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Re: PDF/UA Matterhorn Protocols - how to use?


From: Christine Hogenkamp
Date: Jun 16, 2022 10:37AM

Thanks for the responses! Let me try to consolidate my replies:

@Lisa: Thanks for the link, we do sometimes use PAC3 (at client request)
and we have an ongoing doc for troubleshooting the errors we get; some are
easy to understand and others are more difficult to parse what needs to be
fixed and how. I have tried to find a comprehensive guide for PAC errors,
so far this website covers the most I've seen in one place:

Right now my research is more of a "future-proofing" for future projects
than "We actively need this for work right now" and I think I am slowly
wrapping my head around the idea that some of PDF/UA is not directly in the
hands of our designers, but more that we make sure we use programs that
will format the PDF correctly. Definitely some of the guidelines of PDF/UA
and the checkpoints of the Matterhorn Protocol seem to describe technical
aspects of PDF that are more software-oriented, for the apps that create
PDFs. Our designers just have to trust that InDesign is doing its job to
format the accessible tagged PDF if we do our part to format the file to
correctly create tags, logical reading order, alt text etc.

I would like for us to also improve our use of PAC 3 (or I think they just
released PAC 2021?) to get fewer errors, since that should mean our
formatting of the source design file has improved.

@Duff: Thank you for the helpful contextualizing of the Matterhorn
Protocol. It makes a lot of sense as a guide for software creation, there
are definitely some technical aspects that are deep in the "gears" of a PDF
that I think of as just the default state of a PDF file. We aren't looking
to reinvent the PDF wheel, just making sure we are using the correct
settings in InDesign (and correct fixes in Acrobat for things that can't be
done in Indesign) so that the tagged PDF is formatted to pass PDF/UA.

re: "It’s up to the user to understand that a list item’s bullet must be
contained in an <Lbl> tag, and not in the <LBody> tag (to take one common

We don't currently have a lot of info about correct formatting for PDF
tags, I'm a developer who works in HTML etc and I know PDF tags don't work
exactly like HTML tags do (with *some* overlap/similar structure) so I
would welcome any suggestions for resources/websites that can explain how
these common PDF tags should ideally be created by the app that creates the
PDFs. Even better if the info is Indesign specific :)

Currently we are at the mercy of how InDesign is programmed to export using
the tagged PDF option, for the overall arrangement of the tag tree and
which tags are used. I have noticed some discrepancy between how the tag
tree lists tags in the Structure panel of Indesign and the Tag panel of
Acrobat, the export process seems to create extra tags in a way we don't
have control over. Maybe that's ok? Maybe these defaults are the correct
tags a PDF needs in the overall document structure, such as the use of the
tags <Document> and <Art> etc? I have advised our designers to use the
native tools as much as possible to encourage the proper tags on export,
i.e. using the Insert Table dialogue, instead of creating a fake table with
the line tool or coloured boxes, etc.

re: "Matterhorn simply allows you to classify an error (In the above case,
01-006 "The structure type and attributes of a structure element are not
semantically appropriate for the structure element“) as it relates to

Oh that makes sense, to have a short form for each type of error. I think
what I will have to do is try to find a good place in our existing
accessible PDF workflow when we review the PDF to add a checklist of the
human-reviewable checkpoints and then the tester will have to use PAC 3 to
test the machine-testable ones. Maybe it's as simple as adding a
conditional step to our existing instructions, i.e. "If PDF needs to pass
PDF/UA, use table of checkpoints in doc 'Title of PDF/UA doc' for the items
that require human review, then use PAC 3"

And thank you for the link to "Tagged PDF Best Practice Guide: Syntax". It
has some great info, I have added it as a resource to our shared folder for
such docs. I have done so much reading lately my brain is swimming ha ha!

@Alan: Thank you for your perspective, do you have any recommendations for
tools that we could use? Currently we use the Acrobat Accessibility Checker
(just to catch basic errors) then we manually review the Tag panel for
correct logical reading order and tags used, and also test with NVDA to
ensure all content is focusable and read out, that the reading experience
seems good and the user can move around the doc in different ways.

*Christine Hogenkamp (She, Her)*
Front-end Developer
ContextCreative.com <http://contextcreative.com/>;

*20 years of purposeful creativity*
* ˟**˟*