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Guide to PAC errors?

Hello! Is there a place where the PAC error messages are explained? I am testing a PDF with PAC 2024 and got some "Inconsistent entry found" errors but the Question Mark icon just opens a web search, it doesn't provide an explanation.  It would also be useful if there was a way to know when an error is a false positive or can otherwise be ignored (i.e. not necessarily technically correct but also not known to have an effect on assistive technology reading the content). Thank you!

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Comments

5 comments

Date Votes
  • Official comment
    Thomas Schempp

    Hello, and thank you very much for your inquiry!

    As you know, PAC distinguishes between PDF/UA, WCAG, and Quality Checks. The help function (question mark) behaves differently in these three areas:

    • For WCAG, it links directly to the relevant page of the WCAG specification.

    • For Quality Checks, it opens the help content we created ourselves.

    • For PDF/UA, unfortunately, there is no comprehensive public website (as there is for WCAG). Since PAC is offered free of charge, it is currently not possible for us to create such extensive documentation ourselves. That’s why, for PDF/UA errors, PAC links to a Google search with the corresponding keywords.

    If the PDF/UA search does not deliver the results you need, we recommend the following approach:

    • Try refining the search manually or consulting an AI chatbot.

    • Use AvePDF, Adobe Acrobat Preflight, or veraPDF to validate your PDF document (veraPDF is very powerful, but unfortunately rather difficult to install).

  • Christine Hogenkamp

    Hi Thomas Schempp, thank you for the comment. I can appreciate not being able to offer an extensive resource for errors, but I think I am having a hard time parsing what the error might be referring to, due to the inexact phrasing of the error. Does "Inconsistent entry found" refer to some sort of error in the tag code itself, that it doesn't match how such a pdf/html tag should be formatted? As in an error in the code itself, like if I had placed a table tag within a header tag, which would be an inappropriate nesting semantically and programatically? 

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  • Patrick Foster

    Hello Christine Hogenkamp,

    Thank you very much for your clarification, I will answer on behalf of my colleague.

    As context, structure elements (or tags) can be found from content items as defined in ISO 32000-1 14.7.4.4. The error you are referring to can occur under two circumstances:

    1. The structure element (or tag) that references an annotation is not referenced by the annotation
    2. The structure element (of tag) that references a marked content item is not referenced by the marked content item
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  • Christine Hogenkamp

    Hi Patrick Foster thank you for the explanation I appreciate. For both items, for someone like me who is not a PDF programmer/specialist, could I ask you to expand on those circumstances a bit? I am trying to capture useful information about PDF remediation using PAC and it would be helpful if I could add an explanation that's more in "layperson terms" for non-technical people.

    I can parse that both items refer to a non-reciprocal relationships that needs to be reciprocal but it would be helpful if you could provide some real life document/tag examples to help me wrap my head around it :)

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  • Thomas Schempp

    Hello Christine, that’s a great follow-up question — thank you for asking it this way. You are exactly right: both situations refer to a relationship in the PDF structure that should be reciprocal but isn’t. Let me try to put it in more everyday terms with examples.

    1. Annotations (like links or comments)

      • In PDF/UA, when you tag an annotation (for example, a hyperlink in a paragraph), the tag and the annotation should point to each other.

      • Analogy: Think of it like a footnote in a book. The text says “see note 1,” and then at the bottom you have “note 1: …”. If either side is missing, the reference doesn’t make sense.

      • In an “inconsistent entry” case, the tag might say “this is linked to annotation A” but annotation A doesn’t acknowledge that link back (or the other way around).

    2. Marked content items (the actual pieces of text or images on the page)

      • Tags in the structure tree point to the marked content on the page, and that marked content should point back to the tag.

      • Analogy: Imagine you put a sticky note on a page that says “this paragraph belongs to section 2.” The sticky note points to the text. But the text itself should also be labeled as “part of section 2.” If one side forgets the other, PAC will say the entries are inconsistent.

      • A practical case could be a paragraph that is tagged as a heading in the structure tree, but the text on the page itself isn’t marked as belonging to that heading — so the relationship is “one-sided.”

    In short: PAC is alerting you that there is a mismatch between what the tag tree claims and what the actual page objects (annotations or text runs) acknowledge.

    You cannot fix this problem manually, but our product axesPDF provides a very simple solution: you can just click Rebuild Structural Parent Tree. This function resolves the inconsistencies with a single click.

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