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Re: PDF Reading order question

for

From: Duff Johnson
Date: Aug 2, 2024 7:03PM

While I agree with the practical advice you've offered I want to offer a clarification here:

> On Aug 2, 2024, at 19:24, Philip Kiff < <EMAIL REMOVED> > wrote:

<snip>

> I don't think there is a standard or guideline that provides strict rules in such cases. Technically, I think the WCAG tends to favour the author's "semantic" intention, while PDF/UA tends to favour something they call "logical" order.

It’s certainly true that there are no “strict rules in such cases” because semantic intent varies with the situation, the author, the intended audience, and so on.

Both WCAG and PDF/UA target “semantic intention”. It’s simply that in PDF/UA, semantic intent is encoded by way of the order resulting from traversal of the tag-tree, known as “logical content order”.

> But I know some folks who remediate PDFs believe that the reading order should match the visual/physical order as closely as possible because I think they consider the placement on the page to be part of the significant semantic meaning.

I think the reason is that these remediators are trying to provide an acceptable experience for users whose software doesn’t understand tagged PDF.

> And they aren't wrong. So that doesn't help deciding. There are two competing orders.

</snip>

There are not “competing” orders in PDF. There are multiple orderings for various purposes. Reading order is intended to establish the visual appearance while logical content order establishes the semantic intent.

The fact that some software still (25 years after the introduction of tagged PDF) cannot use the tags and relies on the visual ordering of content is a different problem.

Duff.