EPUB Rules

In addition to the HTML rules, Ace implements EPUB-specific checks. The “impact” property indicates the severity of each violation (“minor”, “moderate”, “serious”, or “critical”), as per Deque axe’s definition described in their documentation ( https://github.com/daisy/axe-core/blob/v4.7.2_DAISY/doc/issue_impact.md ).

• Missing metadata (impact = “serious”): metadata-accessmode, metadata-accessibilityfeature, metadata-accessibilityhazard
• Missing metadata (impact = “moderate”): metadata-accessibilitysummary, metadata-accessModesufficient
• Incorrect metadata values (impact = “moderate”): metadata-accessibilityfeature-invalid, metadata-accessibilityhazard-invalid (mixed positive and negative terms (e.g. noFlashingHazard and flashing), unknown mixed with none or other vocabulary values, or usage of terms not defined by the specification)
• Incorrect metadata values (impact = “minor”): metadata-accessmode-invalid, metadata-accessmodesufficient-invalid (usage of terms not defined by the specification)
• Missing authored page list when metadata printPageNumbers/pageBreakMarkers is present (impact = “moderate”): metadata-accessibilityFeature-printPageNumbers-nopagelist
• Mismatched page breaks in SMIL and in HTML documents (impact = “serious”): epub-pagelist-mediaoverlays
• Authored page list references elements in HTML documents that are not page breaks or do not exist (impact = “serious”): epub-pagelist-broken
• Authored page list does not reference all elements that are page breaks in HTML documents (impact = serious): epub-pagelist-missing-pagebreak
• Mismatched authored table of contents and reading order of elements inside HTML documents (impact = “serious”): epub-toc-order
• Missing publication title metadata (impact = “serious”): epub-title
• Missing OPF lang attribute (impact = “serious”): epub-lang
• Missing dc:source publication metadata when reflowable EPUB has authored page list (impact = “serious”): epub-pagesource