RESNA 27th International Annual Confence

Technology & Disability: Research, Design, Practice & Policy

June 18 to June 22, 2004
Orlando, Florida

Accessibility Standards for Operating Systems

John Goldthwaite
Center for Assistive Technology and
Environmental Access , Georgia Tech


The Accessibility Working Group has been created by the Free Standards Group to develop accessibility standards that will enable universal access to computer systems, applications, and services. The Accessibility Working Group is developing a set of accessibility standards within the Linux Standard Base with the goals of improving overall accessibility of Open Source LSB platforms.


Accessible, operating system, Linux, Unix, Assistive Technology SPI


In September 2003, the Free Standards Group authorized the formation of an Accessibility Working Group to develop accessibility standards to enable universal access to computer systems, applications, and services. The Free Standards Group is an independent, nonprofit organization that promotes the use of free and open source software by developing and promoting standards. It is the driving force behind development of standards for the Linux operating system. The Free Standards Group has three major projects: Linux Standard Base (LSB), OpenI18N and the Accessibility Working Group. The Linux Standard Base is a set of behavioral protocols and tests that increase binary compatibility among Linux distributions and enable software applications to run on any certified Linux system. OpenI18N is a standard that creates a foundation for internationalization of compliant distributions and applications.

The Linux Standard Base (LSB) is developing a set of binary standards that promote compatibility among Linux systems (and other 'Unix-like" systems), and enable software applications to run on any version of Linux that conforms to LSB. The LSB Specification is a binary compatibility standard that specifies the binary environment in which an LSB compliant application executes. It ensures that a compliant application will run with out changes on all LSB compliant platforms for the same processor.

The Accessibility Working Group is developing a set of accessibility standards within the Linux Standard Base with the goals of improving overall accessibility of Open Source LSB platforms (e.g. Red Hat, Debian, and SuSE Linux). The project also will foster interoperability and binary compatibility for assistive technologies on these platforms so that assistive technology developers can be assured that their products will run on all platforms without modification and that compliant application software interoperates with their AT.

In addition to creating the specification, the group will develop test methods to determine if a LSB runtime platform conforms to the standard. This will allow a company to certify that its operating system is conforming to the standard. Third, the group will develop tests for application software so that they can be certified as conforming to the standard and can be assured of interoperating with assistive technology.


The Working Group has developed a plan in which the project's goals are accomplished over a five year period. The first year will focus on adoption of prior work in this area. Committees have been created to work adoption of the AT-SPI from the GNOME environment and AccessX from Xwindows. A third committee has been created to work on an Input/Output framework that would allow multiple programs to share resources such a sound card or Braille display.

In year two the working group will address accessible system set up, support for magnification and text to speech. The first project will devise a text mode for boot up so that the entire boot up and installation process can be accessible. Magnification support will create a service application program interface(API) that will provide services to the magnification software. It will remove device driver dependencies and isolate utilities from drivers so that magnification software works smoothly with various types of graphics hardware.

In year three and four, the working group will create Accessibility Standard for Administrators, an Installation Standard for Accessibility, and a Comprehensive Braille Standard. In year five the project will develop a Voice based I/O standard.



The Assistive Technology Service Provider Interface (AT-SPI) was developed for the GNOME2 desktop. The AT-SPI is being adopted by the KDE desktop developers. KDE and GNOME are the main graphical desktop environments for Linux.

AT-SPI is compatible with and supported by the GTK+2 and Java/Swing development toolkits and his been used in development of the Mozilla browser suite, and StarOffice/OpenOffice. TrollTech has announced that they will support AT-SPI in version 4 of the Qt toolkit (on which KDE is based).

AT-SPI enables assistive technology tools, e.g. screen readers, magnifiers, to query and interact with graphical user interface (GUI) controls. It facilitates access for individuals who cannot use the standard GUI. AT-SPI enables developers to build applications that are accessible. The AT-SPI enables developers and distributions to meet the accessibility requirements of many individual and corporate customers.

AT Device Shared IO

AT device shared I/O would make it possible for devices that are commonly used by persons with disabilities to operate smoothly with several client applications simultaneously.

In some circumstances it is necessary to support simultaneous access for different client applications. For example, allowing a software-based speech synthesizer to speak while a multi-media stream is playing rather than queueing the voice synthesizer's messages to play after the stream concludes. In addition, it may also be necessary to have messages queue or be suppressed until a particular window or console has focus.

The committee will support and coordinate the development of libraries that allow client applications to share these I/O devices. Shared access to accessibility related devices, such as Braille displays, reduces the cost of ownership and improves the user experience.

These libraries should offer a generic high-level abstraction of the underlying device to allow client applications, to use those libraries independent of the actual hardware in use. This simplifies the development of accessibility related software by sharing commonly used code such as low-level driver implementations in these libraries.

Two representative candidate libraries/APIs providing this service for braille devices, libbrl and brltty, are already available on the Linux platform.

Keyboard Accessibility

Persons unable to use a keyboard and mouse must use alternative devices. However, many users can be accommodated through software that causes a standard keyboard to behave differently. Many of these features and behaviors have long been available in the XKB specification available at

The Trace Center assisted in creating the XKB specification so it features the same accessibility features that can be found in Microsoft Windows and the Apple MacIntosh.

The committee will identify and adopt a subset of the XKB specification in order to provide standard keyboard features and behaviors required by persons with mobility impairments.

Additional information about the activities of the Accessibility Working Group can be found at the project website

Author Contact Information:

John Goldthwaite, MS
Center for Assistive Technology and Environmental Access
490 Tenth Street
Atlanta , GA 30332-0156 ,
Office Phone (404) 894-0563

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