No group is more likely to benefit from web-based education than people with disabilities.

Learning over the Web can minimize the impact of disabilities by eliminating transportation barriers. It can allow students to reveal their disabilities at their discretion. It can promote equality among learners, with and without disabilities, reducing potential discrimination. And it can make previously inaccessible classroom materials accessible.

In short, people who are blind, deaf, or who have mobility impairments can overcome numerous educational and vocational barriers if online educational materials are produced in a way that makes them accessible.

Techniques and technologies are already in place for assuring such accessibility. What is missing is public awareness of these standards and policies to guarantee that they are followed.

A powerful example of accessible design can be found in the new web-based multimedia physics curriculum called "Physics Interactive Video Tutor" (PIVoT)1 created by the Massachusetts Institute of Technology (MIT). PIVoT is designed to provide freshman students with a virtual learning environment that offers the immediacy, responsiveness, and dynamism of a traditional tutor.

As part of PIVoT's activities, the Corporation for Public Broadcasting/WGBH National Center for Accessible Media (NCAM)2 is collaborating with MIT on a three-year project funded by the National Science Foundation and the Mitsubishi Electric America Foundation. Launched in January 2000, this project is using PIVoT as a model to test, implement, document, and promote the development of multimedia access solutions that will make distance-learning accessible to blind, low-vision, deaf, and hard-of-hearing students.

To understand the PIVoT approach, it is important to first understand why so much web-based material is difficult for disabled students to access.

Web browsers present information through software known as a graphical user interface (GUI). Navigation through GUIs is difficult for blind and visually impaired people because image maps, buttons, menus, and other controls are often invisible or nameless when accessed by a blind user's assistive technology, such as a screen reader or refreshable Braille display.

Access to most graphical content (such as drawings, photos, or image maps) must be provided via technical instructions known as "alt-text tags." The PIVoT web site is becoming a model of accessible Web site design and is striving for adherence to the Web Content Accessibility Guidelines of the World Wide Web Consortium's Web (W3C) Accessibility Initiative3

PIVoT supports disabled users in the following ways-

ú First, it offers better design and layout. NCAM is working with PIVoT designers to improve the Web site's layout so that blind users can more easily navigate the site. For example, designers have improved text/background contrast to help visually impaired students use the site more effectively.

ú Second, it offers access to tables. Reading and manipulating tables is an important way of processing scientific information-but tables present a particular problem for blind users. Tables require that the user refer to both row and column headings in order to interpret the information in a single cell. The PIVoT Web site is being designed to permit blind users to explore a set of tabular data more efficiently through cues that help them understand these relationships.

ú Third, it offers access to math equations. Improving access to equations and graphs is crucial in making math and science accessible to blind and visually impaired students. A promising standard is the MathML specification from the W3C. A discussion is underway regarding appropriate MathML browsers in conjunction with the User Agents Working Group of the Web Accessibility Initiative. Once tools are available for authoring MathML, the PIVoT project intends to use them to prepare physics materials for the Web. This solution should enable blind students to read and manipulate equations with output in speech and Braille.

ú Fourth, it offers access to multimedia. The MIT development team has elected to use the W3C's Synchronized Multimedia Integration Language (SMIL) to assemble and present the course's multimedia lectures and help files. NCAM's caption-authoring tool, the Media Access Generator (MAGpie), is being used in the PIVoT project to add captions to multimedia, thus simplifying the process of making these clips accessible to deaf and hard-of-hearing students. MAGpie can also sequence audio descriptions into SMIL presentations, making them more accessible to blind or visually impaired students.

When implemented from the start, accessibility features such as alt-text tags, captions, audio descriptions, and proper layout add little if anything to the cost of a Web site. However, when implemented as add-ons, after the site has been launched, considerable costs related to labor and time may be incurred as the site is retrofitted to accommodate specific features.

It is important to consider that accessibility improvements benefit all users, not just those who are disabled. For example, Web users who are not sight-impaired may turn off their browser's automatic image-loading feature to make use of alt-text tags to identify and manipulate images. All users have the option of using captioned multimedia when viewing movie clips in a noisy environment, or where the use of sound is not appropriate. Caption (text) tracks are also useful as indices for searching through large collections of digital video files-the captions act as keywords.

Within three years, the PIVoT project aims to:

ú Enable science-focused high school and college students who are blind, visually-impaired, deaf, or hard-of-hearing to participate in an innovative and challenging web-based introductory physics curriculum

ú Provide developers, publishers, and distributors of distance-learning and educational multimedia with recommended practices and an applied demonstration of accessible design principles for network-delivered multimedia

ú Enable the MIT Center for Advanced Educational Services4 to institutionalize the technical capabilities developed through this project to develop a range of future educational products that are accessible to individuals with disabilities

Through the application of pragmatic and common sense design and development standards it is possible to provide the enormous benefits of accessible online learning equally to all students.

1. http://www.wgbh.org/wgbh/pages/ncam/webaccess/Pivot/PIVoToff.htm
2. http://www.wgbh.org/ncam
3. http://www.w3.org/WAI
4. http://caes.mit.edu/