Greetings:
I received the following article via the ICADD mailing list. I
thought that NFB-RD subscribers would be interested in the
article as it speaks directly to concerns about how blind people
can access documents over the WWW written using PDF.
Regards,
Curtis Chong
curtisc@winternet.com
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THE ACCESSIBILITY OF PDF AND ADOBE ACROBAT VIEWERS
FOR THE VISUALLY DISABLED
June 30, 1995
Liz McQuarrie
Adobe Systems Incorporated
Adobe's Portable Document Format, the native file format of the Adobe Acrobat
products, is a final form description language for documents that is not tied
to any operating system or application. PDF provides the document layout
richness of Adobe PostScript and allows publishers to retain the look and
feel of their publication. On the World Wide Web, PDF is becoming
increasingly popular for documents that need the layout richness that
HTML currently does not provide. Corporations are also using PDF to
disseminate electronic documents over corporate networks, via e-mail, or on
CD-ROM.
For the visually disabled, however, there are currently some accessibility
issues associated with PDF and the use of Adobe Acrobat viewers (Reader and
Exchange) for viewing PDF files. This document describes Adobe's plans for
making both the Adobe Acrobat viewing products and the PDF file format
accessible for the visually disabled.
Overview of Acrobat and PDF Accessibility Plans
Adobe has the following plans to make PDF and the Adobe Acrobat products
accessible to the visually disabled:
Offer an Accessibility Plug-in for Adobe Acrobat on Microsoft
Windows (available in late 1995). The plug-in will allow users to access
Acrobat for Windows through cooperation with Windows screen-reading
programs, as well as output formatted ASCII that is compatible with
alternative output devices, such as Braille printers.
Enhance the PDF format and Adobe Acrobat for Logical Document Structure
(available in 1996). Adobe currently has an active project under way to
add knowledge of a document's logical structure to the PDF file format and
to build solutions based on these extensions. For visually disabled
users, the PDF structure project will deliver several accessibility
solutions.
Adobe Acrobat Viewers and Microsoft Windows Screen
Readers
Screen-reader programs allow the visually disabled to interact with the
Windows interface by interpreting what is happening on the display and
outputting that information to speech synthesis or refreshable Braille output
devices. Although screen-reader programs for DOS have been around for many
years, screen-reader programs for Microsoft Windows that provide reasonable
performance and functionality have only been introduced in the last year
or so.
Limited Screen Model and PDF Documents
The delay in the availability of Windows screen readers is due to a number of
factors. First, it is quite an intellectual challenge to present what is
happening on the Windows display to a visually disabled person in a way that
allows the user to be productive. This is because with Windows (or any
other GUI-based operating system), there may be multiple applications open
simultaneously, each of which has a title bar, menus and several child
windows for their data. Each application also has many visual controls to
present: icons, scroll bars, and dialog boxes that include check boxes,
buttons and list boxes.
To keep track of what is happening on the screen, Windows screen readers build
what is referred to as an off-screen model in memory, and then allow the user
to navigate through the screen model. For example, from the screen reader,
the user can select a particular application window to interact with. Then
once an application is selected, the user can navigate and read text in the
window. Reading text usually involves using commands like "Next Line,"
which reads the next line down the page, and "Previous Word," which reads the
word immediately to the left of the current word.
The current screen models for Windows for handling the text that is in an
application-specific window are very similar to the models developed for DOS.
These models can typically only represent text in simple documents, where the
document contains a single column of text that flows left to right and top
to bottom on the page. They cannot properly represent documents with more
complex layout, such as a multi-column newspaper or documents with text
that is not horizontal, like a tax form that contains vertical labels.
When the screen-reader program encounters such complex layout in an
application, it will likely make mistakes. For example, in a multi-column
document, the screen reader would probably read the first line in the first
column, followed by the first line in the second column, running the columns
together as if they were on the same line. Because many PDF documents have
such rich layout , the use of Windows screen readers with Acrobat on these
documents will not produce useful output for the visually disabled person.
For the future, Adobe is participating in discussions with Microsoft and
Windows screen reader vendors regarding a new Application Programming
Interface to screen readers in Windows that hopefully will more fully
support complex documents.
Conflicts Between the Acrobat Viewers and the Screen
Readers
The second factor that has delayed development of capable Windows screen-
reader programs is that there are no easy operating system "hooks" (or entry
points) in the current operating system (Windows 3.1) for developers to use to
build the screen readers. (Note that Microsoft is currently adding such
hooks to Windows 95.) The net result of this oversight is that developers
of Windows screen readers have each independently invented techniques for
capturing screen state for alternative output devices in often incompatible
ways.
Additionally, the Windows version of the Adobe Acrobat viewer really pushes
the Windows environment technically in order to render visually beautiful
documents with fonts that are very close to the author's original fonts.
This fact often causes the Acrobat viewer products to be incompatible with
many of the screen readers. Screen readers are not able to read any text
in the Acrobat document windows, regardless of the layout.
The Adobe Acrobat Solution for Windows for the Visually
Disabled
To make PDF documents accessible to visually disabled users of Microsoft
Windows, Adobe is developing a special plug-in for Acrobat. (A "plug-in" is
a piece of software that works with the standard Acrobat product and enhances
its capability.) This plug-in is called the "Accessibility Plug-in".
The Accessibility Plug-in for Acrobat will present an alternative view of the
open document in a separate window. This view will contain the text in as
close to reading order as possible, including presenting multi-column
documents as a single column, and "straightening" all non-horizontal text.
This alternative view will use only those text attributes that screen readers
currently understand, such as bold and italic.
The Accessibility Plug-in will interact with the primary Acrobat document
display in such a way as to make interaction as seamless as possible and will
allow the use of all standard Acrobat features, such as access to annotations
and hypertext links. Additionally, the Accessibility Plug-in will allow
users to export from PDF to ICADD-compliant ASCII, as well as to formatted
ASCII. ICADD (International Committee for Accessible Document Design) has
proposed using a set of tags based on SGML (Standard Generalized Markup
Language) with documents to enable them to work with alternative output
devices, such as Braille printers.
A Beta version of the Accessibility Plug-in for Windows will be available in
early fall, and will be distributed free of charge through a number of
channels, including the World Wide Web. The Accessibility Plug-in will work
with both the Acrobat Reader product, which is free, as well as Acrobat
Exchange.
Adobe Acrobat and Other Platforms
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