Types of Assistive Technology | Types of Accessibility | Deciding How to Implement Accessibility

Technical Issues in Creating Accessible Software

Two sections below include more detailed technical information: see Access Issues for Selected Development Environments for background and resources on several common software development environments and The Guidelines for detailed guidelines on making math and science content accessible. Here we provide an introduction to technical issues in creating accessible software.

Types of Assistive Technology
Screen readers: software for blind users that finds information on the computer screen and communicates it to the user either with text-to-speech software or hardware or a refreshable braille display. Refreshable braille displays use pins that move up and down to spell out words in braille and are the fundamental means of access to computers for users who are deaf-blind. Screen readers are generally designed to get information using the standards of the operating system for which they are created; software that adheres to those standards will be most accessible, whereas software that ignores them may be impossible to access.

Screen magnifiers: software for low vision users that enlarges the screen image many times. Screen magnifiers may also permit the user to change the default colors of the display, for example, by using reverse video if that provides better contrast. Screen magnifiers track the cursor or the active region of the screen in order to automatically enlarge the portion of the screen the user needs to see. Therefore, software that uses a custom cursor may pose a challenge for accessibility since the wrong portion of the screen may be magnified.

Adaptive keyboards: a variety of keyboard options for users with physical disabilities who cannot use a standard keyboard. Keyboards may be smaller for users with little range of motion or larger for users without fine motor control; they may offer fewer choices for users who benefit from structured choices or provide a way to type with one hand for users who cannot use both hands. Additionally, software can be used to simulate a keyboard on the user's monitor. These on-screen keyboards allow those who cannot use other keyboards to type by pointing with a mouse (or an assistive technology that emulates a mouse). Software that uses the operating system's standard methods of reading input from the keyboard should not have difficulty being compatible with adaptive keyboards; reading keystrokes directly from the keyboard rather than through the operating system is likely to cause trouble.

Word prediction software: speeds up typing by presenting likely word choices as the user types. This software is often used with adaptive keyboards for users with physical disabilities. It is also beneficial to users who have difficulty with spelling or vocabulary.

Voice recognition software: allows the user to input data or control the computer by speaking. This is beneficial to users who have difficulty typing. Generally, software that allows full access through keyboard commands will be well suited for use with voice recognition.

Single switches: hardware for some users with physical disabilities who can only control the computer with one or two specific movements. Switches are used with software that scans through options on the screen allowing the user to trigger the switch when the option they wish to choose is highlighted. Single switches can be used in conjunction with on-screen keyboards and word prediction software. The scanning software can be used to create customized screen layouts for use with a variety of software. However, every clickable spot in the layout must be identified manually in advance.

Types of Accessibility
Software accessibility solutions fall into two categories: directly accessible and compatibly accessible. A "directly accessible" product is designed so that a person with a disability can operate all on-screen controls and access the product content without relying on the aid of an assistive technology. For example, to be accessible to users with low vision, directly accessible software offers features to enlarge all controls and on-screen text and is designed with high contrast colors or provides features that allow users to choose appropriate colors. To be accessible to blind users, a directly accessible product should have a keyboard interface with audio output. Such a keyboard interface will also provide access for many users with physical disabilities. Audio output should announce the presence and status of all on-screen controls and convey the atmosphere of the software. A built-in method of using a single key to scan through choices in the software will provide access for users who can only use a single switch as input. Teachers of students who are visually impaired report that their younger students get limited training with assistive technologies. For this reason, direct access is most crucial in products targeted for the elementary and middle school level.

Direct access has many benefits. The greatest is that the user is able to access educational software without needing special assistive hardware and software. This keeps costs down for schools and reduces the technical difficulties common when using assistive technology with multimedia software. It also allows the student with a disability to sit at any computer rather than always being directed to the adapted workstation. The more œexible classroom environment this creates benefits everyone. Finally, having the accessible interface designed by the people creating the software creates a better interface since the designers understand the educational intent and user interface model. An assistive technology must interpret the information given to it.

A "compatibly accessible" piece of software is designed with assistive technology in mind. This level of access assumes the user has a preferred assistive technology package installed and is relatively comfortable with it. Software that falls into this category is likely to be targeted at the high school level and beyond. Deaf-blind students are the exception to this target age. These students cannot use directly accessible technologies and rely on compatibly accessible materials from a young age. A compatibly accessible product is designed with "hooks" to facilitate ease of use with a screen reader, screen magnifier, or alternative input devices such as adapted keyboards or single switches. These hooks can be implemented by developers with tools such as Microsoft Active Accessibility (MSAA) and the Java Accessibility API from Sun Microsystems, (discussed in more detail in the section on development environments). Exposing the system cursor, using standard controls and fonts,and following the operating system's human interface guidelines can also help make a product compatibly accessible.

Compatible access has some advantages. It provides consistency of operation between applications since users already know how to navigate with their assistive technology or continually gain competency in doing so. In some cases it may be less expensive to develop software this way. Relying on the assistive technology package for text-to-speech capability in place of adding audio to a product can save on disk space for larger applications. Compatibly accessible products may be the only means of access for some users, i.e. deaf-blind braille users using screen readers to interact with computers. Building software compatible with assistive technologies should use a single set of programming techniques to create software that works well with screen readers, alternative input devices (switches, on-screen keyboards, voice recognition), and any other input or output device that is not part of a standard computer.

Deciding How to Implement Accessibility
This document provides techniques for creating both compatibly and directly accessible software. Deciding which techniques are best for an individual software product will require considering the likely nature of the software's use, as well as the ages of its users and their expected level of computer literacy. As discussed above, computer literacy varies greatly among students so it is best not to assume that students will have strong skills. For software intended for use at middle school or below, direct access generally provides the most reliable solution.

As with all questions about the usability of educational software, the goal is to increase students' time learning the material not time spent figuring out the software. So providing well-documented, easy-to-use features that configure software to eliminate the need for assistive technology is generally most desirable. If creating directly accessible software isn't possible, ensure that all students-not just the best prepared-can use the software. Avoid relying on advanced features that may not be common to all assistive technologies.

Certain compatibility techniques, particularly in software for high school and above, are broadly useful and, when part of the initial design, do not change the function of the software for any users. Some examples are text drawn to the screen as text and not as an image, menus standard to the operating system and keyboard equivalents for all mouse functions. These techniques can be less expensive than some direct access solutions, they are more general and impact a wide range of students, and they create a precedent for software developers to consistently use accessible programming techniques. For all of these reasons, use of compatibility techniques is encouraged in all software.