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PDF/UA question about <Figure> / <Caption> hierarchy (tagged pdf)


From: Rick Davies
Date: May 31, 2019 10:26AM

This has got my head in a spin: is it best practice for a figure or image
with a caption to have a tagged PDF structure wherein the <Caption> structure
element is a sub-element of the <Figure> structure element? Or should they
both be at the same level? (Leaving <Div> grouping aside for now.)

This nice document:

'Tagged PDF Best Practice Guide'

gets near to providing the answer, but then veers off (page 6). Presumably
because ISO 32000-2 itself does not seem to 100% clear on this. FWIW my reading
of ISO 32000-2 is that <Caption> *should* be a child of <Figure>. But I can't
find any confirmatory text or examples.

Checking the tagging in the PDF version of ISO 32000-2, it appears that neither
table titles nor figure captions are tagged as <Caption>, which I naively expected
should be the case. Instead they are tagged as <P>, at the same level either
preceding or following the table or figure. Is this by best practice design, or
might it be an inadvertency?

BTW, anyone know of specific, non-Adobe developer forums for discussing PDF/UA tagging?

TIA for any help or advice ...