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Re: HTML5 Image Description Extension (longdesc) is Proposed Recommendation


From: Chagnon | PubCom
Date: Dec 6, 2014 8:55PM

Olaf wrote: "exactly what would you envision in for PDFs in this regard?"
I envision a defined feature, tag, attribute, or something else that would
allow a long detailed description to be available to assistive technologies
within the PDF, not outside it. It also needs to be easy to deploy for those
who create documents (see the end of my comments for more).

Olaf wrote: "Why not use a link?"
Because links outside the PDF (such as to specific URL webpages) break over
the lifetime of the PDF file. In large institutional environments
(government agencies, corporations, major publishers), it's difficult,
first, to define a specific URL while the document is being created (I.T.
generally doesn't like specifying this before the document is finalized),
and second, ensure that the link will still be working a year or more down
the road.

Plus, PDFs are often downloaded to individual computers and we can never
assume that the end user will have a live internet connection when reading
the document to visit a specified URL for the longdesc.

Links inside the PDF would have to link to pages that are added to the PDF
but are not in the printed version of the document. An example: a client's
360-page statistical document has approximately 100 statistical, complex,
graphical charts. The printed version of the document is OK and doesn't need
anything like longdesc. However the matching electronic PDF version would
now have to have an additional 30-50 pages added at the back of the book to
accommodate longdesc descriptions for those charts, sort of like a special
appendix of longdesc descriptions. This produces an electronic PDF version
that isn't identical to the printed hardcopy, and that gets my clients in a
tizzy; their agencies have interpreted the US federal law requiring
electronic versions of all printed documents as meaning that the electronic
version must match the printed version. So an electronic version with an
extra appendix doesn't meet their federal requirements.

Olaf wrote:
"The longdesc attribute as defined for HTML runs the risk of hiding the
longdesc-referenced content from certain groups of users. ... What I do know
for sure is that due to the reduced discoverability of longdesc it is
inferior to simply using a link."

Why is longdesc less discoverable or hidden from certain users?
Is that the fault of the attribute itself, the W3C definition of longdesc,
or the lack of programming by assistive technology manufacturers?

If I recall correctly, the H1 tag wasn't discoverable by screen readers way
back when. But over time, A.T. manufacturers have improved their software to
discover H1 and many more tags and conventions that are now our standards.
Thank goodness we didn't throw out heading tags back then just because
assistive technologies wouldn't deal with them!

What prevents longdesc from becoming a recommended
standard/procedure/technique that can be used by those who create documents,
as well as for A.T. manufacturers to develop functionality for their users?

What's needed:
I don't care whether it's longdesc or some other system of tag and/or
attribute, but we need a method where the people who create this type of
visually complex graphical data (e.g., charts, maps, flow charts, plans,
technical drawings, etc.) can easily write a detailed explanation of their

We need the author of the document to create this, not the accessibility
technician who follows him, nor the web team, nor the editors, nor the
graphic designers, nor anyone else in a typical publishing workflow who
completes the document after the author is done.

This task has to be done by the author. So right there, that leaves out
links - internal PDF links or external website URL links - because the
authors can't code them at their stage of a publication's workflow. This
type of document usually takes a year or longer to write and I.T. can't
determine where it will live on the website at that point.

So a feature/utility as easy to use as Alt-Text in MS Word would be ideal:
- Right-click and write the Alt-text for the graphic.
- Right-click again and write the long description for the graphic.

If it's attached to the graphic inside the document (such as an attribute on
the <figure> tag like Alt-Text), then it stays with the graphic as the
document is edited and reflowed, and it will carry through from MS Word into
the exported PDF. Or if the content is converted to HTML it will travel with
it. Or if the Word file is imported into InDesign for desktop publishing
layout, it can carry through into that layout and its exported PDF. And if
the document is stored in a content management system (CMS), that it travels
with that version, too. Or when the document must conform to established
publishing DTDs, schemas, and standards (such as PubMed's DTD for the NLM

The functionality has to begin at the author stage and then travel through
the half-dozen or more workflow stages of publishing, which is much greater
than just Internet distribution alone.

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