[pdf-devel] Re: Logical document structure, tagged PDF and accessibility

[Jason White]

Leonard Rosenthol  <address@hidden> wrote:
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>
>Jason - do you mean support for creation of tagged PDF or
>consumption/viewing or something else?

To reply to this and associated questions in the thread, I have in mind both
creation of tagged PDF and its reading/consumption. As I understand this
project, the purpose is to write a PDF library that supports both consuming
and producing applications.

Tagged PDF and accessibility are strongly interrelated, since the preservation
of logical structure is invaluable to both braille and speech-based
renderings, and the specification indicates that it can also be used to assist
in visual presentation under certain circumstances which, I suspect, would
include screen enlargement.

As another example, the Orca screen reader, which relies on the ATK/AT-SPI
accessibility infrastructure, makes extensive use of logical document
structures in such applications as Firefox 3 to enable structural navigation
and reading of documents.

I am also aware of Adobe's proprietary implementation of both the reading and
writing of tagged PDF, and their support for accessibility APIs, but the
present concern is with free software implementations and with what happens on
the free desktop.

Naturally, I would appreciate details of any free/open implementations of
tagged PDF and associated features, as well as further discussion of what
might be possible in the context of the GNU PDF project. Obviously, a free (as
in freedom) accessible PDF reader would be desirable, as would more support
for tagged PDF in PDF writing applications. A less ambitious option, such as a
conversion tool that can extract the text and logical structure of a tagged
PDF document to an XML file, would also be highly useful. The pdftotext
utility in XPDF can't do this due to the underlying lack of support for tagged
PDF in XPDF itself. For untagged documents, pdftotext is nevertheless very
useful, and it's my tool of coice for reading PDF files under circumstances in
which I can't obtain the document in its original file format.