp.gatech.edu/dap.php.
The CSE above is configured to only search a narrow set of sites, but you can configure it to return results across the entire web. I hope the mainstream Google search expands their UI to includes these filters. They already have a filter for closed-captioning, which contextually appears when videos are in the search results.