Include schema.org accessibility metadata to enable discovery no matter how the publication is distributed or consumed.
The schema.org CreativeWork class includes properties a set of properties used to identify the accessible qualities of a publication. This metadata can be expressed in HTML documents using RDFa or microdata attributes to identify the accessible qualities of the content (e.g., videos). It can also be included in the EPUB package document to provide an overall picture of the accessibility of the given rendition of the publication.
For more information about how to use each property, refer to their respective knowledge base pages: