Unsupported DPUB ARIA roles should be used on elements with implicit fallback roles
Rule Description
When a Digital Publishing Role that is not supported is conveyed via a role attribute value, semantic information can only be conveyed to screen reader users via native HTML elements that have similar semantics for fallback.
Why it Matters
When a Digital Publishing Role that is not supported is conveyed via a role attribute value, semantic information can only be conveyed to screen reader users via native HTML elements that have similar semantics for fallback.
Proposed or recommended specifications such as WAI-ARIA DPUB roles are subject to becoming obsolete or remaining preliminary prototypes when not supported.
When there is no fallback role specified, assistive technologies such as screen readers may not be able to convey missing semantic and interaction information intended by the author to users.
How to Fix the Problem
Ensure all unsupported DPUB roles are only used on elements with implicit fallback roles.
Supported ARIA DPUB roles are to be applied to Sectioning Content, Grouping Content, Heading Content, Phrasing Content, <aside> and <body> elements where required with appropriate associated epub:type structural semantics values.
For related information about DPUB roles, see W3 DPUB-ARIA 1.0 Roles.
The Algorithm (in simple terms)
Finds elements with one of the targeted DPUB roles that does not have an implicit fallback role.