Log in / Register

Forum › Bugs

Accessibility in footnotes

ricardopressbooks
I'm using PDF profile PDF/UA-1 and I applied footnotes following: https://www.princexml.com/doc/11/footnotes/
I noticed footnotes call thrown an accessibility issue: 
Structure element is incorrectly nested: Lbl in Reference


I tried to use tag type property: https://www.princexml.com/doc/12/doc-refs/#prop-prince-pdf-tag-type
.footnote::footnote-call {
    prince-pdf-tag-type: Lbl;
  }

but looks like it doesn't work for pseudo elements.

Is there a way to change footnote call PDF tag?
wangp
Which tool produces the error message?

The tag structure Prince generates for a footnote is recommended in this guide:
https://www.pdfa.org/resource/tagged-pdf-best-practice-guide-syntax/
Reference
    Lbl
        [footnote call]
Note
    Lbl
        [footnote marker]
    [footnote body]


The Accessibility Checker tool in Acrobat complains about the Lbl under Reference, but it does have an option to turn off that check.
ricardopressbooks
I'm using https://pave-pdf.org/ for a11y checks.
Using Adobe I got a similar issue: 
Lbl and LBody - Failed  Lbl/LBody


I prefer keep the checker turned on.
According to https://www.w3.org/TR/WCAG20-TECHS/PDF21.htm:

The PDF specification defines list structure in section 14.8.4.3.3 (List Elements). The structure types for lists in PDF documents are:
L - the List tag, which contains one or more LI tags.
LI - the List Item tag. List item tags can contain Lbl and LBody tags.
Lbl - the list item label. Contains distinguishing information such as a item number or bullet character.
LBody - the list item body. Contains list item content, or in the case of a nested list, it may contain additional List tag trees.
Source: https://www.w3.org/TR/WCAG20-TECHS/PDF21.html

Looks like we need a LBody in the footnotes call.

Edited by ricardopressbooks

wangp
I have contacted the authors of PAVE for their opinion.

The WCAG advice relates to lists, not footnotes.

The name of the Acrobat accessibility checker option "Lbl and LBody must be children of LI" contradicts PDF32000-1:2008 Table 338, which states that Note and BibEntry structure elements may have Lbl as a child (so not only LI). The spec says very little about Reference elements, though, so whether Lbl as a child of Reference is allowed or disallowed is unclear. We may well drop the Lbl under Reference as it (likely) has no effect with current ATs.
ricardopressbooks
Thank you for your answers and interest in helping me.
I will stay tuned for changes at this point.

Best regards.
  1. Screenshot from 2020-08-21 10-53-14.png‎ 67.8 kB ‎
    Error in Adobe