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

On 3 April 2017 at 21:12, Holger Bast <holgerbast@gmx.de> wrote:

> If there is no specification in xsl:fo how to apply the right structural information there will be no normative instance
> and all processors will handle these kind of information in their own manner. I

No, xsl-fo has no document wide 'structure'. If any, that should come
from your source XML and
be carried over to the fo, then PDF.

regards Dave

> Here are some of my resources, maybe they can help you:
> The following document gives a short overview how xml structural information can be applied to pdf. The document
> contains also a list of elements that should be tagged (see table 1)
> https://pdfs.semanticscholar.org/9a51/cd67046a81d4e02d6b4b35fa402bacc892f8.pdf
> PAC 2 - PDF Accessibility Checker (PAC 2)
> PAC is an easy to use tool to check if your pdf document is accessible. If not PAC will show you the problems in the
> structure as well as inside the document.
> http://www.access-for-all.ch/en/pdf-lab/pdf-accessibility-checker-pac.html
> And last but not least the pdf specification document. I didn't read the document yet. I try to get my hands on it in
> the next days.
> ISO 14289-1:2014 - Document management applications -- Electronic document file format enhancement for accessibility --
> Part 1: Use of ISO 32000-1 (PDF/UA-1)
> https://www.iso.org/standard/64599.html
> Holger
> Bob Stayton wrote:
>> 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.
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Dave Pawson
Docbook FAQ.

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