Analyzing some legacy EPUB files with mathematical formulas inserted as images, we realized an inconsistency between the ARIA and HTML-ARIA specifications.

The WAI-ARIA 1.2 specification provides an example of using role="math" on an <img> element to indicate that it represents a mathematical expression:

<img role="math" src="..." alt="x=⟮−b±√⟮b²−4ac⟯⟯÷2a">

However, according to the ARIA in HTML specification, the math role is not allowed on <img> elements. This discrepancy between the two specifications has led to confusion and inconsistent validation results.

The EPUBCheck validator reports an error when encountering role="math" on <img> elements, as it follows the ARIA in HTML specification (w3c/epubcheck#1562 (comment)).