W3C

Techniques for User Agent Accessibility Guidelines 1.0

W3C Working Draft 11-August-1999

This version:
http://www.w3.org/TR/1999/WAI-USERAGENT-TECHS-19990811
(plain text, postscript, pdf, gzip tar file of HTML, zip archive of HTML)
Previous version:
http://www.w3.org/TR/1999/WAI-USERAGENT-19990331/wai-useragent-tech
Latest public version:
http://www.w3.org/TR/WAI-USERAGENT-TECHS
Latest Working Group version:
http://www.w3.org/WAI/UA/WAI-USERAGENT-TECHS
Latest public version of "User Agent Accessibility Guidelines 1.0":
http://www.w3.org/TR/WAI-USERAGENT
Editors:
Jon Gunderson <jongund@uiuc.edu>
Ian Jacobs <ij@w3.org>

Abstract

This document provides techniques for implementing the checkpoints defined in "User Agent Accessibility Guidelines 1.0". These techniques address the accessibility of user interfaces, content rendering, program interfaces, and languages such as HTML, CSS and SMIL.

This document is part of a series of accessibility documents published by the Web Accessibility Initiative.

Status of this document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C.

This is a W3C Working Draft for review by W3C Members and other interested parties. It is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". This is work in progress and does not imply endorsement by, or the consensus of, either W3C or Members of the WAI User Agent (UA) Working Group.

While User Agent Accessibility Guidelines 1.0 strives to be a stable document (as a W3C Recommendation), the current document is expected to evolve as technologies change and content developers discover more effective techniques for designing accessible Web sites and pages.

This document was first published for UA Working Group review on 16 July 1999, then reviewed by the WAI Interest Group.

This document has been produced as part of the Web Accessibility Initiative and intends to improve user agent accessibility for all users. The goals of the User Agent Guidelines Working Group are discussed in the Working Group charter. A list of the current Working Group members is available.

A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR.

Please send comments about this document to the public mailing list: w3c-wai-ua@w3.org.

Table of Contents


1 Priorities

Each checkpoint in this document is assigned a priority that indicates its importance for users.

[Priority 1]
This checkpoint must be implemented by user agents as a native feature or through compatibility with assistive technology, otherwise one or more groups of users with disabilities will find it impossible to access information. Satisfying this checkpoint is a basic requirement for some individuals to be able to use the Web.
[Priority 2]
This checkpoint should be implemented by user agents as a native feature or through compatibility with assistive technology, otherwise one or more groups of users will find it difficult to access information. Satisfying this checkpoint will remove significant barriers to accessing Web documents.
[Priority 3]
This checkpoint may be implemented by user agents as a native feature or through compatibility with assistive technology, to make it easier for one or more groups of users to access information. Satisfying this checkpoint will improve access to the Web for some individuals.

The checkpoints in this document are numbered to match their numbering in User Agent Accessibility Guidelines 1.0.

2 How the Techniques are Organized

This document is organized as follows:

User Agent Accessibility
This section introduces some general techniques to promote accessibility in user agent functionality.
Interfaces and Conventions
This section addresses user agent support for standard programming interfaces, operating system conventions, and W3C specifications.
HTML Techniques
This section explains how to implement features of HTML (refer to [HTML40], [HTML32]).
CSS Techniques
This section explains how to implement features of CSS1 and CSS2 (refer to [CSS1], [CSS2]).
SMIL Techniques
This section explains how to implement features of SMIL (refer to [SMIL].

A checkpoint map has been provided for navigation of the techniques. For each checkpoint, the map includes its definition (as it appears in the "User Agent Accessibility Guidelines 1.0") and links to applicable techniques for the checkpoint. In addition, the beginning of each section of this document lists the checkpoints that are addressed in that section.

2.1 Examples and Deprecated Examples

This document contains a number of examples that illustrate accessible solutions in HTML, CSS, etc. but also deprecated examples that illustrate what content developers should not do. The deprecated examples are highlighted and readers should approach them with caution -- they are meant for illustrative purposes only.

3 User agent accessibility

3.1 Access to content

Checkpoints in this section: 7.1, 7.2.

3.1.1 Changes in content language

Checkpoints in this section: 7.3.

3.2 Device independence

Checkpoints in this section: 1.2, 1.1, 1.3, 1.4, 1.5, 1.6

3.3 User control of style

To ensure accessibility, users must have final control over certain renderings.

For text and color:

Checkpoints in this section: 6.1, 6.2, 6.3, 6.4, 6.5, and 6.6.

[Ed. These may be rendered in a variety of ways. How do we specify rendering?]

For images, applets, and animations:

Checkpoints in this section: 5.2 and 6.7.

For user agents rendering audio:

Checkpoints in this section: 6.11, 6.13, 6.12, 7.9, and 7.6.

For user agents rendering video:

Checkpoints in this section: 6.8, 6.10, and 7.8.

For user agents rendering speech:

Checkpoints in this section: 6.15 and 6.14.

User interface:

Checkpoints in this section: 6.16.

3.3.1 Feature control

Checkpoints in this section: 5.1, 5.3, 5.4, 5.10, 5.9, and 5.5.

[Ed. Add note here that while useful to turn off support, say for all images, it's also useful to be able to view one particular image.]

User agents may:

For example, user agents may recognize the HTML construct target="_blank" and spawn the window according to the user's preference.

Checkpoints in this section: 5.14.

Period page refresh can be achieved with the following markup in HTML:

<META http-equiv="refresh" content="60">

The user agent should allow the user to disable this type of page refresh.

Checkpoints in this section: 5.13.

Although no HTML specification defines this behavior formally, some user agents support the use of the META element to refresh the current page after a specified number of seconds, with the option of replacing it by a different URI. Instead of this markup, authors should use server-side redirects (with HTTP).

User agents can provide a link to another page rather than changing the page automatically.

3.4 Selection and focus

3.4.1 Highlighting selection and focus

Checkpoints in this section: 9.2 and 9.3.

3.4.2 Tracking selection and focus

Checkpoints in this section: 9.5, 9.6, and 8.2.

3.5 Navigation and searching

Checkpoints in this section: 8.7

3.5.1 Navigation of active elements

Checkpoints in this section: 8.4.

Sequential navigation includes all active elements. User agents might provide other navigation mechanisms limited to a particular type of element. For example "Find the next table" or "Find the previous form". The following checkpoints suggest some types of navigation.

Direct navigation:

Excessive use of serial navigation can reduce the usability of software for both disabled and non-disabled users. As a developer, you need to determine the point at which tabbing gets in the way and provide a keyboard alternative. This is done through the use of keyboard Mnemonics and Accelerators.

3.5.2 Navigation of document structure

Checkpoints in this section: 8.6

3.5.3 Table navigation

Checkpoints in this section: 8.3

Users of non-visual rendering technologies and users with learning disabilities, when browsing a page, should be able to quickly determine the nature of a table located on a page. The able-bodied user is able to visually examine the table and extract a sense of the table contents with a quick scan of the cells. A non-visual user, or a user with difficulty translating printed material is not able to do this. Providing table summary information, when first moving the point-of-regard to a table allows the nature of a table to be easily determined.

An auditory rendering agent, when the point-of-regard moves to a table, might say, "Table: Tax tables for 1998," thus identifying the nature of the table. The user could then use keyboard commands to move the point of regard to the next logical block of information, or use a different command to "burrow" into the table.

The "burrow" command should have an opposite "pop" command, which would move the point of regard from an individual cell to the table as a whole, so that the user can leave a table from any cell within it, rather than navigating to the end.

If the user "pops" up to look over the summary information, it should be possible to "burrow" back to the same cell.

When navigating a table that contains another table, this strategy can avoid confusion. For example, if each row of a table contained five cells, but the second row contained a 4x4 table in the third cell, a user could be disoriented when the row did not end as expected. However, when the point of regard moved to the third cell of the table, a compliant browser would report that this was a table, and describe its contents. The user would have the option of navigating to the forth cell of the parent table, or burrowing into the table within this cell.

When rendering tabular information, the fact that it is tabular information should be apparent. For a visual user agent, such information is commonly made obvious by the border attribute. However, for a non-visual agent, such information must also be made appreciable.

As the user agent shifts the point of regard to a table, it should first provide information about the entire table. This information might be the Caption, Title, or Summary information of the table. Access to this information would allow the user to determine whether or not to examine the contents of the table, or to move the point of regard to the next block of content.

In many data tables, the meaning of the contents of a cell are related to the contents of adjacent cells. For example, in a table of sales figures, the sales for the current quarter might be best understood in relation to the sales for the previous quarter, located in the adjacent cell.

In order to provide access to contextual information for individuals using non-visual browsers, or for individuals with certain types of learning disabilities, it is necessary for the user agent to allow the point of regard to be moved from cell to cell, both right/left and up/down via keyboard commands.

The most direct method of performing such navigation would be via the cursor keys, though other navigation strategies might be used.

Users of visual browsers can easily locate cells within a table that are at the intersection of a row and column of interest. To provide equivalent access to users of non-visual browsers, equivalent means of navigation should be provided. The search function of a browser will allow the user to locate key terms within a table, but will not allow the user to find cells that are at the intersection of rows and columns of interest.

Techniques:

The header information visible in a TH cell may be abbreviated, in which case it should be user preference to see the "abbr" value if any or the full contents.

Axis information may also help the user search into confined portions of the table.

Column groups and row groups are other confining partitions of a table in which a search may be limited.

3.5.4 Searching

Checkpoints in this section: 8.5.

3.5.5 View navigation

Checkpoints in this section: 8.1, 9.8.

3.6 Context and orientation

3.6.1 Document status information

Checkpoints in this section: 9.14, 10.4, 10.3.

3.6.2 Document content

Checkpoints in this section: 9.9, 9.11, 9.10, 9.12, 9.4, 9.13.

3.6.3 Links

Checkpoints in this section: 9.18, 9.17, 9.15, 9.16, 9.10, 9.16

3.6.4 Tables

Checkpoints in this section: 9.19, 9.20.

3.6.5 Table cells

Checkpoints in this section: 9.22, 9.21, and 9.23.

3.6.6 Form controls

Checkpoints in this section: 9.24, 10.5.

[Ed. Talk about "for" attribute for LABEL]

3.6.7 Frames

Checkpoints in this section: 9.7.

3.6.8 Scripts

Checkpoints in this section: 10.1, 10.2.

3.7 Keyboard access

Checkpoints in this section: 2.1.

3.7.1 Tabbing order

3.7.2 Keyboard shortcuts

Checkpoints in this section: 2.2, 2.3, 2.6.

3.7.3 Software consistency

Checkpoints in this section: 9.25

3.8 Configuration

3.8.1 User profiles

Checkpoints in this section: 4.1

A configuration profile allows users to save their user agent settings and re-apply them easily, which is particularly valuable in an environment where several people may use the same machine.

The user should be able to easily transfer their profiles between installations of the same user agent. One way to facilitate this is to follow operating system conventions for profiles where applicable.

Users should be able to switch rapidly between profiles (or the default settings). This is helpful when:

User agents may apply a profile when the user logs in. They may also allow users to apply settings interactively, for example by allowing them to choose from a list of named profiles in a menu.

Sample profiles (based on common usage scenarios) can assist users in the initial set up of the user agent. These profiles can serve as models and may be copied and fine-tuned to mean an individual's particular needs.

3.8.2 Keyboard configuration

Checkpoints in this section: 2.4, 2.8, 2.7, and 2.5

[Ed. Discuss keyboard access here. How access is specified in HTML: "accesskey".]

[Ed. New section. Users must be allowed to control keyboard configuration based on specific needs. For poor motor control, keys far apart. For poor mobility, keys close together. General principle: fewest keystrokes, short distance to move.]

3.8.3 User interface

Checkpoints in this section: 4.2.

3.9 Documentation

Checkpoints in this section: 3.2.

Universal design means that access to features that help accessibility should be integrated into normal menus. User agents should avoid regrouping access to accessibility features into specialized menus. Documentation includes anything that explains how to install, get help for, use, or configure the product. Users must have access to installation information, either in electronic form (diskette, over the Web), by fax, or by telephone.

3.9.1 Where to document accessibility

Checkpoints in this section: 3.3.

Include references to accessibility features in these parts of the documentation:

  1. Indexes. Include terms related to product accessibility in the documentation index (e.g., "accessibility", "disability" or "disabilities").
  2. Tables of Contents Include terms related to product accessibility in the documentation table of contents (e.g., features that promote accessibility)
  3. Include instructions on how to modify all user configurable defaults and preferences (e.g, images, video, style sheets, and scripts) as specified by the documentation.
  4. Include a list of all keyboard shortcuts in the accessibility section of the documentation.

3.9.2 Accessible documentation

Checkpoints in this section: 3.1.

Documentation created in HTML should follow the Web Content Accessibility Guidelines.

Electronic documentation created in open standard formats such as HTML and ASCII can often be accessed in the user's choice of application such as a word processor or browser. Accessing documentation in familiar applications is particularly important to users with disabilities who must learn the functionalities of their tools, be able to configure them for their needs, and to be compatible with assistive technology. Electronic documentation should not be provided in proprietary formats.

Users with print impairments may need or desire documentation in alternative formats such as Braille, large print, or audio tape. User agent manufacturers may provide user manuals in alternative formats. Documents in alternative format documents can be created by agencies such as Recording for the Blind and Dyslexic and the National Braille Press.

User instructions should be created in an input device-independent manner. Provide instructions for using or configuring the user agent in a manner that can be understood by a user of any input device including a mouse or keyboard. For example, "Click on the Home button on the toolbar or select "Home" from the Go menu to return to the Home page. "

4 Interfaces and conventions

4.1 System conventions

Checkpoints in this section: 12.6

Develop the UA User Interface (UI) with standard interface components per the target platform(s). Most major operating system platforms provide a series of design and usability guidelines, these should be followed when possible (see platforms below).

These checklists, style guides, and human interface guidelines provide very valuable information for developing applications (e.g., UAs) for any platform/operating system/GUI. If your custom interface cannot provide information or operation as defined above, then you may need to design your UA using any additional options provided by that platform.

For instance, software should use the standard interface for keyboard events rather than working around it.

Evaluate your standard interface components on the target platform against any built in operating system accessibility functions (see Appendix 8) and be sure your UA operates properly with all these functions.

For example, take caution with the following:

4.1.1 Some guidelines for specific platforms

4.1.2 General guidelines for producing accessible software

4.2 Testing UA operation with platform standards

Ensure your UA can be operated using the standard interfaces on the target platform(s). Some example tests include:

4.3 Accessibility interfaces

Checkpoints in this section: 12.1, 12.2, 12.3, 12.5.

The operating system application programming interfaces (APIs) that support accessibility are designed to provide a bridge between the standard user interface supported by the operating system and alternative user interfaces developed by third-party assistive technology vendors to provide access to persons with disabilities. Applications supporting these APIs are therefore generally more compatible with third-party assistive technology.

The User Agent Accessibility Guidelines Working Group strongly recommends using and supporting APIs that improve accessibility and compatibility with third-party assistive technology. Third-party assistive technology can use the accessibility information provided by the APIs to provide an alternative user interface for various disabilities.

The following is an informative list of currently public APIs that support accessibility:

Many operating systems have built-in accessibility features for improving the usability of the standard operating system by persons with disabilities. When designing software that runs above an underlying operating system, developers should ensure that the application:

  1. Makes use of operating system level features. See the appendix of accessibility features for some common operating systems.
  2. Inherits operating system settings related to accessibility. Pertinent settings include font and color information as well as other pieces of information discussed in this document.

Write output to and take input from standard system APIs rather than direct from hardware controls where possible. This will enable the I/O to be redirected from or to assistive technology devices - for example, screen readers and braille devices often redirect output (or copy it) to a serial port, while many devices provide character input, or mimic mouse functionality. The use of generic APIs makes this feasible in a way which allows for interoperability of the assistive technology with a range of applications.

4.4 The document object model

Checkpoints in this section: 12.4.

Use DOM Level 1 [DOM1] for access to HTML and XML document information. However, as the DOM specification indicates:

The DOM Level 1 does not include mechanisms to access and modify style specified through CSS 1. Furthermore, it does not define an event model for HTML documents. This functionality is planned to be specified in a future Level of this specification.

It is important for user agents to provide access to style and scripting information in a document, so the following techniques should be used to achieve this.

Use standard rather than custom controls when designing user agents. Third-party assistive technology developers are more likely able to access standard controls than custom controls. If you must use custom controls, review them for accessibility and compatibility with third-party assistive technology.

4.5 Information for assistive technologies

[Ed. To be completed.]

5 Support for HTML accessibility

[Ed. Link to W3C Note on HTML Accessibility Features instead of this section]

Checkpoints in this section: 11.2, 11.1

Following is a list of accessibility features in HTML:

5.1 Equivalent information

Checkpoints in this section: 7.1.

User agents must be able to recognize sources of alternative representations of content.

5.1.1 Sources of blinking text and animation

Checkpoints in this section: 5.6 and 5.7.

User agents that recognize the following sources of blinking text and animations must enable users to freeze that text.

In HTML
In CSS
In GIF animated images.
To be completed.

5.1.2 Alternative representations of information for images, video, applets

Checkpoints in this section: 7.4, 7.5.

[Ed. How to handle null/absent alt.]

5.1.3 Textual equivalents for audio and video

Checkpoints in this section: 7.7, 7.10, 6.9

Scenario-video showing professor writing complex equations and graphs on the overhead and discussing them but not describing what he/she actually wrote on the overhead. Without description this would be inaccessible to people with visual impairments. This could be generalize to any video presentation of visually rich or complex information where the visually presented information is critical to the understanding of the presentation.

5.1.4 Auditory equivalents for video

Checkpoints in this section: 7.11.

5.1.5 Frame equivalents

Checkpoints in this section: 5.12 and 5.11.

[Ed. See Scott's suggestions]

  1. In HTML, content of NOFRAMES.
  2. Otherwise, list of frames. Use "title" as name of frame, otherwise "name".

5.1.6 Alternative representations for tables

In HTML, "summary" attribute. Also, the "abbr" attribute for headers (see the section on table cells and headers).

5.2 Links

Checkpoints in this section: 7.12 and 7.13.

[Ed. Talk about CSS pseudo-classes for :hover]

[Ed. Talk about using :before to clearly indicate that something is a link (e.g., 'A:before { content : "LINK:" }')]

5.3 Tables

Tables were designed to structure relationships among data. In visual media, tables are often rendered on a two-dimensional grid, but this is just one possible interpretation of the data. On the Web, the HTML TABLE element has been used more often than not to achieve a formatting effect ("layout tables") rather than as a way to structure true tabular data ("data tables")

Layout tables cause problems for some screen readers and when rendered, confuse users. Even data tables can be difficult to understand for users that browse in essentially one dimension, i.e. for whom tables are rendered serially. Large tables pose particular problems since remembering cell position and header information becomes more difficult as the table grows.

User agents facilitate browsing by providing access to specific table cells and their associated header information. How headers are associated with table cells is markup language-dependent.

Tabular navigation is required by people with visual impairments and some types of learning disabilities to determine the content of a particular cell and spatial relationships between cells (which may convey information). If table navigation is not available users with some types of visual impairments and learning disabilities may not be able to understand the purpose of a table or table cell.

5.3.1 Table rendering

Properly constructed data tables generally have distinct TH head cells and TD data cells. The TD cell content gains implicit identification from TH cells in the same column and/or row.

For layout tables, a user agent can assist the reader by indicating that no relationship between cells should be expected. Authors should not use TH cells just for their formatting purpose in layout tables, as those TH cells imply that some TD cells should gain meaning from the TH cell content.

When a table is "read" from the screen, the contents of multiline cells may become intermingled. For example, consider the following table:

This is the top left cell    This is the top right cell 
of the table.                of the table.

This is the bottom left      This is the bottom right 
cell of the table.           cell of the table.

If read directly from the screen, this table might be rendered as "This is the top left cell This is the top right cell", which would be confusing to the user.

A user agent should provide a means of determining the contents of cells as discrete from neighboring cells, regardless of the size and formatting of the cells. This information is made available through the DOM ([DOM1]).

The contents of a cell in a data table are generally only comprehensible in context (i.e., with associated header information, row/column position, neighboring cell information etc.). User agents should provide users with header information and other contextual agent. Techniques include:

[Ed. Discuss repair strategies for finding header information?]

Since not all tables are designed with the header information, a conforming user agent should provide, as an option, a "best guess" of the header information for a cell. Possible strategies include:

The user may choose the form and amount of this information, possibly announcing the row heads only once and then the column head or its abbreviation ("abbr") to announce the cell content.

[Ed. Define algorithm for finding "header information" here. Does it come from THEAD, TH, attributes, HTML 4.0 algorithm for finding header information, etc. Allow the user to choose either "abbr" or what is calculated by the header algorithm.]

5.3.2 Cell rendering

Non-visual rendering of information by a browser or an assistive technology working through a browser will generally not render more than a single cell, or a few adjacent cells at a time. Because of this, the location of a cell of interest within a large table may be difficult to determine for the users of non-visual rendering.

In order to provide equivalent access to these users, compliant browsers should provide a means of determining the row and column coordinates of the cell having the point of regard via keyboard commands. Additionally, to allow the user of a non-visual rendering technology to return to a cell, the browser should allow a means of moving the point of regard to a cell based on its row and column coordinates.

At the time the user enters a table, or while the point of regard is located within a table, the user agent should allow an assistive technology to provide information to the user regarding the dimensions (in rows and columns) of the table. This information, in combination with the summary, title, and caption, can allow the user with a disability to quickly decide whether to explore the table of skip over it.

Dimensions is an appropriate term, though dimensions needn't be constants. For example a table description could read: "4 columns for 4 rows with 2 header rows. In those 2 header rows the first two columns have "colspan=2". The last two columns have a common header and two subheads. The first column, after the first two rows, contains the row headers.

Some parts of a table may have 2 dimensions, others three, others four, etc. Dimensionality higher than 2 are projected onto 2 in a table presentation.

5.3.3 Cell header algorithm

User agents should use the algorithm to calculate header information provided in the HTML 4.0 specification ([HTML40], section 11.4.3).

[Ed. The following issues were raised by Harvey Bingham.]

  1. TH cells on both the left and right of the table need to be considered.
  2. For TH cells with "rowspan" set: the content of those TH cells must be considered for each of the N-1 rows below the one containing that TH content.
  3. An internal TH in a row surrounded on either side by TDs has no means to specify to which (row or column) that TH overrides what existed to its left or above it.
  4. Finding column header cells assumes they are all above the TD cell to which they apply.
  5. A TH with "colspan" set needs to be included in the list of TH for the M-1 columns to the right of the column in which the TH is found.

5.4 Frames

Checkpoints in this section: 5.12, 6.16, 9.1 9.7, and 9.4

5.4.1 Frame formatting

Checkpoints in this section: 9.1.

Possible solutions:

5.5 Scripts

Checkpoints in this section: 5.8.

Certain elements of the document language may have associated event handlers that are triggered when certain events occur. User agents must be able to identify those elements with event handlers statically associated (i.e., associated in the document source, not in a script).

In HTML
All of the attributes beginning with the prefix "on": "onblur", "onchange", "onclick", "ondblclick", "onkeydown", "onkeypress", "onkeyup", "onload", "onmousedown", "onmousemove", "onmouseout", "onmouseover", "onmouseup", "onreset", "onselect", "onsubmit", and "onunload".
[Ed. Other sources? ]
[Ed. To be completed.]

5.6 Multimedia

[Ed. Talk about EMBED? Charles recommends that it be put inside an OBJECT if used.]

6 Support for CSS accessibility

[Ed. Link to W3C Note on HTML Accessibility Features instead of this section]

Checkpoints in this section: 11.2, 11.1

The following techniques apply to user agents that implement Cascading Style Sheets (see CSS, level 1 and CSS, level 2). Cascading Style Sheets may be part of a source document or linked externally.

Stand-alone style sheets are useful for implementing user profiles in public access computer environments where several people use the same computer. User profiles allow for convenient customization and may be shared by a group.

7 Support for SMIL accessibility

[Ed. Link to W3C Note on HTML Accessibility Features instead of this section]

Checkpoints in this section: 11.2, 11.1

[Ed. Ensure that in SMIL, users can stop temporal links. See proposal from Marja.]

Accessible presentation means here that the information can be easily accessed by using different media and that the user can easily control whether to show the information or not.

8 Appendix: Accessibility features of some operating systems

Several of the more popular mainstream operating systems now include a common suite of built-in accessibility features that are designed to assist individuals with varying abilities. Despite operating systems differences, the built-in accessibility features use a similar naming convention and offer similar functionalities, within the limits imposed by each operating system (or particular hardware platform).

The following is a list of built-in accessibility features from several platforms:

StickyKeys
These allow users to perform a multiple simultaneous key sequence by pressing and releasing each key in sequential order. StickyKeys is designed to work with only those keys defined as modifier keys. Modifier keys are pressed in combination with other keys, to change the outcome of the second (or more) pressed keys. For example, the SHIFT key is defined as a modifier key, since it is commonly used to create upper case characters. Each operating system or hardware platform typically defines a set of keys which can act as modifier keys. The most common modifier keys include SHIFT, CONTROL, and ALTERNATE.
MouseKeys
These allow users to move the mouse cursor and activate the mouse button(s) from the keyboard.
RepeatKeys
These allow users to set how fast a key repeats (e.g., sometimes referred to as typematic rate) when the key is held pressed (e.g., Repeat Rate), and also allows control over how quickly the key starts to repeat after the key has been pressed (e.g., delay Until Repeat). Key repeating may also be eliminated.
SlowKeys
These instruct the computer not to accept a key as pressed until it has been pressed and held down for a specific user adjustable length of time.
BounceKeys
These prevent extra characters from being typed if the user bounces (e.g., tremor) on the same key when pressing or releasing it.
ToggleKeys
These provide an audible indication for the status of keys that have a toggled state (e.g., keys that maintain status after being released). The most common toggling keys include Caps Lock, Num Lock, and Scroll Lock.
SoundSentry
These monitor the operating system and applications for sounds, and attempt to provide a visual indication when a sound is being played. Older versions of Sound Sentry may have flashed the entire display screen for example, while newer versions of SoundSentry provide the user with a selection of options, such as flashing the active window or flashing the active window caption bar.

The next three built in accessibility features are not as commonly available as the above group of features, but are included here for definition, completeness, and future compatibility.

ShowSounds
These are user setting or software switches that are available for the operating system and application (including user agents) APIs to read, to notify them that the user wishes audio information to also be presented in a visual format.
High Contrast
These automatically change the display fonts and colors to choices which should provide for easier reading.
TimeOut
These allow the built-in accessibility features to automatically turn off if the computer is unused for a specified length of time, and is intended for use when the computer is in a public setting (e.g., library). TimeOut might also be referred to as reset or automatic reset.

The next accessibility feature listed here is not considered to be a built in accessibility feature (since it only provides an alternate input channel) and is presented here only for definition, completeness, and future compatibility.

SerialKeys
These allow a user to perform all keyboard and mouse functions from an external assistive device (such as communication aid) communicating with the computer via a serial character stream (e.g., serial port, IR port, etc.) rather than or in conjunction with, the keyboard, mouse, and other standard input devices/methods.

Microsoft Windows 95, Windows 98, and Window NT 4.0

The following accessibility features can be adjusted from the Accessibility Options Control Panel:

Additional accessibility features available in Windows 98:

Magnifier
This is a windowed, screen enlargement and enhancement program used by persons with low vision to magnify an area of the visual display (e.g., by tracking the text cursor, focus, etc.). Magnifier can also invert the colors used by the system within the magnification window.
Accessibility Wizard
This is a setup tool intended to assist a person with making choices which setting up the accessibility features on a workstation.

Apple Macintosh Operating System

The following accessibility features can be adjusted from the Easy Access Control panel (Note: Apple convention uses a space within the accessibility feature names.)

The following accessibility features can be adjusted from the Keyboard Control Panel.

The following accessibility feature can be adjusted from the Sound or Monitors and Sound Control Panel (depends upon which version of the OS).

Additional accessibility features available for the Macintosh OS:

CloseView
This is a full screen, screen enlargement and enhancement program used by persons with low vision to magnify the information on the visual display, and it can also change the colors used by the system.
SerialKeys
This is available as freeware from Apple and several other Web sites.

AccessX, X Keyboard Extension (XKB), and the X Window System

(Note: AccessX became a supported part of the X Window System X Server with the release of the X Keyboard Extension in version X11R6.1)

The following accessibility features can be adjusted from the AccessX graphical user interface X client on some DEC, SUN, and SGI operating systems. Other systems supporting XKB may require the user to manipulate the features via a command line parameter(s).

DOS (Disk Operating System)

The following accessibility features are available from a freeware program called AccessDOS, which is available from several Internet Web sites including IBM, Microsoft, and the Trace Center, for either PC-DOS or MS-DOS versions 3.3 or higher.

9 Appendix: Loading assistive technologies for DOM access

There are several methods for developers to accomplish this. Most of these methods fall into four categories:

  1. Launch the entire AT inside the address space of the (UA) browser
  2. Launch some part of the AT, a piece of stub code, a DLL, a Browser Helper Object [special DLL], etc., inside the address space of the (UA) browser
  3. Write your own combined UA/AT (e.g., pwWebSpeak)
  4. Out-of-process access to the DOM

These methods are ordered as developments within a rapidly changing technology with the most recent advances/methods listed first.

Loading assistive technologies for direct access to User Agent DOMs

Note. This method and the method described in the next section are very similar. What differs is the amount of, or capability of, the AT that actually gets loaded in the same process or address space as the User Agent.)

Access to application specific data across process boundaries might be costly in terms of performance. Therefore, user agents may wish to provide a mechanism to load the entire assistive technology (AT), into the process space of the application as a separate thread with direct access to the DOM.

Determining the Assistive Technologies to load

One technique is to store a reference to an assistive technology in a system registry file or, in the case of Jave, a properties file. Registry files are common among many operating system platforms.

In Windows you have the system registry file. On OS/2 you have the system.ini file and on distributed network client networks you often have a system registry server that an application running on the network client computer can query.

In Java 2, the existence of an "accessibility.properties" file causes the system event queue to examine the file for assistive technologies required for loading. If the file contains a property called "assistive_technologies", it will load all registered assistive technologies and start them on their own thread in the Java Virtual Machine that is a single process. An example entry for Java is as follows:

    assistive_technologies=com.ibm.sns.svk.AccessEngine

In Windows, a similar technique could be followed by storing the name of a Dynamic Link Library (DLL) for an assistive technology in a designated assistive technology key name, AT pair. An example entry for Windows could be as follows:

    HKEY_LOCAL_MACHINE\Software\Accessibility\DOM 
           "ScreenReader, VoiceNavigation"

Attaching the Assistive Technologies to the DOM.

Once the assistive technology is determined from the registry, any user agent on the given operating system can now determine if an assistive technology needs to be loaded with their application and load it.

On a non-Java platform, a technique to do this would be to create a separate thread with a reference to the User Agent's DOM using a Dynamic Link Library (DLL). This new thread will load the DLL and call a specified DLL entry name with a pointer to the DOM interface. The assistive technology's task will then run until such time as is necessary to end communication with the DOM.

Once loaded, the assistive technology can monitor the DOM as needed. The assistive technology has the option of communicating with a main assistive technology of its own and process the DOM as a caching mechanism for the main AT application or be used as a bridge to the DOM for the main assistive technology.

In the future, it will be necessary to provide a more comprehensive reference to the application that not only provides direct access to it's client area DOM, but also multiple DOM's that it is processing and an event model for monitoring them.

Example Technique: Java's Direct Access

Java is a working example where the direct access to application components is performed in a timely manner. Here, an assistive technology running on a separate thread monitors GUI events such as focus changes. Focus changes give the AT notification of which component object has focus. The AT can communicate directly with all components in the application by walking the parent/child hierarchy and connecting to each component's methods and monitor events directly. In this case an AT has direct access to component specific methods as well as those provided for by the Java Accessibility API. There is no reason that a DOM interface to UA components could not be provided

In Java 1.1.x, Sun's Java access utilities load an assistive by monitoring the Java awt.properties file for the presence of assistive technologies and loads them as shown in the folowing code example:

import java.awt.*;
import java.util.*;
      
String atNames = Toolkit.getProperty("AWT.assistive_technologies",null);
if (atNames != null) {
    StringTokenizer parser = new StringTokenizer(atNames," ,");
    String atName;
    while (parser.hasMoreTokens()) {
       atName = parser.nextToken();
       try {
          Class.forName(atName).newInstance();
       } 
       catch (ClassNotFoundException e) {
          throw new AWTError("Assistive Technology not found: " + atName);
       } 
       catch (InstantiationException e) {
          throw new AWTError("Could not instantiate Assistive" + 
                             " Technology: " + atName);
       } 
       catch (IllegalAccessException e) {
          throw new AWTError("Could not access Assistive" + 
                             " Technology: " + atName);
       } catch (Exception e) {
          throw new AWTError("Error trying to install Assistive" + 
                             " Technology: " + atName + " " + e);
       }
    }
}

In the above code example, the function Class.forName(atName).newInstance() creates a new instance of the assistive technology. The constructor for the assistive technology will then be responsible for monitoring application component objects by monitoring system events.

In the following code example, the constructor for the assistive technology "Access Engine," adds a focus change listener using Java accessibility utilities. When the assistive technology is notified of an objects gaining focus it has direct access to that object. If the Object, o, implemented a DOM interface the assistive technology would now have direct access to the DOM in the same process space as the application.

   import java.awt.*;
   import javax.accessibility.*;
   import com.sun.java.accessibility.util.*;
   import java.awt.event.FocusListener;

   class AccessEngine implements FocusListener {
      public AccessEngine() {
         //Add the AccessEngine as a focus change listener
         SwingEventMonitor.addFocusListener((FocusListener)this);
      }
      
      public void focusGained(FocusEvent theEvent) {
         // get the component object source
         Object o = theEvent.getSource();
         // check to see if this is a DOM component
         if (o instanceof DOM) {
            ...
         }
      }
      public void focusLost(FocusEvent theEvent) {
         // Do Nothing
      }
   }

In this example, the assistive technology has the option of running standalone or acting as a cache for a bridge that communicates with a main assistive technology running outside the Java virtual machine.

Loading part of the assistive technologies for direct access to User Agent DOMs

Access to application specific data across process boundaries might be costly in terms of performance. Therefore, user agents may wish to provide a mechanism to load part of the assistive technology (AT) into the process space of the application as a separate thread, with direct access to the DOM, to provide the specific functionality they require. This could consist of a piece of stub code, a DLL, a Browser Helper Object, etc. An example of how to do this follows.

Browser Helper Objects

In order to attach to a running instance of Internet Explorer 4.0, you can use a "Browser Helper Object." A "Browser Helper Object" is a DLL that will attach itself to every new instance of Internet Explorer 4.0 (only if you explicitly run iexplore.exe). You can use this feature to gain access to the object model of a particular running instance of Internet Explorer. You can also use this feature to get events from an instance of Internet Explorer 4.0. This can be tremendously helpful when many method calls need to be made to IE, as each call will be performed much more quickly than the out of process case.

There are some requirements when creating a Browser Helper Object

For more information, please check out:

http://support.microsoft.com/support/kb/articles/Q179/2/30.asp.
http://msdn.microsoft.com/library/techart/bho.htm

Java Access Bridge

In order for native Windows ATs to gain access to Java applications without the creating a Java native solution Sun Microsystems provides the "Java Access Bridge." This bridge is loaded as an AT as described in section 6.1.3. The bridge uses a Java Native Invocation (JNI) to Dynamic Link Library) (DLL) communication and caching mechanism that allows a native assistive technology to gather and monitor accessibility information in the Java environment. In this environment, the AT determines that a Java application or applet is running and communicates with the Java Access Bridge DLL to process accessibility information about the application/applet running in the Java Virtual Machine.

Loading assistive technologies "as" the User Agent with access to the DOMs

Specialized user agents might also include the necessary assistive technology as part of their interface, and thus provide possibly the best of both worlds. An example would be pwWebSpeak, from The Productivity Works (refer to [Prodworks]).

[Ed. Have The Productivity Works provide short description.]

Loading assistive technologies for indirect access to User Agent DOMs

Access to application specific data across process boundaries or address space might be costly in terms of performance. However, there are other reasons to consider when accessing the User Agent DOM that might lead a developer to wish to access the DOM from their own process or memory address space. One obvious protection this method provides, is that if the User Agent application fails, it doesn't disable the user's AT as well. Another consideration would be legacy systems, where the user relies on their AT for access to other applications as well as the User Agent, and thus would have their AT loaded all the time, not just for accessing the User Agent.

There are several ways to gain access to the User Agent's DOM. Most User Agents support some kind of external interface, or act as a mini-server to other applications running on the desktop. Internet Explorer is a good example of this, as IE can behave as a component object model (COM) server to other applications. Mozilla, the open source release of Navigator also supports cross platform COM (XPCOM).

An example of using COM to access the IE Object Model can be seen in the code snippet below. This is an example of how to use COM to get a pointer to the WebBrowser2 module, which in turn allows you to get a interface/pointer to the document object, or IE DOM for the web page in view.

   /* first, get a pointer to the WebBrowser2 control */
   if (m_pIE == NULL) {
      hr = CoCreateInstance(CLSID_InternetExplorer, 
           NULL, CLSCTX_LOCAL_SERVER, IID_IWebBrowser2, 
           (void**)&m_pIE);

      /* next, get a interface/pointer to the document in view, 
         this is an interface to the document object model (DOM)*/

      void CHelpdbDlg::Digest_Document() {
         HRESULT hr;
         if (m_pIE != NULL) {
            IDispatch* pDisp;
            hr = m_pIE->QueryInterface(IID_IDispatch, (void**) &pDisp);
            if (SUCCEEDED(hr)) {
        
               IDispatch* lDisp;
               hr = m_pIE->get_Document(&lDisp);
               if (SUCCEEDED(hr)) {
           
                   IHTMLDocument2* pHTMLDocument2;
                   hr = lDisp->QueryInterface(IID_IHTMLDocument2,
                               (void**) &pHTMLDocument2);
                   if (SUCCEEDED(hr)) {
            
                   /* with this interface/pointer, IHTMLDocument2*,
                      you can then work on the document */
                      IHTMLElementCollection* pColl;
                      hr = pHTMLDocument2->get_all(&pColl);
                      if (SUCCEEDED(hr)) {
                    
                         LONG c_elem;
                         hr = pColl->get_length(&c_elem);
                         if (SUCCEEDED(hr)) {
                            FindElements(c_elem, pColl);
                         }
                         pColl->Release();
                      }
                      pHTMLDocument2->Release();
                   }
                   lDisp->Release();
               }
               pDisp->Release();
            }
         }
      }
   }   

For more information on using COM with IE, please visit the Microsoft web site:

http://www.microsoft.com/com/default.asp

For more information on using XPCOM with Mozilla, please visit the Mozilla web site:

http://www.mozilla.org/

For a working example of the method described in 6.1.4, please visit the following web site and review HelpDB, developed as a testing tool for web table navigation.

http://trace.wisc.edu/world/web/document_access/

10 Appendix: Checkpoint Map

This index lists each checkpoint and the sections in this document where it is discussed. Furthermore, each guideline number links to its definition in the guidelines document. Each checkpoint also links to its definition in the guidelines document.

Guideline 1:

1.1 Ensure that all functionalities offered by the user agent interface are available through all supported input devices. [Priority 1] (Checkpoint 1.1 in guidelines)
Refer to 3.2 Device independence
1.2 Ensure that the user can interact with all active elements of a document in a device-independent manner. [Priority 1] (Checkpoint 1.2 in guidelines)
Refer to 3.2 Device independence
1.3 Ensure that the user can install the user agent software in a device-independent manner. [Priority 1] (Checkpoint 1.3 in guidelines)
Refer to 3.2 Device independence
1.4 Ensure that the user can configure the user agent in a device-independent manner. [Priority 1] (Checkpoint 1.4 in guidelines)
Refer to 3.2 Device independence
1.5 Ensure that the user can access user agent documentation in a device-independent manner. [Priority 1] (Checkpoint 1.5 in guidelines)
Refer to 3.2 Device independence
1.6 Ensure that all messages to the user (e.g., warnings, errors, etc.) are available in an output device-independent manner using any supported output devices. [Priority 1] (Checkpoint 1.6 in guidelines)
Refer to 3.2 Device independence

Guideline 2:

2.1 By default and without additional customization, ensure that all functionalities offered by the user agent are accessible using the keyboard. [Priority 1] (Checkpoint 2.1 in guidelines)
Refer to 3.7 Keyboard access
2.2 Provide documentation on default keyboard commands and include with user agent documentation and/or user help system. [Priority 1] (Checkpoint 2.2 in guidelines)
Refer to 3.7.2 Keyboard shortcuts
2.3 Provide information to the user about the current keyboard configuration. [Priority 1] (Checkpoint 2.3 in guidelines)
Refer to 3.7.2 Keyboard shortcuts
2.4 Allow the user to configure the keystrokes used to activate user agent functionalities. Wherever possible, allow single key activation of functions. [Priority 2] (Checkpoint 2.4 in guidelines)
Refer to 3.8.2 Keyboard configuration
2.5 Allow the user to turn on and off author-specified keyboard configurations. [Priority 2] (Checkpoint 2.5 in guidelines)
Refer to 3.8.2 Keyboard configuration
2.6 Indicate the keyboard access method to activate a user agent function using platform conventions. [Priority 2] (Checkpoint 2.6 in guidelines)
Refer to 3.7.2 Keyboard shortcuts
2.7 Avoid default keyboard configurations that interfere with system conventions. [Priority 2] (Checkpoint 2.7 in guidelines)
Refer to 3.8.2 Keyboard configuration
2.8 Provide a default keyboard configuration for frequently performed operations. [Priority 3] (Checkpoint 2.8 in guidelines)
Refer to 3.8.2 Keyboard configuration

Guideline 3:

3.1 Ensure that all product documentation conforms to the Web Content Accessibility Guidelines. [Priority 1] (Checkpoint 3.1 in guidelines)
Refer to 3.9.2 Accessible documentation
3.2 Ensure that all user agent functionalities that promote accessibility are documented. [Priority 1] (Checkpoint 3.2 in guidelines)
Refer to 3.9 Documentation
3.3 Describe product features known to promote accessibility in a section of the product documentation. [Priority 2] (Checkpoint 3.3 in guidelines)
Refer to 3.9.1 Where to document accessibility

Guideline 4:

4.1 Allow the user to configure the user agent in named profiles that may be shared (by other users or software). [Priority 2] (Checkpoint 4.1 in guidelines)
Refer to 3.8.1 User profiles
4.2 Allow the user to configure the visual arrangement of user interface controls. [Priority 3] (Checkpoint 4.2 in guidelines)
Refer to 3.8.3 User interface

Guideline 5:

5.1 Allow the user to turn on and off rendering of images. [Priority 1] (Checkpoint 5.1 in guidelines)
Refer to 3.3.1 Feature control
5.2 Allow the user to turn on and off rendering of background images. [Priority 1] (Checkpoint 5.2 in guidelines)
Refer to 3.3 User control of style
5.3 Allow the user to turn on and off rendering of video. [Priority 1] (Checkpoint 5.3 in guidelines)
Refer to 3.3.1 Feature control
5.4 Allow the user to turn on and off rendering of sound. [Priority 1] (Checkpoint 5.4 in guidelines)
Refer to 3.3.1 Feature control
5.5 Allow the user to turn on and off rendering of captions. [Priority 1] (Checkpoint 5.5 in guidelines)
Refer to 3.3.1 Feature control
5.6 Allow the user to turn on and off animated or blinking text. [Priority 1] (Checkpoint 5.6 in guidelines)
Refer to 5.1.1 Sources of blinking text and animation
5.7 Allow the user to turn on and off animations and blinking images. [Priority 1] (Checkpoint 5.7 in guidelines)
Refer to 5.1.1 Sources of blinking text and animation
5.8 Allow the user to turn on and off support for scripts and applets. [Priority 1] (Checkpoint 5.8 in guidelines)
Refer to 5.5 Scripts
5.9 Allow the user to turn on and off support for user style sheets. [Priority 1] (Checkpoint 5.9 in guidelines)
Refer to 3.3.1 Feature control
5.10 Allow the user to turn on and off support for author style sheets. [Priority 1] (Checkpoint 5.10 in guidelines)
Refer to 3.3.1 Feature control
5.11 Allow the user to turn on and off support for spawned windows. [Priority 1] (Checkpoint 5.11 in guidelines)
Refer to 5.1.5 Frame equivalents
5.12 Allow the user to turn on and off rendering of frames. [Priority 2] (Checkpoint 5.12 in guidelines)
Refer to 5.1.5 Frame equivalents and
5.4 Frames
5.13 Allow the user to turn on and off author-specified page forwards that occur after a time delay and without user intervention. [Priority 3] (Checkpoint 5.13 in guidelines)
Refer to 3.3.1 Feature control
5.14 Allow the user to turn on and off automatic page refresh. [Priority 3] (Checkpoint 5.14 in guidelines)
Refer to 3.3.1 Feature control

Guideline 6:

6.1 Allow the user to control font family. [Priority 1] (Checkpoint 6.1 in guidelines)
Refer to 3.3 User control of style
6.2 Allow the user to control font size. [Priority 1] (Checkpoint 6.2 in guidelines)
Refer to 3.3 User control of style
6.3 Allow the user to control foreground color. [Priority 1] (Checkpoint 6.3 in guidelines)
Refer to 3.3 User control of style
6.4 Allow the user to control background color. [Priority 1] (Checkpoint 6.4 in guidelines)
Refer to 3.3 User control of style
6.5 Allow the user to control selection highlighting (e.g., foreground and background color). [Priority 1] (Checkpoint 6.5 in guidelines)
Refer to 3.3 User control of style
6.6 Allow the user to control focus highlighting (e.g., foreground and background color). [Priority 1] (Checkpoint 6.6 in guidelines)
Refer to 3.3 User control of style
6.7 Allow the user to control animation rate. [Priority 2] (Checkpoint 6.7 in guidelines)
Refer to 3.3 User control of style
6.8 Allow the user to control video frame rates. [Priority 1] (Checkpoint 6.8 in guidelines)
Refer to 3.3 User control of style
6.9 Allow the user to control the position of captions. [Priority 1] (Checkpoint 6.9 in guidelines)
Refer to 5.1.3 Textual equivalents for audio and video
6.10 Allow the user to start, stop, pause, and rewind video. [Priority 2] (Checkpoint 6.10 in guidelines)
Refer to 3.3 User control of style
6.11 Allow the user to control audio playback rate. [Priority 1] (Checkpoint 6.11 in guidelines)
Refer to 3.3 User control of style
6.12 Allow the user to control audio volume. [Priority 2] (Checkpoint 6.12 in guidelines)
Refer to 3.3 User control of style
6.13 Allow the user to start, stop, pause, and rewind audio. [Priority 2] (Checkpoint 6.13 in guidelines)
Refer to 3.3 User control of style
6.14 Allow the user to control speech playback rate. [Priority 1] (Checkpoint 6.14 in guidelines)
Refer to 3.3 User control of style
6.15 Allow the user to control speech volume, pitch, gender and other articulation characteristics. [Priority 2] (Checkpoint 6.15 in guidelines)
Refer to 3.3 User control of style
6.16 When new windows or user interface components are spawned, allow the user to control window size and position. [Priority 2] (Checkpoint 6.16 in guidelines)
Refer to 3.3 User control of style and
5.4 Frames

Guideline 7:

7.1 Ensure that the user has access to document content, including alternative representations of content. [Priority 1] (Checkpoint 7.1 in guidelines)
Refer to 3.1 Access to content and
5.1 Equivalent information
7.2 For dependent user agents. Ensure that the user has access to the content of an element selected by the user. [Priority 1] (Checkpoint 7.2 in guidelines)
Refer to 3.1 Access to content
7.3 For dependent user agents. Support marked-up changes in natural language of content. For unsupported languages, notify the user of the change. [Priority 2] (Checkpoint 7.3 in guidelines)
Refer to 3.1.1 Changes in content language
7.4 When no alternative text representation has been specified, indicate what type of object is present. [Priority 2] (Checkpoint 7.4 in guidelines)
Refer to 5.1.2 Alternative representations of information for images, video, applets
7.5 When alternative text has been specified explicitly as empty (i.e., an empty string), render nothing. [Priority 3] (Checkpoint 7.5 in guidelines)
Refer to 5.1.2 Alternative representations of information for images, video, applets
7.6 If a technology allows for more than one caption or description track for audio, allow the user to choose from among tracks. [Priority 1] (Checkpoint 7.6 in guidelines)
Refer to 3.3 User control of style
7.7 Allow the user to specify that captions for audio be rendered at the same time as the audio. [Priority 1] (Checkpoint 7.7 in guidelines)
Refer to 5.1.3 Textual equivalents for audio and video
7.8 If a technology allows for more than one caption or description track (e.g., text, video of sign language, etc.) for video, allow the user to choose from among tracks. [Priority 1] (Checkpoint 7.8 in guidelines)
Refer to 3.3 User control of style
7.9 If a technology allows for more than one audio track for video, allow the user to choose from among tracks. [Priority 1] (Checkpoint 7.9 in guidelines)
Refer to 3.3 User control of style
7.10 Allow the user to specify that text descriptions of video be rendered at the same time as the video. [Priority 1] (Checkpoint 7.10 in guidelines)
Refer to 5.1.3 Textual equivalents for audio and video
7.11 Allow the user to specify that auditory descriptions of video be rendered at the same time as the video. [Priority 1] (Checkpoint 7.11 in guidelines)
Refer to 5.1.4 Auditory equivalents for video
7.12 Provide a mechanism (e.g., through style sheets) to distinguish visited links from unvisited links. [Priority 3] (Checkpoint 7.12 in guidelines)
Refer to 5.2 Links
7.13 Allow the user to specify (e.g., through style sheets) that images used in links must have borders. [Priority 3] (Checkpoint 7.13 in guidelines)
Refer to 5.2 Links

Guideline 8:

8.1 Allow the user to navigate views (notably those with frame viewports). [Priority 1] (Checkpoint 8.1 in guidelines)
Refer to 3.5.5 View navigation
8.2 Keep track of the user's point of regard in each view and restore it when the user returns to the view. [Priority 1] (Checkpoint 8.2 in guidelines)
Refer to 3.4.2 Tracking selection and focus
8.3 For dependent user agents. Allow the user to navigate among table cells of a table (notably left and right within a row and up and down within a column). [Priority 1] (Checkpoint 8.3 in guidelines)
Refer to 3.5.3 Table navigation
8.4 Allow the user to navigate among all active elements in the document. [Priority 2] (Checkpoint 8.4 in guidelines)
Refer to 3.5.1 Navigation of active elements
8.5 Allow the user to search for rendered text content, including alternative text content. [Priority 2] (Checkpoint 8.5 in guidelines)
Refer to 3.5.4 Searching
8.6 Allow the user to navigate the document structure. [Priority 2] (Checkpoint 8.6 in guidelines)
Refer to 3.5.2 Navigation of document structure
8.7 Allow the user to configure structured navigation. [Priority 3] (Checkpoint 8.7 in guidelines)
Refer to 3.5 Navigation and searching

Guideline 9:

9.1 Provide a mechanism for highlighting and identifying (through a standard interface where available) the current view. [Priority 1] (Checkpoint 9.1 in guidelines)
Refer to 5.4 Frames
9.2 Provide a mechanism for highlighting and identifying (through a standard interface where available) the user selection. [Priority 1] (Checkpoint 9.2 in guidelines)
Refer to 3.4.1 Highlighting selection and focus
9.3 Provide a mechanism for highlighting and identifying (through a standard interface where available) the current focus. [Priority 1] (Checkpoint 9.3 in guidelines)
Refer to 3.4.1 Highlighting selection and focus
9.4 For dependent user agents. Provide the user with information about the number of viewports. [Priority 2] (Checkpoint 9.4 in guidelines)
Refer to 3.6.2 Document content and
5.4 Frames
9.5 Ensure that when the selection changes, it is in the viewport after the change. [Priority 2] (Checkpoint 9.5 in guidelines)
Refer to 3.4.2 Tracking selection and focus
9.6 Ensure that when the focus changes, it is in the viewport after the change. [Priority 2] (Checkpoint 9.6 in guidelines)
Refer to 3.4.2 Tracking selection and focus
9.7 Identify a frame selected by the user. [Priority 2] (Checkpoint 9.7 in guidelines)
Refer to 3.6.7 Frames and
5.4 Frames
9.8 For dependent user agents. Allow the user to view a document outline constructed from its structural elements (e.g., from header and list elements). [Priority 2] (Checkpoint 9.8 in guidelines)
Refer to 3.5.5 View navigation
9.9 Make available the primary language of a document's content. [Priority 3] (Checkpoint 9.9 in guidelines)
Refer to 3.6.2 Document content
9.10 Make available the number of links (to distinct targets) in a document. [Priority 3] (Checkpoint 9.10 in guidelines)
Refer to 3.6.2 Document content and
3.6.3 Links
9.11 Make available the number of visited links (to distinct targets) in a document. [Priority 3] (Checkpoint 9.11 in guidelines)
Refer to 3.6.2 Document content
9.12 Make available the number of tables in a document. [Priority 3] (Checkpoint 9.12 in guidelines)
Refer to 3.6.2 Document content
9.13 Make available the number of form controls in a document. [Priority 3] (Checkpoint 9.13 in guidelines)
Refer to 3.6.2 Document content
9.14 Make available what portion of the document has loaded. [Priority 3] (Checkpoint 9.14 in guidelines)
Refer to 3.6.1 Document status information
9.15 Identify a link selected by the user. [Priority 3] (Checkpoint 9.15 in guidelines)
Refer to 3.6.3 Links
9.16 Make available whether a chosen link (target) has already been visited. [Priority 3] (Checkpoint 9.16 in guidelines)
Refer to 3.6.3 Links
9.17 Make available whether a chosen link (target) is local to the document. [Priority 3] (Checkpoint 9.17 in guidelines)
Refer to 3.6.3 Links
9.18 Make available whether following a link will involve a fee. [Priority 3] (Checkpoint 9.18 in guidelines)
Refer to 3.6.3 Links
9.19 Identify a table selected by the user. [Priority 3] (Checkpoint 9.19 in guidelines)
Refer to 3.6.4 Tables
9.20 Make available the dimensions of a chosen table. [Priority 3] (Checkpoint 9.20 in guidelines)
Refer to 3.6.4 Tables
9.21 For dependent user agents. Provide access to header information for a table cell selected by the user. [Priority 1] (Checkpoint 9.21 in guidelines)
Refer to 3.6.5 Table cells
9.22 Identify the table containing a table cell selected by the user. [Priority 3] (Checkpoint 9.22 in guidelines)
Refer to 3.6.5 Table cells
9.23 Make available the coordinates in the current table of a selected table cell. [Priority 3] (Checkpoint 9.23 in guidelines)
Refer to 3.6.5 Table cells
9.24 Provide the user with access to any label explicitly associated with a form control. [Priority 2] (Checkpoint 9.24 in guidelines)
Refer to 3.6.6 Form controls
9.25 Maintain consistent user agent behavior and default configurations between software releases. Consistency is less important than accessibility and adoption of system conventions. [Priority 3] (Checkpoint 9.25 in guidelines)
Refer to 3.7.3 Software consistency

Guideline 10:

10.1 Provide information about document changes (to the user and through programming interfaces). [Priority 1] (Checkpoint 10.1 in guidelines)
Refer to 3.6.8 Scripts
10.2 Allow the user to configure the user agent for notification of certain types of document changes only. [Priority 3] (Checkpoint 10.2 in guidelines)
Refer to 3.6.8 Scripts
10.3 Notify the user when enough of the document has loaded in order to begin to browse. [Priority 3] (Checkpoint 10.3 in guidelines)
Refer to 3.6.1 Document status information
10.4 Notify the user when document loading has stalled. [Priority 3] (Checkpoint 10.4 in guidelines)
Refer to 3.6.1 Document status information
10.5 Allow the user to request to be prompted before a form is submitted. [Priority 3] (Checkpoint 10.5 in guidelines)
Refer to 3.6.6 Form controls

Guideline 11:

11.1 Implement the accessibility features defined for supported technologies. [Priority 1] (Checkpoint 11.1 in guidelines)
Refer to 5 Support for HTML accessibility and
6 Support for CSS accessibility and
7 Support for SMIL accessibility
11.2 Support appropriate W3C Recommendations. [Priority 2] (Checkpoint 11.2 in guidelines)
Refer to 5 Support for HTML accessibility and
6 Support for CSS accessibility and
7 Support for SMIL accessibility

Guideline 12:

12.1 Use and provide accessible interfaces to other technologies. [Priority 1] (Checkpoint 12.1 in guidelines)
Refer to 4.3 Accessibility interfaces
12.2 Provide programmatic read and write access to user agent functionalities and user interface controls (including selection and focus) by using operating system and development language accessibility resources and conventions. [Priority 1] (Checkpoint 12.2 in guidelines)
Refer to 4.3 Accessibility interfaces
12.3 Notify dependent user agents of changes to the document and user interface controls (including selection and focus) by using operating system and development language accessibility resources and conventions. [Priority 1] (Checkpoint 12.3 in guidelines)
Refer to 4.3 Accessibility interfaces
12.4 For desktop graphical browsers. Comply with W3C Document Object Model specifications and export interfaces defined by those specifications. [Priority 1] (Checkpoint 12.4 in guidelines)
Refer to 4.4 The document object model
12.5 For desktop graphical browsers. Provide programmatic exchange of information in a timely manner. [Priority 2] (Checkpoint 12.5 in guidelines)
Refer to 4.3 Accessibility interfaces
12.6 Follow operating system conventions and accessibility settings. In particular, follow conventions for user interface design, default keyboard configuration, product installation, and documentation. [Priority 2] (Checkpoint 12.6 in guidelines)
Refer to 4.1 System conventions

Acknowledgments

Many thanks to the following people who have contributed through review and comment: Paul Adelson, James Allan, Denis Anson, Kitch Barnicle, Harvey Bingham, Olivier Borius, Judy Brewer, Bryan Campbell, Kevin Carey, Wendy Chisholm, David Clark, Chetz Colwell, Wilson Craig, Nir Dagan, Daniel Dardailler, B. K. Delong, Neal Ewers, Geoff Freed, John Gardner, Al Gilman, Larry Goldberg, John Grotting, Markku Hakkinen, Earle Harrison, Chris Hasser, Kathy Hewitt, Philipp Hoschka, Masayasu Ishikawa, Phill Jenkins, Jan Kärrman (for help with html2ps), Leonard Kasday, George Kerscher, Marja-Riitta Koivunen, Josh Krieger, Catherine Laws, Greg Lowney, Scott Luebking, William Loughborough, Napoleon Maou, Charles McCathieNevile, Masafumi Nakane, Mark Novak, Charles Oppermann, Mike Paciello, David Pawson, Michael Pederson, Helen Petrie, David Poehlman, Michael Pieper, Jan Richards, Hans Riesebos, Joe Roeder, Lakespur L. Roca, Greg Rosmaita, Lloyd Rutledge, Liam Quinn, T.V. Raman, Robert Savellis, Rich Schwerdtfeger, Constantine Stephanidis, Jim Thatcher, Jutta Treviranus, Claus Thogersen, Steve Tyler, Gregg Vanderheiden, Jaap van Lelieveld, Jon S. von Tetzchner, Willie Walker, Ben Weiss, Evan Wies, Chris Wilson, Henk Wittingen, and Tom Wlodkowski,

References

[CSS1]
"CSS, level 1 Recommendation", B. Bos, H. Wium Lie, eds. The CSS1 Recommendation is:
http://www.w3.org/TR/1999/REC-CSS1-19990111.
[CSS2]
"CSS, level 2 Recommendation", B. Bos, H. Wium Lie, C. Lilley, and I. Jacobs, eds. The CSS2 Recommendation is:
http://www.w3.org/TR/1998/REC-CSS2-19980512.
[DOM1]
"Document Object Model (DOM) Level 1 Specification", V. Apparao, S. Byrne, M. Champion, S. Isaacs, I. Jacobs, A. Le Hors, G. Nicol, J. Robie, R. Sutor, C. Wilson, and L. Wood, eds. The DOM Level 1 Recommendation is:
http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001.
[HTML40]
"HTML 4.0 Recommendation", D. Raggett, A. Le Hors, and I. Jacobs, eds. The HTML 4.0 Recommendation is:
http://www.w3.org/TR/1998/REC-html40-19980424.
[HTML32]
"HTML 3.2 Recommendation", D. Raggett, ed. The HTML 3.2 Recommendation is:
http://www.w3.org/TR/REC-html32.
[MATHML]
"Mathematical Markup Language", P. Ion and R. Miner, eds. The MathML 1.0 Recommendation is:
http://www.w3.org/TR/1998/REC-MathML-19980407.
[RFC2119]
"Key words for use in RFCs to Indicate Requirement Levels", S. Bradner, March 1997. Available at http://www.ietf.org/rfc/rfc2119.txt
[SMIL]
"Synchronized Multimedia Integration Language (SMIL) 1.0 Specification", P. Hoschka, editor. The SMIL 1.0 Recommendation is:
http://www.w3.org/TR/1998/REC-smil-19980615
[UA-TECHNIQUES]
"Techniques for User Agent Accessibility Guidelines 1.0", J. Gunderson, I. Jacobs, eds. This document explains how to implement the checkpoints defined in "User Agent Accessibility Guidelines 1.0". The latest draft of the techniques is available at: http://www.w3.org/WAI/UA/WAI-USERAGENT-TECHS/
[WAI-AUTOOLS]
"Authoring Tool Accessibility Guidelines", J. Treviranus, J. Richards, I. Jacobs, C. McCathieNevile, eds. The latest Working Draft of these guidelines for designing accessible authoring tools is available at:
http://www.w3.org/TR/WD-WAI-AUTOOLS/
[WAI-WEBCONTENT]
"Web Content Accessibility Guidelines", W. Chisholm, G. Vanderheiden, and I. Jacobs, eds., 5 May 1999. This W3C Recommendation is http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505.
[XML]
"Extensible Markup Language (XML) 1.0.", T. Bray, J. Paoli, C.M. Sperberg-McQueen, eds. The XML 1.0 Recommendation is:
http://www.w3.org/TR/1998/REC-xml-19980210

Services

Note. W3C cannot maintain stability for any of the following references outside of its control. These references are included for convenience.

[APPLE-HI]
Information on accessibility guidelines for Macintosh applications. Information on Apple's scripting model can be found at tn1095 and tn1164. Refer also to the Inside Macintosh chapter devoted to Interapplication Communication.
[ED-DEPT]
"Requirements for Accessible Software Design", US Department of Education, version 1.1 March 6, 1997.
[EITAAC]
"EITAAC Desktop Software standards", Electronic Information Technology Access Advisory (EITAAC) Committee.
[IBM-ACCESS]
"Software Accessibility" IBM Special Needs Systems.
[ICCCM]
"The Inter-Client communication conventions manual". A protocol for communication between clients in the X Window system.
[ICE-RAP]
"An ICE Rendezvous Mechanism for X Window System Clients", W. Walker. A description of how to use the ICE and RAP protocols for X Window clients.
[JAVA-ACCESS]
"IBM Guidelines for Writing Accessible Applications Using 100% Pure Java", R. Schwerdtfeger, IBM Special Needs Systems. Available at: http://www.austin.ibm.com/sns/snsjavag.htm
[JAVAAPI]
Information on Java Accessibility API can be found at Java Accessibility Utilities.
[JAVA-CHECKLIST]
"Java Accessibility Guidelines and Checklist". IBM Special Needs Systems.
[JAVA-TUT]
"The Java Tutorial. Trail: Creating a GUI with JFC/Swing". An online tutorial that describes how to use the Swing Java Foundation Class to build an accessible User Interface.
[MSAA]
Information on active accessibility can be found at the Microsoft WWW site on Active Accessibility.
[MS-ENABLE]
Information on accessibility guidelines for Windows applications.
[MS-SOFTWARE]
"The Microsoft Windows Guidelines for Accessible Software Design". Note. This is a "self-extracting archive", an application that will probably only run on MS-Windows systems.
[NOTES-ACCESS]
"Lotus Notes Accessibility Guidelines" IBM Special Needs Systems.
[Prodworks]
The Productivity Works.
[SUN-DESIGN]
"Designing for Accessibility", Eric Bergman and Earl Johnson. This paper discusses specific disabilities including those related to hearing, vision, and cognitive function.
[SUN-HCI]
"Towards Accessible Human-Computer Interaction", Eric Bergman, Earl Johnson, Sun Microsytems 1995. A substantial paper, with a valuable print bibliography.
[TRACE-REF]
"Application Software Design Guidelines" compiled by G. Vanderheiden. A thorough reference work.
[WHAT-IS]
"What is Accessible Software", James W. Thatcher, Ph.D., IBM, 1997. This paper gives a short example-based introduction to the difference between software that is accessible, and software that can be used by some assistive technologies.
[XGuidelines]
Information on accessibility guidelines for Unix and X Window applications. The Open Group has various guides that explain the Motif and Common Desktop Environment (CDE) with topics like how users interact with Motif/CDE applications and how to customize these environments. Note. In X, the terms client and server are used differently from their use when discussing the Web.