Re: [docbook-apps] tagged and accessible PDF document with DocBook

[Bob Stayton <bobs@sagehill.net>]

Hi Tony,
Thanks for chiming in.  I guess I cannot expect to get an XSL-FO 
standard for PDF tagging.  If we are going to implement it, we will need 
to use the facilities in each XSL-FO processor.  Given that, I want to 
make sure what is output is usable, that is, meets the needs and 
standards of the accessibility community.

I just ran across a webpage titled:

http://508compliantdocumentconversion.com/finally-u-s-access-board-updates-interpretation-of-section-508/

which says that WCAG 2.0 has been designated as the Reference Standard 
of section 508 of the Rehabilitation Act.

I get that WCAG 2.0 is a W3C standard, but I don't know much about it. 
Do you think I should spend time studying this as the correct reference 
for implementing standard and usable tags in DocBook XSL?

Bob Stayton
Sagehill Enterprises
bobs@sagehill.net

On 4/3/2017 11:52 AM, Tony Graham wrote:
> On 03/04/2017 18:07, Bob Stayton wrote:
> > Hi Holger,
> > No, you didn't miss anything.  The DocBook XSL stylesheets currently do
> > not provide support for tagged PDFs.
> >
> > That said, my short investigation shows that implementing such support
> > is nontrivial.  Keep in mind that the DocBook stylesheets don't actually
> > create a PDF.  The stylesheets generate a FO version of the document,
> > and then an XSL-FO processor converts that to a PDF.  So DocBook XSL has
> > to generate additional markup in the FO output that an XSL-FO processor
> > can convert to PDF tags.
> >
> > It looks like each of the XSL-FO processors commonly used with DocBook
> > (FOP, XEP, and Antenna House) have different extensions for implementing
> > the FO needed to generate the PDF accessibility tags.  For example:
> >
> > FOP has fox:alt-text
> > XEP has rx:pdf-structure-tag
> > AH expects axf:pdftag
>
> Not quite. If you produce either Tagged PDF or PDF/UA using AH Formatter
> from either XSL-FO or HTML/XML+CSS, then AH Formatter will default to
> generating a PDF Tag based on the type of the current element. For
> example, fo:root generates 'Document' and fo:table generates 'Table'.
> See https://www.antennahouse.com/product/ahf64/ahf-pdf.html#taggedpdf
>
> @axf:pdftag is for when you want to override a default mapping. See
> https://www.antennahouse.com/product/ahf64/ahf-ext.html#axf.pdftag. You
> can use @axf:pdftag to set a different standard PDF Tag for that element
> or you can provide your own non-standard Tag name, in which case AH
> Formatter will also generate the mapping from the non-standard name to
> the default PDF Tag for that element so that the requirement of the
> spec for Tagged PDF for having a mapping to a known Tag is met.
>
> > This situation is similar to when PDF bookmarks were first implemented.
> > Each XSL-FO processor had their own extensions to implement that
> > feature, and DocBook XSL had to support all three extensions.  When XSL
> > 1.1 standardized the markup for bookmarks, then all the XSL-FO
> > processors eventually implemented that standard and so did DocBook XSL.
> ...
> > I would be interested in adding PDF tagging to DocBook XSL.  It would
> > help if there were a clear spec for how to do so.  If I have to figure
> > it out for each of three XSL-FO processors, that's going to take some
> > time.
>
> There is no current W3C Working Group for XSL-FO. There is the Print and
> Page Layout Community Group (https://www.w3.org/community/ppl/), of
> which I am the Chair, but it takes more than just a venue to produce a
> spec with enough impetus to convince multiple vendors/teams to implement
> it.
>
> Regards,
>
>
> Tony Graham.