Accessibility Metadata with schema.org
All accessible EPUB files must include the required accessibility metadata and the required conformance reporting metadata created by schema.org.
Accessibility Metadata (Required):
- accessMode — a human sensory perceptual system or cognitive faculty necessary to process or perceive the content (e.g., textual, visual, auditory, tactile)
- accessModeSufficient — a set of one or more access modes sufficient to consume the content without significant loss of information. An EPUB Publication might have more than one set of sufficient access modes for its consumption depending on the types of content it includes (i.e., unlike accessMode, this property takes into account any affordances for content that is not broadly accessible, such as the inclusion of transcripts for audio content).
- accessibilityFeature — features and adaptations that contribute to the overall accessibility of the content (e.g., alternative text, extended descriptions, captions)
- accessibilityHazard — any potential hazards that the content presents (e.g., flashing, motion simulation, sound)
- accessibilitySummary — a human-readable summary of the overall accessibility, which includes a description of any known deficiencies (e.g., lack of extended descriptions, specific hazards)
Conformance Reporting:
- conformsTo (WCAG level)
- certifiedBy (who certified this as being compliant)
- certifierCredential
Accessibility Metadata with ONIX
ONIX (ONline Information EXchange) is a standard template that organizes electronic book information and is hosted in its own XML file. ONIX messages are formed by codelists that group together information with shared semantics and provide them with numerical values. Codelist examples for books include:
- List 5 -Product identifiers: ISBN-10, ISBN-13, LCCN, etc.
- List 17 -Contributor roles: author, illustrator, designer, editor, translator, etc.
- List 27 -Subject scheme identifiers: Dewey, BISAC, keywords, etc.
Codelist 196 contains EPUB accessibility details that provide information on an EPUB’s accessibility features. A full list of codes in codelist 196 is available here: https://ns.editeur.org/onix/en/196.
ONIX should be thought of as a supplement for schema.org accessibility and conformance reporting metadata. By using both, publishers can provide more robust accessibility metadata. Review additional ONIX resources.