W3C

User Agent Accessibility Guidelines 2.0

Editor's Draft 7 November 2007

This version:
http://www.w3.org/WAI/UA/2007/WD-UAAG20-20071107/WD-UAAG20-20071107.html
Latest version:
N/A
Previous version:
http://www.w3.org/WAI/UA/2007/WD-UAAG20-20071106/WD-UAAG20-20071106.html
Editors:
James Allan, Texas School for the Blind and Visually Impaired
Jan Richards, Adaptive Technology Resource Centre, University of Toronto
Previous Editors:
NA

Editing Styles:

Guideline 1. Support input and output device-independence

Checkpoints: 1.1, 1.2, 1.3

Ensure that the user can interact with the user agent (and the content it renders) through different input and output devices.

Since people use a variety of devices for input and output, user agent developers need to ensure redundancy in the user interface. The user may have to operate the user interface with a variety of input devices (e.g., keyboard, pointing device, and voice input) and output modalities (e.g., graphical, speech, or braille rendering).

Enabling full user agent operation through the keyboard is an important part of promoting device-independence in target user agents. In addition to the fact that most operating environments include support for some form of keyboard, the reasons for this include:

While this document only requires keyboard operation for conformance, it promotes input device independence by also allowing people to claim conformance for full pointing device support or full voice support.

As a way to promote output device independence, this guideline requires support for text messages in the user interface because text may be rendered visually, as synthesized speech, or as braille.

The API requirements of guideline 6 also promote device independence by ensuring communication with other software, including assistive technologies.

Checkpoint definitions

1.1 Full keyboard access (P1) Techniques for checkpoint 1.1

@@7.2, 7.4 Possibly move here@@

@@CL: "Precedence of 'operations' - keys"

Level A Success Criteria for Guideline 1.X
Level AA Success Criteria for Guideline 1.X
Level AAA Success Criteria for Guideline 1.X
Normative inclusions and exclusions
  1. This checkpoint excludes the requirements of checkpoint 1.2.
  2. Conformance detail: For both content and user agent

Note: For example, ensure that the user can interact with enabled elements, select content, navigate viewports, configure the user agent, access documentation, install the user agent, and operate user interface controls, all entirely through keyboard input.

User agents generally support at least three types of keyboard operation:

  1. Direct (e.g., keyboard shortcuts such as "F1" to open the help menu; see checkpoint 11.4 for single-key access requirements),
  2. Sequential (e.g., navigation through cascading menus), and
  3. Spatial (e.g., when the keyboard is used to move the pointing device in two-dimensional visual space to manipulate a bitmap image).

User agents should support direct or sequential keyboard operation for all functionalities. Furthermore, the user agent should satisfy this checkpoint by offering a combination of keyboard-operable user interface controls (e.g., keyboard operable print menus and settings) and direct keyboard shortcuts (e.g., to print the current page).

It is also possible to claim conformance to this document for full support through pointing device input and/or voice input. See the section on Input modality labels.

1.2 Manage event handlers (P1) Techniques for checkpoint 1.2
  1. Allow the user to activate, through keyboard input alone, all input device event handlers that are explicitly associated with the element designated by the content focus.
  2. Allow configuration so that moving the content focus to or from an enabled element does not automatically activate any explicitly associated event handlers of any event type. @@moved from 9.5@@
  3. For the element with content focus, make available the list of input device event types for which there are event handlers explicitly associated with the element.@@moved from 9.6@@
  4. In order to satisfy provision one of this checkpoint, the user must be able to activate as a group all event handlers of the same input device event type. For example, if there are 10 handlers associated with the onmousedown event type, the user must be able to activate the entire group of 10 through keyboard input alone, and must not be required to activate each handler separately.
Normative inclusions and exclusions
  1. Provision one of this checkpoint applies to handlers of any input device event type, including event types for keyboard, pointing device, and voice input.
  2. The user agent is not required to allow activation of event handlers associated with a given device (e.g., the pointing device) in any order other than what the device itself allows (e.g., a mouse down event followed by a mouse drag event followed by a mouse up event).
  3. The requirements for this checkpoint refer to any explicitly associated input device event handlers associated with an element, independent of the input modalities for which the user agent conforms. For example, suppose that an element has an explicitly associated handler for pointing device events. Even when the user agent only conforms for keyboard input (and does not conform for the pointing device, for example), this checkpoint requires the user agent to allow the user to activate that handler with the keyboard.
  4. This checkpoint is mutually exclusive of checkpoint 1.1 since the current checkpoint may be excluded from a conformance profile, unlike other keyboard operation requirements.
  5. Conformance profile labels: Events

Note: Refer to the checkpoints of guideline 9 for more information about focus requirements.

1.3 Provide text messages (P1) Techniques for checkpoint 1.3
  1. Ensure that every message (e.g., prompt, alert, or notification) that is a non-text element and is part of the user agent user interface has a text equivalent.
  2. Allow configuration not to render non-essential or low priority text messages based on priority properties defined by the author.

Note: For example, if the user is alerted of an event by an audio cue, a visually-rendered text equivalent in the status bar could satisfy this checkpoint. Per checkpoint 6.5, a text equivalent for each such message must be available through an API. See also checkpoint 6.6 for requirements for programmatic notification of changes to the user interface. Examples of priority properties for a text message are off (not currently live), polite (low priority), assertive (medium priority), and rude (high priority) for AJAX live regions.

Guideline 2. Ensure user access to all content @@skipped all of GL2@@

Checkpoints: 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.10

Ensure that users have access to all content, notably conditional content that may have been provided to meet the requirements of the Web Content Accessibility Guidelines 2.0 [WCAG20].

The checkpoints in this section require the user agent to provide access to all content through a series of complementary mechanisms designed so that if one fails, another will provide some access. The following preferences are embodied in the checkpoints:

Authors may use the conditional content mechanisms of a specification to satisfy the requirements of the Web Content Accessibility Guidelines 2.0 [WCAG20]. Ensuring access to conditional content benefits all users since some users may not have access to some content due to a technological limitation (e.g., their mobile browser cannot display graphics) or a configuration preference (e.g., they have a slow Internet connection and prefer not to download movies or images).

Checkpoint definitions

2.1 Render content according to specification (P1) Techniques for checkpoint 2.1
  1. Render content according to format specification (e.g., for a markup language or style sheet language).
Normative inclusions and exclusions
  1. Rendering requirements include format-defined interactions between author preferences and user preferences/capabilities (e.g., when to render the alt attribute in HTML, the rendering order of nested OBJECT elements in HTML, test attributes in SMIL, and the cascade in CSS2).
  2. When a rendering requirement of another specification contradicts a requirement of UAAG 1.0, the user agent may disregard the rendering requirement of the other specification and still satisfy this checkpoint; see the section on the relation of this document to general software design guidelines and other specifications for more information.
  3. The user agent is not required to satisfy this checkpoint for all implemented specifications; see the section on conformance profiles for more information.
  4. This checkpoint excludes the requirements of checkpoint 2.6.

Note: If a conforming user agent does not render a content type, it should allow the user to choose a way to handle that content (e.g., by launching another application or by saving it to disk).

2.2 Provide text view (P1) Techniques for checkpoint 2.2
  1. For content authored in text formats, provide a view of the text source.
Normative inclusions and exclusions
  1. For the purposes of this checkpoint, a text format is:
    • any media object given an Internet media type of "text" (e.g., "text/plain", "text/html", or "text/*") as defined in RFC 2046 [RFC2046], section 4.1, or
    • any media object identified by Internet media type to be an XML document (as defined in [XML], section 2) or SGML application. Refer, for example, to Internet media types defined in "XML Media Types" [RFC3023].
  2. The user agent is only required to satisfy this checkpoint for text formats that are part of a conformance claim; see the section on conformance profiles for more information. However, user agents should provide a text view for all implemented text formats.
2.3 Render conditional content (P1) Techniques for checkpoint 2.3

X-Multiple Cond Content?
Physically bigger, smaller, not physical (e.g sound)?
Some play together. Some don't.
X-user cannot deal with base content
X-want access to any and all replacement content
X-move between them
X-configure a default replacement
X-without refreshing page, go back to base content
X-User Agent may not be able to load content

  1. The user should be able to have access to any items in a "conditional content stack" (defn: various pieces of content that are provided for a given position in content - the piece may be mutually exclusive (e.g., regular contrast graphic, high contrast graphic) or non-exclusive (e.g., sound track and caption track ) that the user agent can understand.
  2. Given a stack, the user preferred items should be rendered first.
  3. User should be alerted to the presence of other non-rendered items in the stack.
  4. For onscreen user agents, if the conditional content has larger onscreen dimensions than the top item in the stack, the a configuration should control whether the dimensions are ignored
  5. If the conditional content is plain text then the user should have the option of having it available programmatically but not onscreen.

 

  1. The user should be able to access all pieces of conditional content "C".
  2. Configure to choose your preferred conditional content.
  3. When a technology specification does not explain how to provide access to conditional content:
Sufficient techniques
  1. To satisfy provision one of this checkpoint, the configuration may be a switch that, for all content, turns on or off the access mechanisms described in provision two.
  2. To satisfy provision two of this checkpoint, the user agent may provide access on a per-element basis (e.g., by allowing the user to query individual elements) or for all elements (e.g., by offering a configuration to render conditional content all the time).
  3. To satisfy the requirement of provision two of this checkpoint to allow the user to view the content associated with each placeholder, the user agent may either render the associated content in a separate viewport or in place of the placeholder.
Normative inclusions and exclusions
  1. For the placeholder requirement of provision two of this checkpoint, a request to view the original content associated with a placeholder is considered an explicit user request to render that content.
  2. The user agent is not required to include placeholders in the document object. A placeholder that is part of the document object should conform to the Web Content Accessibility Guidelines 2.0 [WCAG20]. If a placeholder is not part of the document object, it is part of the user interface only (and subject, for example, to checkpoint 1.3).
  3. Conformance detail: For all content

Note: For instance, an HTML user agent might allow users to query each element for access to conditional content supplied for the alt, title, and longdesc attributes. Or, the user agent might allow configuration so that the value of the alt attribute is rendered in place of all IMG elements (while other conditional content might be made available through another mechanism). User agents should expose configuration choices in as highly visible a fashion as is practical such as on a menu entry or dialog settings devoted to accessibility.

2.4 Allow time-independent interaction (P1) Techniques for checkpoint 2.4
  1. For rendered content where user input is only possible within a finite time interval controlled by the user agent, allow configuration to provide a view where user interaction is time-independent.
Sufficient techniques
  1. The user agent may satisfy this checkpoint by pausing processing automatically to allow for user input, and resuming processing on explicit user request. When using this technique, pause at the end of each time interval where user input is possible. In the paused state:
    • Alert the user that the rendered content has been paused (e.g., highlight the pause button in a multimedia player's control panel).
    • Highlight which enabled elements are time-sensitive.
    • Allow the user to interact with the enabled elements.
    • Allow the user to resume on explicit user request (e.g., by pressing the play button in a multimedia player's control panel; see also checkpoint 4.5).
  2. The user agent may satisfy this checkpoint by generating a time-independent (or, "static") view, based on the original content, that offers the user the same opportunities for interaction. The static view should reflect the structure and flow of the original time-sensitive presentation; orientation cues will help users understand the context for various interaction opportunities.
Normative inclusions and exclusions
  1. When satisfying this checkpoint for a real-time presentation, the user agent may discard packets that continue to arrive after the construction of the time-independent view (e.g., when paused or after the construction of a static view).
  2. This checkpoint does not apply when the user agent cannot recognize the time interval in the presentation format, or when the user agent cannot control the timing (e.g., because it is controlled by the server).

Note: If the user agent satisfies this checkpoint by pausing automatically, it may be necessary to pause more than once when there are multiple opportunities for time-sensitive user interaction. When pausing, pause synchronized content as well (whether rendered in the same or different viewports) per checkpoint 2.6. In SMIL 1.0 [SMIL], for example, the begin, end, and dur attributes synchronize presentation components. See also checkpoint 3.4, which involves client-driven content retrieval.

2.5 Make captions, transcripts, audio descriptions available (P1) Techniques for checkpoint 2.5
  1. Allow configuration or control to render text transcripts, collated text transcripts, captions, and audio descriptions in content at the same time as the associated audio tracks and visual tracks.
Normative inclusions and exclusions
  1. Conformance profile labels: Video, Audio
  2. Conformance detail: For all content
2.6 Respect synchronization cues (P1) Techniques for checkpoint 2.6
  1. Respect synchronization cues (e.g., in markup) during rendering.
Normative inclusions and exclusions
  1. This checkpoint is mutually exclusive of checkpoint 2.1 since it may be excluded from a conformance profile.
  2. Conformance profile labels: Video, Audio
2.7 Repair missing content (P2) Techniques for checkpoint 2.7
  1. Allow configuration to generate repair text when the user agent recognizes that the author has not provided conditional content required by the format specification.
Sufficient techniques
  1. The user agent may satisfy this checkpoint by basing the repair text on any of the following available sources of information: URI reference (as defined in [RFC2396], section 4), content type, or element type. Note, however, that additional information that would enable more helpful repair might be available but not "near" the missing conditional content. For instance, instead of generating repair text on a simple URI reference, the user agent might look for helpful information near a different instance of the URI reference in the same document object, or might retrieve useful information (e.g., a title) from the resource designated by the URI reference.
Normative inclusions and exclusions
  1. Conformance detail: For all content

Note: Some markup languages (such as HTML 4 [HTML4] and SMIL 1.0 [SMIL] require the author to provide conditional content for some elements (e.g., the alt attribute on the IMG element).

2.8 No repair text (P3) Techniques for checkpoint 2.8
  1. Allow at least two configurations for when the user agent recognizes that conditional content required by the format specification is present but empty content:
Normative inclusions and exclusions
  1. Conformance detail: For all content

Note: In some authoring scenarios, empty content (e.g., alt="" in HTML) may make an appropriate text equivalent, such as when non-text content has no other function than pure decoration, or when an image is part of a "mosaic" of several images and does not make sense out of the mosaic. Refer to the Web Content Accessibility Guidelines 2.0 [WCAG20] for more information about text equivalents.

2.9 Render conditional content automatically (P3) Techniques for checkpoint 2.9
  1. Allow configuration to render all conditional content automatically.
  2. As part of satisfying provision one of this checkpoint, provide access according to specification, or where unspecified, by applying one of the techniques 1a, 2a, or 1b defined in provision two of checkpoint 2.3.
Sufficient techniques
  1. The user agent may satisfy provision one of this checkpoint through multiple configurations (e.g., a first configuration to render one type of conditional content automatically and a second to render another type).
Normative inclusions and exclusions
  1. The user agent is not required to render all conditional content at the same time in a single viewport.
  2. Conformance detail: For all content

Note: For instance, an HTML user agent might allow configuration so that the value of the alt attribute is rendered in place of all IMG elements (while other conditional content might be made available through another mechanism).

2.10 Don't render text in unsupported writing systems (P3) Techniques for checkpoint 2.10
  1. For graphical user agents, allow configuration not to render text in unsupported scripts (i.e., writing systems) when that text would otherwise be rendered.
  2. When configured per provision one of this checkpoint, indicate to the user in context that author-supplied content has not been rendered due to lack of support for a writing system.
Normative inclusions and exclusions
  1. This checkpoint does not require the user agent to allow different configurations for different writing systems.

Note: The primary purpose of this checkpoint is to benefit users with serial access to content or who navigate sequentially, allowing them to skip portions of content that would be unusable if rendered graphically as "garbage."

Guideline 3. Allow configuration not to render some content that may reduce accessibility

Checkpoints: 3.1, 3.2, 3.3, 3.4, 3.5

Ensure that the user may turn off rendering of content (e.g., audio, video, scripts) that may reduce accessibility by obscuring other content or disorienting the user.

Some content or behavior specified by the author may make the user agent unusable or may obscure information. For instance, flashing content may trigger seizures in people with photosensitive epilepsy, or may make a Web page too distracting to be usable by someone with a cognitive disability. Blinking text can affect screen reader users, since screen readers (in conjunction with speech synthesizers or braille displays) may re-render the text every time it blinks. Distracting background images, colors, or sounds may make it impossible for users to see or hear other content. Dynamically changing Web content may cause problems for some assistive technologies. Scripts that cause unanticipated changes (e.g., viewports that open without notice or automatic content retrieval) may disorient some users with cognitive disabilities.

This guideline requires the user agent to allow configuration so that, when loading Web resources, the user agent does not render content in a manner that might pose accessibility problems. Requirements for interactive control of rendered content are part of guideline 4.

Checkpoint definitions

3.1 Toggle background images (P1) Techniques for checkpoint 3.1
  1. Allow configuration not to render images that are rendered on the base background.
Sufficient techniques
  1. Allowing users to turn off images that the user agent would render on the base background.
Normative inclusions and exclusions
  1. This checkpoint must be satisfied for all implemented image specifications; see the section on conformance profiles.
  2. When configured not to render background images, the user agent is not required to retrieve them until the user requests them explicitly. When background images are not rendered, user agents should render a solid background color instead; see checkpoint 4.3 for information about text colors.
  3. This checkpoint only requires control of background images for "two-layered" renderings, where the background is considered the first layer and everything rendered above it is considered the second layer.
  4. Conformance profile labels: Image

Note: When background images are not rendered, they are considered conditional content. See checkpoint 2.3 for information about providing access to conditional content.

3.2 Toggle audio, video, animated images, and animated/blinking text (P1) Techniques for checkpoint 3.2
  1. Allow configuration not to render audio, video, or animated image content, except on explicit user request.
  2. Allow configuration to render animated or blinking text content as motionless, unblinking text.
Sufficient techniques
  1. The user agent may satisfy the first success criteria by making video and animated images invisible and audio silent, but this technique is not recommended.
  2. The user agent may satisfy the second success criteria by showing still images in place of video and image animations. @@Still issues with this@@
  3. The user must still have access to all animated/blinking text content, but the user agent may render it in a separate viewport (e.g., for large amounts of streaming text).
  4. The user agent may satisfy the second success criteria by always rendering animated or blinking text as motionless, unblinking text.
Normative inclusions and exclusions
  1. This checkpoint does not apply for content the user agent cannot deterministically recognize as audio, video, animated images, or animated/blinking text.
  2. This configuration is required for content rendered without any user interaction (including content rendered on load or as the result of a script), as well as content rendered as the result of user interaction that is not an explicit user request (e.g., when the user activates a link).
  3. This checkpoint must be satisfied for all implemented audio, video, and animated image specifications; see the section on conformance profiles.
  4. When configured not to render audio, video, or animated images except on explicit user request, the user agent is not required to retrieve them until the user requests them explicitly.
  5. Checkpoint 4.3 addresses user control of blinking effects caused by rapid color changes.
  6. Conformance profile labels: VisualText, Animation, Video, Audio

Note: See guideline 4 for additional requirements related to the control of rendered audio, video, and animated images. When these content types are not rendered, they are considered conditional content. See checkpoint 2.3 for information about providing access to conditional content. Animation (a rendering effect) differs from streaming (a delivery mechanism). Streaming content might be rendered as an animation (e.g., an animated stock ticker or vertically scrolling text) or as static text (e.g., movie subtitles, which are rendered for a limited time, but do not give the impression of movement).

3.3 Toggle executable content (P1) Techniques for checkpoint 3.3
  1. Allow configuration not to execute any executable content (e.g., scripts, objects and applets).
Sufficient techniques
  1. Provide the user with the ability to toggle whether the base user agent executes content that it is able to . - if cond. content exists reveal it (2.3)
  2. Provide the user with the ability to toggle the loading of plugins that execute content the base browser is unable to execute - if cond. content exists reveal it (2.3)

Note: Executable content may provide very useful functionality, not all of which causes accessibility problems. If content is not executed it is important to instead render any conditional content that the author may provide.@@take another look at this@@

3.4 Toggle automatic content retrieval (P1) Techniques for checkpoint 3.4
  1. Allow configuration so that the user agent only retrieves content on explicit user request.
Normative inclusions and exclusions
  1. When the user chooses not to retrieve (fresh) content, the user agent may ignore that content; buffering is not required.
  2. This checkpoint only applies when the user agent (not the server) automatically initiates the request for fresh content. However, the user agent is not required to satisfy this checkpoint for "client-side redirects," i.e., author-specified instructions that a piece of content is temporary and intermediate, and is replaced by content that results from a second request.

Note: For example, if the user agent supports automatic content retrieval, to ensure that the user does not become disoriented by sudden automatic changes, allow configurations such as "Never retrieve content automatically" and "Require confirmation before content retrieval."

3.5 Toggle images (P2) Techniques for checkpoint 3.5
  1. Allow configuration not to render image content.
Sufficient techniques
  1. The user agent may satisfy this checkpoint by making images invisible, but this technique is not recommended.
Normative inclusions and exclusions
  1. This checkpoint must be satisfied for all implemented image specifications; see the section on conformance profiles.
  2. When configured not to render images, the user agent is not required to retrieve them until the user requests them explicitly.
  3. Conformance profile labels: Image

Note: When images are not rendered, they are considered conditional content. See checkpoint 2.3 for information about providing access to conditional content.

Guideline 4. Ensure user control of rendering

Checkpoints: 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.11, 4.12, 4.13, 4.14

Ensure that the user can select preferred styles (e.g., colors, size of rendered text, and synthesized speech characteristics) from choices offered by the user agent. Allow the user to override author-specified styles and user agent default styles.

Providing access to content (see guideline 2) includes enabling users to configure and control its rendering. Users with low vision may require that text be rendered at a size larger than the size specified by the author or by the user agent's default rendering. Users with color blindness may need to impose or prevent certain color combinations.

For dynamic presentations such as synchronized multimedia presentations created with SMIL 1.0 [SMIL], users with cognitive, hearing, visual, and physical disabilities may not be able to interact with a presentation within the time frame assumed by the author. To make the presentation accessible to these users, user agents rendering multimedia content (audio, video, and other animations), have to allow the user to control the playback rate of this content, and also to stop, start, pause, and navigate it quickly. User agents rendering audio have to allow the user to control the audio volume globally and to allow the user to control distinguishable audio tracks.

User agents with speech synthesis capabilities need to allow users to control various synthesized speech rendering parameters. For instance, some users may not be able to make use of high or low frequencies; these users have to be able to configure their speech synthesizers to use suitable frequencies.

Checkpoint definitions for visually rendered text

4.1 Configure text scale (P1) Techniques for checkpoint 4.1
  1. Allow global configuration of the scale of visually rendered text content. Preserve distinctions in the size of rendered text as the user increases or decreases the scale.
  2. As part of satisfying provision one of this checkpoint, provide a configuration option to override rendered text sizes specified by the author or user agent defaults.
  3. As part of satisfying provision one of this checkpoint, offer a range of text sizes to the user that includes at least:
Sufficient techniques
  1. The user agent may satisfy provision one of this checkpoint through a number of mechanisms, including zoom, magnification, and allowing the user to configure a reference size for rendered text (e.g., render text at 36 points unless otherwise specified). For example, for CSS2 [CSS2] user agents, the medium value of the font-size property corresponds to a reference size.
Normative inclusions and exclusions
  1. The word "scale" is used in this checkpoint to mean the general size of text.
  2. The user agent is not required to satisfy this requirement through proportional scaling. What must hold is that if rendered text A is smaller than rendered text B at one value of the configuration setting of provision one, then text A will still be smaller than text B at another value of this configuration setting.
  3. Conformance profile labels: VisualText
4.2 Configure font family (P1) Techniques for checkpoint 4.2
  1. Allow global configuration of the font family of all visually rendered text content.
  2. As part of satisfying provision one of this checkpoint, provide a configuration option to override font families specified by the author or by user agent defaults.
  3. As part of satisfying provision one of this checkpoint, offer a range of font families to the user that includes at least:
Sufficient techniques
  1. For text that cannot be rendered properly using the user's preferred font family, the user agent should substitute an alternative font family.
Normative inclusions and exclusions
  1. Conformance profile labels: VisualText

Note: For example, allow the user to specify that all text is to be rendered in a particular sans-serif font family.

4.3 Configure text colors (P1) Techniques for checkpoint 4.3
  1. Allow global configuration of the foreground and background color of all visually rendered text content.
  2. As part of satisfying provision one of this checkpoint, provide a configuration option to override foreground and background colors specified by the author or user agent defaults.
  3. As part of satisfying provision one of this checkpoint, offer a range of colors to the user that includes at least:
Normative inclusions and exclusions
  1. Color includes black, white, and grays.
  2. Conformance profile labels: VisualText

Note: User configuration of foreground and background colors may inadvertently lead to the inability to distinguish ordinary text from selected text or focused text. See checkpoint 10.2 for more information about highlight styles.

Checkpoint definitions for multimedia presentations and other presentations that change continuously over time

4.4 Slow multimedia (P1) Techniques for checkpoint 4.4
  1. Allow the user to slow the presentation rate of rendered audio and animation content (including video and animated images).
  2. As part of satisfying provision one of this checkpoint, for a visual track, provide at least one setting between 40% and 60% of the original speed.
  3. As part of satisfying provision one of this checkpoint, for a prerecorded audio track including audio-only presentations, provide at least one setting between 75% and 80% of the original speed.
  4. When the user agent allows the user to slow the visual track of a synchronized multimedia presentation to between 100% and 80% of its original speed, synchronize the visual and audio tracks (per checkpoint 2.6). Below 80%, the user agent is not required to render the audio track.
Normative inclusions and exclusions
  1. The user agent is not required to satisfy this checkpoint for audio and animations whose recognized role is to create a purely stylistic effect. Purely stylistic effects include background sounds, decorative animated images, and effects caused by style sheets.
  2. Conformance profile labels: Animation, Audio

Note: The style exception of this checkpoint is based on the assumption that authors have satisfied the requirements of the "Web Content Accessibility Guidelines 2.0" [WCAG20] not to convey information through style alone (e.g., through color alone or style sheets alone). @@RE-LOOK AT THIS NOTE@@

4.5 Start, stop, pause, and navigate multimedia (P1) Techniques for checkpoint 4.5
  1. Allow the user to stop, pause, and resume rendered audio and animation content (including video and animated images) that last three or more seconds at their default playback rate.
  2. Allow the user to navigate efficiently within rendered audio and animations (including video and animated images) that last three or more seconds at their default playback rate.
Sufficient techniques
  1. The user agent may satisfy the navigation requirement of provision two of this checkpoint through forward and backward serial access techniques (e.g., advance five seconds), or direct access techniques (e.g., start playing at the 10-minute mark), or some combination.
Normative inclusions and exclusions
  1. When using serial access techniques to satisfy provision two of this checkpoint, the user agent is not required to play back content during advance or rewind (though doing so may help orient the user).
  2. When the user pauses a real-time audio or animation, the user agent may discard packets that continue to arrive during the pause.
  3. This checkpoint applies to content that is either rendered automatically (e.g., on load) or on explicit request from the user.
  4. The user agent is not required to satisfy this checkpoint for audio and animations whose recognized role is to create a purely stylistic effect; see checkpoint 4.4 for more information about what constitutes a stylistic effect.
  5. Conformance profile labels: Animation, Audio

Note: The lower bound of three seconds is part of this checkpoint since control is not required for brief audio and animation content, such as short clips or beeps. Respect synchronization cues per checkpoint 2.6.

4.6 Do not obscure captions (P1) Techniques for checkpoint 4.6
  1. For graphical viewports, allow configuration so that captions synchronized with a visual track in content are not obscured by it.
Sufficient techniques
  1. Render captions "on top" of the visual track and, as part of satisfying checkpoint 4.3, allow the user to configure the foreground and background color of the rendered captions text.
  2. Render captions and video in separate viewports.

Checkpoint definitions for audio volume control

4.7 Global volume control (P1) Techniques for checkpoint 4.7
  1. Allow global configuration of the volume of all rendered audio.
  2. As part of satisfying provision one of this checkpoint, allow the user to choose zero volume (i.e., silent).
Normative inclusions and exclusions
  1. This checkpoint must be satisfied for all implemented specifications that produce sound; see the section on conformance profiles.
  2. Conformance profile labels: Audio
  3. Conformance detail: For both content and user agent

Note: User agents should allow configuration of volume through available operating environment mechanisms.

4.8 Independent volume control (P1) Techniques for checkpoint 4.8
  1. Allow independent control of the volumes of rendered audio content synchronized to play simultaneously.
Normative inclusions and exclusions
  1. The user control required by this checkpoint includes the ability to override author-specified volumes for the relevant sources of audio.
  2. The user agent is not required to satisfy this checkpoint for audio whose recognized role is to create a purely stylistic effect; see checkpoint 4.4 for more information about what constitutes a stylistic effect.
  3. Conformance profile labels: Audio

Note: The user agent should satisfy this checkpoint by allowing the user to control independently the volumes of all audio sources (e.g., by implementing a general audio mixer type of functionality). See checkpoint 4.10 for information about controlling the volume of synthesized speech.

Checkpoint definitions for synthesized speech rendering

4.9 Configure synthesized speech rate (P1) Techniques for checkpoint 4.9
  1. Allow configuration of the synthesized speech rate, according to the full range offered by the speech synthesizer.
Normative inclusions and exclusions
  1. Conformance profile labels: Speech

Note: The range of synthesized speech rates offered by the speech synthesizer may depend on natural language.

4.10 Configure synthesized speech volume (P1) Techniques for checkpoint 4.10
  1. Allow control of the synthesized speech volume, independent of other sources of audio.
Normative inclusions and exclusions
  1. The user control required by this checkpoint includes the ability to override author-specified synthesized speech volume.
  2. Conformance profile labels: Speech

Note: See checkpoint 4.8 for information about independent volume control of different sources of audio.

4.11 Configure synthesized speech characteristics (P1) Techniques for checkpoint 4.11
  1. Allow configuration of synthesized speech characteristics according to the full range of values offered by the speech synthesizer.
Normative inclusions and exclusions
  1. Conformance profile labels: Speech

Note: Some speech synthesizers allow users to choose values for synthesized speech characteristics at a higher abstraction layer, i.e., by choosing from present options that group several characteristics. Some typical options one might encounter include: voice (e.g., adult male voice, female child voice, robot voice), pitch, and stress. Ranges for values may vary among speech synthesizers.

4.12 Specific synthesized speech characteristics (P2) Techniques for checkpoint 4.12
  1. Allow configuration of synthesized speech pitch. Pitch refers to the average frequency of the speaking voice.
  2. Allow configuration of synthesized speech pitch range. Pitch range specifies a variation in average frequency.
  3. Allow configuration of synthesized speech stress. Stress refers to the height of "local peaks" in the intonation contour of the voice.
  4. Allow configuration of synthesized speech richness. Richness refers to the richness or brightness of the voice.
Normative inclusions and exclusions
  1. Conformance profile labels: Speech

Note: This checkpoint is more specific than checkpoint 4.11. It requires support for the voice characteristics listed in the provisions of this checkpoint. Definitions for these characteristics are based on descriptions in section 19 of the Cascading Style Sheets Level 2 Recommendation [CSS2]; refer to that specification for additional informative descriptions. Some speech synthesizers allow users to choose values for synthesized speech characteristics at a higher abstraction layer, for example, by choosing from present options distinguished by gender, age, or accent. Ranges of values may vary among speech synthesizers.

4.13 Configure synthesized speech features (P2) Techniques for checkpoint 4.13
  1. Provide support for user-defined extensions to the synthesized speech dictionary.
  2. Provide support for spell-out: where text is spelled one character at a time, or according to language-dependent pronunciation rules.
  3. Allow at least two configurations for speaking numerals: one where numerals are spoken as individual digits, and one where full numbers are spoken.
  4. Allow at least two configurations for speaking punctuation: one where punctuation is spoken literally, and one where punctuation is rendered as natural pauses.
Normative inclusions and exclusions
  1. Conformance profile labels: Speech

Note: Definitions for the functionalities listed in the provisions of this checkpoint are based on descriptions in section 19 of the Cascading Style Sheets Level 2 Recommendation [CSS2]; refer to that specification for additional informative descriptions.

Checkpoint definitions related to style sheets

4.14 Choose style sheets (P1) Techniques for checkpoint 4.14
  1. Allow the user to choose from and apply alternative author style sheets (such as linked style sheets).
  2. Allow the user to choose from and apply at least one user style sheet.
  3. Allow the user to turn off (i.e., ignore) author and user style sheets.
Normative inclusions and exclusions
  1. This checkpoint only applies to user agents that support style sheets.

Note: By definition, the user agent's default style sheet is always present, but may be overridden by author or user styles. Developers should not consider that the user's ability to turn off author and user style sheets is an effective way to improve content accessibility; turning off style sheet support means losing the many benefits they offer. Instead, developers should provide users with finer control over user agent or content behavior known to raise accessibility barriers. The user should only have to turn off author and user style sheets as a last resort.

Guideline 5. Ensure user control of user interface behavior

Checkpoints: 5.1, 5.2, 5.3, 5.4, 5.5

Ensure that the user can control the behavior of viewports and user interface controls, including those that may be manipulated by the author (e.g., through scripts).

Control of viewport behavior is important to accessibility. Unexpected changes to the point of regard — what the user is presumed to be viewing — may cause users to lose track of how many viewports are open, or which viewport has the current focus. If carried out automatically, these changes might go unnoticed (e.g., by some users with blindness) or be disorienting (e.g., to some users with a cognitive disability). This guideline includes requirements for control of opening and closing viewports, the relative position of graphical viewports, changes to focus, and inadvertent form submissions.

Checkpoint definitions

Guideline: 5.X Manage viewport opening and focus

Level A Success Criteria for Guideline 5.X
Level AA Success Criteria for Guideline 5.X
Level AAA Success Criteria for Guideline 5.X
5.1 No automatic content focus change (P2) Techniques for checkpoint 5.1
  1. Allow configuration so that if a viewport opens without explicit user request, neither its content focus nor its user interface focus automatically becomes the current focus.
Sufficient techniques
  1. To satisfy provision one of this checkpoint, configuration is preferred, but is not required if the content focus can only ever be moved on explicit user request.
5.2 Keep viewport on top (P2) Techniques for checkpoint 5.2
  1. For graphical user interfaces, allow configuration so that the viewport with the current focus remains "on top" of all other viewports with which it overlaps.
5.3 Manual viewport open only (P2) Techniques for checkpoint 5.3
  1. Allow configuration so that viewports only open on explicit user request.
  2. When configured per provision one of this checkpoint, instead of opening a viewport automatically, alert the user and allow the user to open it with an explicit request (e.g., by confirming a prompt or following a link generated by the user agent).
  3. Allow the user to close viewports.
Sufficient techniques
  1. To satisfy provision one of this checkpoint, configuration is preferred, but is not required if viewports can only ever open on explicit user request.
Normative inclusions and exclusions
  1. If a viewport (e.g., a frame set) contains other viewports, the provisions of this checkpoint only apply to the outermost container viewport.
  2. User creation of a new viewport (e.g., empty or with a new resource loaded) through the user agent's user interface constitutes an explicit user request.

Note: Generally, viewports open automatically as the result of instructions in content. See also checkpoint 5.1 (for control over changes of focus when a viewport opens) and checkpoint 6.6 (for programmatic notification of changes to the user interface).

5.4 Selection and focus in viewport (P2) Techniques for checkpoint 5.4
  1. Ensure that when a viewport's selection or content focus changes, it is at least partially in the viewport after the change.
Normative inclusions and exclusions
  1. Conformance profile labels: Selection

Note: For example, if users navigating links move to a portion of the document outside a graphical viewport, the viewport should scroll to include the new location of the focus. Or, for users of audio viewports, allow configuration to render the selection or focus immediately after the change.

5.5 Confirm form submission (P2) Techniques for checkpoint 5.5
  1. Allow configuration to prompt the user to confirm (or cancel) any form submission.
Sufficient techniques
  1. Configuration is preferred, but is not required if forms can only ever be submitted on explicit user request.

Note: Examples of automatic form submission include: script-driven submission when the user changes the state of a particular form control (e.g., via the pointing device), submission when the user has interacted with all form controls, and submission when an onmouseover or onchange event occurs.

Guideline 6. Implement interoperable application programming interfaces

Checkpoints: 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, 6.10

Implement interoperable interfaces to communicate with other software (e.g., assistive technologies, the operating environment, and plug-ins).

This guideline addresses interoperability between a conforming user agent and other software, in particular assistive technologies. The checkpoints of this guideline require implementation of application programming interfaces (APIs) for communication. There are three types of requirements in this guideline:

  1. Requirements for what information must be communicated through an API
  2. Requirements for which APIs or types of APIs must be used to communicate this information
  3. Requirements for additional characteristics of these APIs

Note: The User Agent Accessibility Guidelines Working Group believes that, in order to promote interoperability between a conforming user agent and more than one assistive technology, it is more important to implement conventional APIs than custom APIs, even though custom APIs may offer specialized access.

Checkpoint definitions

6.1 Programmatic access to HTML/XML infoset (P1) Techniques for checkpoint 6.1
  1. Provide programmatic read access to XML content by making available all of the information items defined by the W3C XML Infoset [INFOSET].
  2. Provide programmatic read access to HTML content by making available all of the following information items defined by the W3C XML Infoset [INFOSET]:
  3. If the user can modify the state or value of a piece of HTML or XML content through the user interface (e.g., by checking a box or editing a text area), allow programmatic read access to the current state or value, and allow the same degree of write access programmatically as is available through the user interface.
6.2 DOM access to HTML/XML content (P1) Techniques for checkpoint 6.2
  1. Provide access to the content required in checkpoint 6.1 by conforming to the following modules of the W3C Document Object Model (DOM) Level 2 Core Specification [DOM2CORE] and exporting bindings for the interfaces they define:
  2. As part of satisfying provision one of this checkpoint:
Normative inclusions and exclusions
  1. Refer to the "Document Object Model (DOM) Level 2 Core Specification" [DOM2CORE] for information about which versions of HTML, XML, Java, and ECMAScript are covered. Appendix D contains the Java bindings and Appendix E contains the ECMAScript bindings.
  2. The user agent is not required to export the bindings outside of the user agent process (though doing so may be useful to assistive technology developers).

Note: This checkpoint stands apart from checkpoint 6.1 to emphasize the distinction between what information is required and how to provide access to that information. Furthermore, the DOM Level 2 Core Specification does not provide access to current states and values referred to in provision three of checkpoint 6.1. For HTML content, the interfaces defined in [DOM2HTML] do provide access to current states and values.

6.3 Programmatic access to non-HTML/XML content (P1) Techniques for checkpoint 6.3
  1. For content other than HTML and XML, provide structured programmatic read access to content.
  2. If the user can modify the state or value of a piece of non-HTML/XML content through the user interface (e.g., by checking a box or editing a text area), allow programmatic read access to the current state or value, and allow the same degree of write access programmatically as is available through the user interface.
  3. As part of satisfying provision one of this checkpoint, implement at least one API according to this API cascade:
Normative inclusions and exclusions
  1. "Structured programmatic access" means access through an API to recognized information items of the content (such as the information items of the XML Infoset [INFOSET]). Plain text has little structure, so an API that provides access to it will be correspondingly less complex than an API for XML content. For content more structured than plain text, an API that only provides access to a stream of characters does not satisfy the requirement of providing structured programmatic access. This document does not otherwise define what is sufficiently structured access.
  2. An API is considered "available" if the specification of the API is published (e.g., as a W3C Recommendation) in time for integration into a user agent's development cycle.

Note: This checkpoint addresses content not covered by checkpoints 6.1 and 6.2.

6.4 Programmatic access to information about rendered content (P1) Techniques for checkpoint 6.4
  1. For graphical user agents, make available bounding dimensions and coordinates of rendered graphical objects. Coordinates must be relative to the point of origin in the graphical environment (e.g., with respect to the desktop), not the viewport.
  2. For graphical user agents, provide access to the following information about each piece of rendered text: font family, font size, and foreground and background colors.
  3. As part of satisfying provisions one and two of this checkpoint, implement at least one API according to the API cascade described in provision two of checkpoint 6.3.

Note: User agents should provide programmatic access to additional useful information about rendered content that is not available through the APIs required by checkpoints 6.2 and 6.3, including the correspondence (in both directions) between graphical objects and their source in the document object, and information about the role of each graphical object.

6.5 Programmatic operation of user agent user interface (P1) Techniques for checkpoint 6.5
  1. Provide programmatic read access to user agent user interface controls, selection, content focus, and user interface focus.
  2. If the user can modify the state or value of a user agent user interface control (e.g., by checking a box or editing a text area), allow programmatic read access to the current state or value, and allow the same degree of write access programmatically as is available through the user interface.
  3. As part of satisfying provisions one and two of this checkpoint, implement at least one API according to the API cascade described in provision two of checkpoint 6.3.
Normative inclusions and exclusions
  1. For security reasons, user agents are not required to allow instructions in content to modify user agent user interface controls. See more information on security considerations.
  2. Conformance detail: For user agent features

Note: APIs used to satisfy the requirements of this checkpoint may vary. For instance, they may be independent of a particular operating environment (e.g., the W3C DOM), or the conventional APIs for a particular operating environment, or the conventional APIs for programming languages, plug-ins, or virtual machine environments. User agent developers are encouraged to implement APIs that allow assistive technologies to interoperate with multiple types of software in a given operating environment (e.g., user agents, word processors, and spreadsheet programs), as this reuse will benefit users and assistive technology developers. User agents should always follow operating environment conventions for the use of input and output APIs.

6.6 Programmatic notification of changes (P1) Techniques for checkpoint 6.6
  1. Provide programmatic notification of changes to content, states and values of content, user agent user interface controls, selection, content focus, and user interface focus.
  2. As part of satisfying provision one of this checkpoint, implement at least one API according to the API cascade of provision two of checkpoint 6.3.
Normative inclusions and exclusions
  1. The user agent is not required to provide notification of changes in the rendering of content (e.g., due to an animation effect or an effect caused by a style sheet) unless the document object is modified as part of those changes.
  2. Conformance profile labels: Selection
  3. Conformance detail: For both content and user agent

Note: For instance, provide programmatic notification when user interaction in one frame causes automatic changes to content in another.

6.7 Conventional keyboard APIs (P1) Techniques for checkpoint 6.7
  1. Implement APIs for the keyboard (@@better defn needed@@) as follows:

Note: An operating environment may define more than one conventional API for the keyboard. For instance, for Japanese and Chinese, input may be processed in two stages, with an API for each stage.

6.8 API character encodings (P1) Techniques for checkpoint 6.8
  1. For an API implemented to satisfy requirements of this document, support the character encodings required for that API.
Normative inclusions and exclusions
  1. Conformance detail: For both content and user agent

Note: Support for character encodings is an important part of ensuring that text is correctly communicated to assistive technologies. For example, the DOM Level 2 Core Specification [DOM2CORE], section 1.1.5 requires that the DOMString type be encoded using UTF-16.

6.9 DOM access to CSS style sheets (P2) Techniques for checkpoint 6.9
  1. For user agents that implement Cascading Style Sheets (CSS), provide programmatic access to style sheets by conforming to the CSS module of the W3C Document Object Model (DOM) Level 2 Style Specification [DOM2STYLE] and exporting bindings for the interfaces it defines.
  2. As part of satisfying provision one of this checkpoint:
Normative inclusions and exclusions
  1. For the purposes of satisfying this checkpoint, Cascading Style Sheets (CSS) are defined by either CSS Level 1 [CSS1] or CSS Level 2 [CSS2].
  2. Refer to the "Document Object Model (DOM) Level 2 Style Specification" [DOM2STYLE] for information about which versions of Java and ECMAScript are covered. Appendix B contains the Java bindings and Appendix C contains the ECMAScript bindings.
  3. The user agent is not required to export the bindings outside of the user agent process.
6.10 Timely exchanges through APIs (P2) Techniques for checkpoint 6.10
  1. For APIs implemented to satisfy the requirements of this document, ensure that programmatic exchanges proceed in a timely manner.
Normative inclusions and exclusions
  1. Conformance detail: For both content and user agent

Note: For example, the programmatic exchange of information required by other checkpoints in this document should be efficient enough to prevent information loss, a risk when changes to content or user interface occur more quickly than the communication of those changes. Timely exchange is also important for the proper synchronization of alternative renderings. The techniques for this checkpoint explain how developers can reduce communication delays. This will help ensure that assistive technologies have timely access to the document object model and other information that is important for providing access.

Guideline 7. Observe operating environment conventions

Checkpoints: 7.1, 7.2, 7.3, 7.4

Observe operating environment conventions for the user agent user interface, documentation, input configurations, and installation.

Part of user agent accessibility involves following the conventions of the user's operating environment, including:

Following operating environment conventions also increases predictability for users and for developers of assistive technologies. These guidelines explain what users will expect from the look and feel of the user interface, keyboard conventions, and documentation. These guidelines also include information about accessibility features that the user agent should adopt rather than reimplement.

The chapter on conformance explains more on the use of operating environment features as part of conformance.

Checkpoint definitions

7.X Observe operating environment conventions

Level A Success Criteria for Guideline 7.X
Level AA Success Criteria for Guideline 7.X
Level AAA Success Criteria for Guideline 7.X

 

7.1 Respect focus and selection conventions (P1) Techniques for checkpoint 7.1
  1. Follow operating environment conventions that benefit accessibility when implementing the selection, content focus, and user interface focus.
Normative inclusions and exclusions
  1. This checkpoint is mutually exclusive of checkpoint 7.3 since it has a higher priority.
  2. Conformance profile labels: Selection

Note: See checkpoints 9.1 and 9.2 for more information about content focus and user interface focus.

7.2 Respect input configuration conventions (P1) Techniques for checkpoint 7.2
  1. Ensure that default input configurations of the user agent do not interfere with operating environment accessibility conventions (e.g., for keyboard accessibility, speech commands).
Normative inclusions and exclusions
  1. Conformance detail: For user agent features

Note: Information about operating environment accessibility conventions is available in the Techniques document [UAAG10-TECHS]. See checkpoint 11.5 for information about the user agent's default input configuration.

7.3 Respect operating environment conventions (P2) Techniques for checkpoint 7.3
  1. Follow operating environment conventions that benefit accessibility. In particular, follow conventions that benefit accessibility for user interface design, keyboard configuration, product installation, and documentation.
Normative inclusions and exclusions
  1. For the purposes of this checkpoint, an operating environment convention that benefits accessibility is either
    • one identified as such in operating environment design or accessibility guidelines, or
    • one that allows the author to satisfy any requirement of the "Web Content Accessibility Guidelines 2.0" [WCAG20] or of the current document.
  2. This checkpoint excludes the requirements of checkpoints 7.1 and 7.4.
  3. Conformance detail: For user agent features

Note: Some of these conventions (e.g., sticky keys, mouse keys, and show sounds) are discussed in the Techniques document [UAAG10-TECHS].

7.4 Provide input configuration indications (P2) Techniques for checkpoint 7.4
  1. Follow operating environment conventions to indicate the input configuration.
Normative inclusions and exclusions
  1. This checkpoint is mutually exclusive of checkpoint 7.3 to emphasize the importance of consistency in input configurations.
  2. Conformance detail: For user agent features

Note: For example, in some operating environments, when a functionality may be triggered through a menu and through the keyboard, the developer may design the menu entry so that the character of the activating key is also shown. See checkpoint 11.5 for information about the user agent's default input configuration.

Guideline 8. Implement specifications that benefit accessibility

Checkpoints: 8.1, 8.2

Support the accessibility features of all implemented specifications. Implement W3C Recommendations when available and appropriate for a task.

Developers should implement open specifications. Conformance to open specifications benefits interoperability and accessibility by making it easier to design assistive technologies (also discussed in guideline 6).

While developers should implement the accessibility features of any specification (checkpoint 8.1), this document recommends conformance to W3C Recommendations in particular (checkpoint 8.2) for several reasons:

Checkpoint definitions

8.1 Implement accessibility features (P1) Techniques for checkpoint 8.1
  1. Implement the accessibility features of specifications (e.g., markup languages, style sheet languages, metadata languages, and graphics formats).
Normative inclusions and exclusions
  1. This checkpoint applies to both W3C-developed and non-W3C specifications.
  2. For the purposes of this checkpoint, an accessibility feature of a specification is either:
    • one identified as such in the specification, or
    • one that allows the author to satisfy any requirement of the "Web Content Accessibility Guidelines 2.0" [WCAG20].
  3. The user agent is not required to satisfy this checkpoint for all implemented specifications; see the section on conformance profiles for more information.
  4. Conformance detail: For all content

Note: The Techniques document [UAAG10-TECHS] provides information about the accessibility features of some specifications, including W3C specifications.

8.2 Conform to specifications (P2) Techniques for checkpoint 8.2
  1. Use and conform to either
Sufficient techniques
  1. When a requirement of another specification contradicts a requirement of the current document, the user agent may disregard the requirement of the other specification and still satisfy this checkpoint.
Normative inclusions and exclusions
  1. A specification is considered "available" if it is published (e.g., as a W3C Recommendation) in time for integration into a user agent's development cycle.
  2. The user agent is not required to satisfy this checkpoint for all implemented specifications; see the section on conformance profiles for more information.
  3. Conformance detail: For all content

Note: For instance, for markup, the user agent may conform to HTML 4 [HTML4], XHTML 1.0 [XHTML10], and/or XML 1.0 [XML]. For style sheets, the user agent may conform to CSS ([CSS1], [CSS2]). For mathematics, the user agent may conform to MathML 2.0 [MATHML20]. For synchronized multimedia, the user agent may conform to SMIL 1.0 [SMIL].

Guideline 9. Provide navigation mechanisms

Checkpoints: 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 9.10

Provide access to content through a variety of navigation mechanisms, including sequential navigation, direct navigation, searches, and structured navigation.

Users should be able to navigate to important pieces of content within a configurable view, identify the type of object they have navigated to, interact with that object easily (if it is an enabled element), and review the surrounding context (to orient themselves). Providing a variety of navigation and search mechanisms helps users with disabilities (and all users) access content more efficiently. Navigation and searching are particularly important to users with serial access to content or who navigate sequentially (by moving the focus).

Direct navigation (e.g., to a particular link or paragraph) is faster than sequential navigation, but generally requires familiarity with the content. Direct navigation is important to users with some physical disabilities (who may have little or no manual dexterity and/or increased tendency to push unwanted buttons or keys) and to users with visual disabilities. Expert users also benefit from direct navigation. Direct navigation may be possible with the pointing device or the keyboard (e.g., keyboard shortcuts).

Structured navigation mechanisms offer both context and speed. User agents should allow users to navigate to content known to be structurally important, such as blocks of content, headers and sections, tables, forms and form elements, enabled elements, navigation mechanisms, and containers. For information about programmatic access to document structure, see guideline 6.

User agents should allow users to configure navigation mechanisms (e.g., to allow navigation of links only, or links and headings, or tables and forms).

Checkpoint definitions

9.X Focus Management

Level A Success Criteria for Guideline 9.X
Level AA Success Criteria for Guideline 9.X
Level AAA Success Criteria for Guideline 9.X
9.1 Provide content focus (P1) Techniques for checkpoint 9.1
  1. Provide at least one content focus for each viewport (including frames) where enabled elements are part of the rendered content.
  2. Allow the user to make the content focus of each viewport the current focus.
Normative inclusions and exclusions
  1. When a viewport includes no enabled elements (either because the format does not provide for this, or a given piece of content has no enabled elements), the content focus requirements of the following checkpoints do not apply: 1.2, 5.1, 5.4, 6.6, 7.1, 9.3, 9.4, 9.5, 9.6, 9.7, 10.2, and 11.5.

Note: For example, when two frames of a frameset contain enabled elements, allow the user to make the content focus of either frame the current focus. Note that viewports "owned" by plug-ins that are part of a conformance claim are also covered by this checkpoint. See checkpoint 7.1 for information about implementing content focus according to operating environment conventions.

9.2 Provide user interface focus (P1) Techniques for checkpoint 9.2
  1. Provide a user interface focus.

Note: See checkpoint 7.1 for information about implementing user interface focus according to operating environment conventions.

9.3 Move content focus (P1) Techniques for checkpoint 9.3
  1. Allow the user to move the content focus to any enabled element in the viewport.
  2. Allow configuration so that the content focus of a viewport only changes on explicit user request.
  3. If the author has not specified a navigation order, allow at least forward sequential navigation, in document order, to each element in the set established by provision one of this checkpoint.
Sufficient techniques
  1. To satisfy provision two of this checkpoint, configuration is preferred, but is not required if the content focus only ever changes on explicit user request.
Normative inclusions and exclusions
  1. The user agent may also include disabled elements in the navigation order.

Note: In addition to forward sequential navigation, the user agent should also allow reverse sequential navigation. See checkpoint 9.9 for information about structured navigation. See checkpoints 5.1 and 6.6 for more information about focus changes.

9.4 Restore viewport state history (P1) Techniques for checkpoint 9.4
  1. If the user agent maintains a viewport history mechanism (e.g., via the "back button") that stores previous "viable" states (i.e., that have not been negated by the content, user agent settings or user agent extensions) it must maintain information about the point of regard and it must restore the saved values when the user returns to a state in the history.
Normative inclusions and exclusions
  1. The viewport history associates values for these three state variables (point of regard, content focus, and selection) with a particular document object. If the user returns to a state in the history and the user agent retrieves new content, the user agent is not required to restore the saved values of the three state variables.
  2. Conformance profile labels: Selection
9.5 No events on focus change (P2) Techniques for checkpoint 9.5
  1. Allow configuration so that moving the content focus to or from an enabled element does not automatically activate any explicitly associated event handlers of any event type.
Normative inclusions and exclusions
  1. Conformance profile labels: Events

Note: For instance, in this configuration for an HTML document, do not activate any handlers for the onfocus, onblur, or onchange attributes. In this configuration, user agents should still apply any stylistic changes (e.g., highlighting) that may occur when there is a change in content focus.

9.6 Show event handlers (P2) Techniques for checkpoint 9.6
  1. For the element with content focus, make available the list of input device event types for which there are event handlers explicitly associated with the element.
Normative inclusions and exclusions
  1. Conformance profile labels: Events

Note: For example, allow the user to query the element with content focus for the list of input device event types, or add them directly to the sequential navigation order described in checkpoint 9.3. See checkpoint 1.2 for information about activation of event handlers associated with the element with focus.

9.7 Move content focus in reverse (P2) Techniques for checkpoint 9.7
  1. Extend the functionality required in provision three of checkpoint 9.3 by allowing the same sequential navigation in reverse document order.
  2. As part of satisfying provision one of this checkpoint, the user agent must not include disabled elements in the navigation order.
9.8 Provide text search (P2) Techniques for checkpoint 9.8
  1. Allow the user to search within rendered (e.g., not hidden with a style) content for text and text alternatives for a sequence of characters from the document character set.
  2. Allow the user to start a forward or backward search (in document order) from any selected or focused location in content.
  3. When there is a match, do both of the following:
  4. Alert the user when there is no match or after the last match in content (i.e., prior to starting the search over from the beginning of content).
  5. Provide a case-insensitive search option for text in scripts (i.e., writing systems) where case is significant.
Normative inclusions and exclusions
  1. Conformance detail: For all rendered content

Note: If the user has not indicated a start position for the search, the search should start from the beginning of content. Per checkpoint 7.3, use operating environment conventions for indicating the result of a search.

9.9 Allow structured navigation (P2) Techniques for checkpoint 9.9
  1. Provide efficient navigation over important structural elements in rendered content.
  2. As part of satisfying provision one of this checkpoint, allow forward and backward sequential navigation.

Note: This specification intentionally does not identify which "important elements" must be navigable as this will vary by specification. What constitutes "efficient navigation" may depend on a number of factors as well, including the "shape" of content (e.g., sequential navigation of long lists is not efficient) and desired granularity (e.g., among tables, then among the cells of a given table). Refer to the Techniques document [UAAG10-TECHS] for information about identifying and navigating important elements.

9.10 Configure important elements (P3) Techniques for checkpoint 9.10
  1. Allow configuration of the set of important elements and attributes identified for checkpoints 9.9 and 10.4.
  2. As part of satisfying provision one of this checkpoint, allow the user to include and exclude element types in the set.

Note: For example, allow the user to navigate only paragraphs, or only headings and paragraphs, or to suppress and restore navigation bars, or to navigate within and among tables and table cells.

Guideline 10. Orient the user

Checkpoints: 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7

Provide information that will help the user understand browsing context.

All users require clues to help them understand their "location" when browsing: where they are, how they got there, where they can go, and what's nearby. Some mechanisms that provide such clues through the user interface (visually, as audio, or as braille) include:

Orientation mechanisms such as these are especially important to users with serial access to content or who navigate sequentially. For instance, some users cannot scan a graphically displayed table with their eyes for information about a table cell's headers or neighboring cells. User agents need to provide other means for users to understand, for example, table cell relationships, frame relationships (what relationship does the graphical layout convey?), form context (have I filled out the form completely?), and link information (have I already visited this link?).

Checkpoint definitions

10.1 Associate table cells and headers (P1) Techniques for checkpoint 10.1
  1. For graphical user agents that render tables, for each table cell, allow the user to view associated header information.
Sufficient techniques
  1. The user agent may satisfy this checkpoint by allowing the user to query each table cell for associated header information.
  2. The user agent may satisfy this checkpoint by rendering the table cell and associated header information so they are both visible in the same viewport.
Normative inclusions and exclusions
  1. This checkpoint refers only to cell/header relationships that the user agent can recognize.
10.2 Highlight selection, content focus, enabled elements, visited links (P1) Techniques for checkpoint 10.2
  1. Allow global configuration to highlight the following four classes of information in each viewport: the selection, content focus, enabled elements, and recently visited links.
  2. For graphical user interfaces, as part of satisfying provision one of this checkpoint, allow at least one configuration where the highlight mechanisms for the four classes of information:
  3. For graphical user interfaces, as part of satisfying provision one of this checkpoint, if a highlight mechanism involves text size, font family, rendered text foreground and background colors, or text decorations, offer at least the following range of values:
  4. Highlight enabled elements according to the granularity specified in the format. For example, an HTML user agent rendering a PNG image as part of a client-side image map is only required to highlight the image as a whole, not each enabled region. An SVG user agent rendering an SVG image with embedded graphical links is required to highlight each (enabled) link that may be rendered independently according to the SVG specification.
Normative inclusions and exclusions
  1. Conformance profile labels: Selection

Note: Examples of highlight mechanisms for selection and content focus include foreground and background color variations, underlining, border styling, and distinctive synthesized speech prosody. Because the selection and focus change frequently, user agents should not highlight them using mechanisms (e.g., font size variations) that cause content to reflow, as this may disorient the user. Graphical highlight mechanisms that generally do not rely on rendered text foreground and background color alone include underlines or border styling. Per checkpoint 7.1, follow operating environment conventions that benefit accessibility when implementing the selection and content focus. For instance, if specified at the level of the operating environment, inherit the user's preferences for selection styles.

10.3 Single highlight configuration (P2) Techniques for checkpoint 10.3
  1. Extend the functionality required by provision two of checkpoint 10.2 by allowing configuration through a single setting.
Normative inclusions and exclusions
  1. Conformance profile labels: Selection
10.4 Provide outline view (P2) Techniques for checkpoint 10.4
  1. Make available to the user an "outline" view of rendered content, composed of labels for important structural elements (e.g., heading text, table titles, form titles, and other labels that are part of the content).
Normative inclusions and exclusions
  1. What constitutes a label is defined by each markup language specification. For example, in HTML, a heading (H1-H6) is a label for the section that follows it, a CAPTION is a label for a table, and the title attribute is a label for its element.
  2. The user agent is not required to generate a label for an important element when no label is present in content. The user agent may generate a label when one is not present.
  3. A label is not required to be text only.

Note: This outline view will provide the user with a simplified view of content (e.g, a table of contents). For information about what constitutes the set of important structural elements, see the Note following checkpoint 9.9. By making the outline view navigable, it is possible to satisfy this checkpoint and checkpoint 9.9 together: allow users to navigate among the important elements of the outline view, and to navigate from a position in the outline view to the corresponding position in a full view of content. See checkpoint 9.10 for additional configuration options.

10.5 Provide link information (P3) Techniques for checkpoint 10.5
  1. To help the user decide whether to traverse a link in content, make available the following information about it:
Normative inclusions and exclusions
  1. User agents are expected to compute information about recently traversed links. For the other link information of this checkpoint, the user agent is only required to make available what is present in content.
  2. The user agent is not required to compute or make available information that requires retrieval of linked Web resources.

Checkpoint definitions for the user interface

10.6 Highlight current viewport (P1) Techniques for checkpoint 10.6
  1. Highlight the viewport with the current focus (including any frame that takes current focus).
  2. For graphical viewports, as part of satisfying provision one of this checkpoint, provide at least one highlight mechanism that does not rely on rendered text foreground and background colors alone (e.g., use a thick outline).
  3. If the techniques used to satisfy provision one of this checkpoint involve rendered text size, font family, rendered text foreground and background colors, or text decorations, allow global configuration and offer same ranges of values required by provision three of checkpoint 10.2.

Note: See checkpoint 7.1 for information about implementing highlight mechanisms according to operating environment conventions.

10.7 Indicate viewport position (P3) Techniques for checkpoint 10.7
  1. Indicate the viewport's position relative to rendered content (e.g., the proportion of an audio or video clip that has been played, or the proportion of a Web page that has been viewed).
Sufficient techniques
  1. The user agent may calculate the relative position according to content focus position, selection position, or viewport position, depending on how the user has been browsing.
  2. The user agent may indicate the proportion of content viewed in a number of ways, including as a percentage or as a relative size in bytes. See checkpoint 1.3 for more information about text versions of messages to the user, including messages about position information.
Normative inclusions and exclusions
  1. For two-dimensional spatial renderings, relative position includes both vertical and horizontal positions.
  2. This checkpoint does not require the user agent to present information about retrieval progress. However, for streaming content, viewport position may be closely tied to retrieval progress.

Guideline 11. Allow configuration and customization

Checkpoints: 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7

Allow users to configure the user agent so that frequently performed tasks are made convenient, and allow users to save their preferences.

Web users have a wide range of capabilities and need to be able to configure the user agent according to their preferences for styles, graphical user interface configuration, and keyboard configuration. Most of the checkpoints in this guideline pertain to the input configuration: how user agent behavior is controlled through keyboard input, pointing device input, and voice input. An input configuration is the set of "bindings" between user agent functionalities and user interface input mechanisms.

The chapter on conformance explains more about configuration requirements and conformance.

Checkpoint definitions

11.1 Current user input configuration (P1) Techniques for checkpoint 11.1
  1. Provide information to the user about current user preferences for input configurations.
Sufficient techniques
  1. To satisfy this checkpoint, the user agent may make available binding information in a centralized fashion (e.g., a list of bindings) or a distributed fashion (e.g., by listing keyboard shortcuts in user interface menus). See related documentation checkpoints 12.2, 12.3, and 12.5.
Normative inclusions and exclusions
  1. Conformance detail: For user agent features
11.2 Current author input configuration (P2) Techniques for checkpoint 11.2
  1. Provide a centralized view of the current author-specified input configuration.
Sufficient techniques
  1. The user agent may satisfy this checkpoint by providing different views for different input modalities (keyboard, pointing device, and voice).
Normative inclusions and exclusions
  1. Conformance detail: For all content

Note: For example, for HTML documents, provide a view of keyboard bindings specified by the author through the accesskey attribute. The intent of this checkpoint is to centralize information about author-specified bindings so that the user does not have to read an entire document to learn about available bindings.

11.3 Allow override of bindings (P2) Techniques for checkpoint 11.3
  1. Allow the user to override any binding that is part of the user agent default input configuration.
Normative inclusions and exclusions
  1. The user agent is not required to allow the user to override conventional bindings for the operating environment (e.g., for access to help).
  2. The override requirement only applies to bindings for the same input modality (e.g., the user must be able to override a keyboard binding with another keyboard binding).
  3. This checkpoint excludes the requirements of checkpoint 11.4.
  4. Conformance detail: For user agent features

Note: See checkpoint 11.5 for default input configuration requirements and checkpoint 12.3 for information about their documentation.

11.4 Single-key access (P2) Techniques for checkpoint 11.4
  1. Allow the user to override any binding in the user agent default keyboard configuration with a binding to either a key plus modifier keys or to a single key.
  2. For each functionality in the set required by checkpoint 11.5, allow the user to configure a single-key binding. A single-key binding is one where a single key press performs the task, with zero modifier keys.
Sufficient techniques
  1. The user agent may satisfy the requirements of provision two of this checkpoint with a "single-key mode." In a single-key mode, the complete set of functionalities required by provision two must be available through single-key bindings. The user must be able to remain in single-key mode until explicitly requesting to leave it.
Normative inclusions and exclusions
  1. In this checkpoint, "key" refers to a physical key of the keyboard (rather than, say, a character of the document character set).
  2. The user agent is not required to allow the user to override conventional bindings for the operating environment (e.g., for access to help).
  3. Provision two of this checkpoint does not require single physical key bindings for character input, only for the activation of user agent functionalities.
  4. If the number of physical keys on the keyboard is less than the number of functionalities required by checkpoint 11.5, then provision two of this checkpoint does not require the user agent to allow single-key bindings for all of the functionalities. The user agent should give preference to those functionalities listed in provision one of checkpoint 11.5.
  5. This checkpoint is mutually exclusive of checkpoint 11.3 since it is specific to the keyboard and to emphasize the importance of easy keyboard access.
  6. Conformance detail: For user agent features

Note: Because single-key access is so important to some users with physical disabilities, user agents should ensure that: (1) most keys of the physical keyboard may be configured for single-key bindings, and (2) most functionalities of the user agent may be configured for single-key bindings. For information about access to user agent functionality through a keyboard API, see checkpoint 6.7.

11.5 Default input configuration (P2) Techniques for checkpoint 11.5
  1. Ensure that the user agent default input configuration includes bindings for the following functionalities required by other checkpoints in this document:
  2. If the user agent supports the following functionalities, the default input configuration must also include bindings for them:
Sufficient techniques
  1. The user agent may satisfy the functionality of entering a URI for a new resource in a number of ways, including by prompting the user or by moving the user interface focus to a control for entering URIs.
Normative inclusions and exclusions
  1. Conformance detail: For user agent features

Note: This checkpoint does not make any requirements about the ease of use of default input configurations, though clearly the default configuration should include single-key bindings and allow easy operation. Ease of use is addressed by the configuration requirements of checkpoint 11.3.

11.6 User profiles (P2) Techniques for checkpoint 11.6
  1. For the configuration requirements of this document, allow the user to save user preferences in at least one user profile.
  2. Allow the user to choose from among available user agent default profiles, profiles created by the same user, and no profile (i.e., the user agent default settings).
Normative inclusions and exclusions
  1. This checkpoint does not require the user agent to provide multiple default profiles.
  2. This checkpoint does not require that user profiles be portable (i.e., removable from the user agent to be reread by a different instance of the user agent). Portable user profiles are very useful, however.
  3. Conformance detail: For user agent features
11.7 Tool bar configuration (P3) Techniques for checkpoint 11.7
  1. For graphical user agent user interfaces with tool bars, allow the user to configure the position of user agent user interface controls on those tool bars.
  2. Offer a predefined set of controls that may be added to or removed from tool bars.
  3. Allow the user to restore the default tool bar configuration.
Normative inclusions and exclusions
  1. Conformance detail: For user agent features

Guideline 12. Provide accessible user agent documentation and help

Checkpoints: 12.1, 12.2, 12.3, 12.4, 12.5

Ensure that the user can learn about software features that benefit accessibility from the documentation. Ensure that the documentation is accessible.

Documentation of the user interface is important, as is documentation of the user agent's underlying functionalities. While intuitive user interface design is valuable to many users, some users may still not be able to understand or be able to operate the native user interface without thorough documentation. For instance, a user with blindness may not find a graphical user interface intuitive without supporting documentation.

There are three types of requirements in this guideline:

  1. accessibility of the documentation (checkpoint 12.1)
  2. minimal requirements of what must be documented (checkpoints 12.2, 12.3, and 12.4). Documentation should include much more to explain how to install, get help for, use, or configure the user agent
  3. organization of the documentation (checkpoint 12.5)

See checkpoint 7.3 for information about following system conventions for documentation.

Checkpoint definitions

12.1 Provide accessible documentation (P1) Techniques for checkpoint 12.1
  1. Ensure that at least one version of the user agent documentation conforms to at least level Double-A of the Web Content Accessibility Guidelines 2.0 [WCAG20].
Normative inclusions and exclusions
  1. Conformance detail: For user agent features
12.2 Provide documentation of accessibility features (P1) Techniques for checkpoint 12.2
  1. Provide documentation of all user agent features that benefit accessibility.
Sufficient techniques
  1. The user agent may satisfy this checkpoint either by
    • providing a centralized view of the accessibility features, or
    • integrating accessibility features into the rest of the documentation.
    A centralized view is sufficient to satisfy this checkpoint and is required to satisfy checkpoint 12.5.
Normative inclusions and exclusions
  1. For the purposes of this checkpoint, a user agent feature that benefits accessibility is one implemented to satisfy the requirements of this document (including the requirements of checkpoints 8.1 and 7.3, and the API requirements of guideline 6).
  2. Conformance detail: For user agent features

Note: The help system should include discussion of user agent features that benefit accessibility. The user agent should satisfy this checkpoint by providing both centralized and integrated views of accessibility features in the documentation.

12.3 Provide documentation of default bindings (P1) Techniques for checkpoint 12.3
  1. Provide documentation of the default user agent input configuration (e.g., the default keyboard bindings).
Sufficient techniques
  1. If the user agent does not allow the user to override the default user agent input configuration (see checkpoint 11.3), the documentation used to satisfy this checkpoint also satisfies checkpoint 11.1.
Normative inclusions and exclusions
  1. Conformance detail: For user agent features

Note: Documentation should warn the user whenever the default input configuration is inconsistent with conventions of the operating environment.

12.4 Provide documentation of changes between versions (P2) Techniques for checkpoint 12.4
  1. Provide documentation of changes since the previous version of the user agent to features that benefit accessibility.
Normative inclusions and exclusions
  1. The features that benefit accessibility are those defined in checkpoint 12.2.
  2. Conformance detail: For user agent features
12.5 Provide dedicated accessibility section (P2) Techniques for checkpoint 12.5
  1. Provide a centralized view of all features of the user agent that benefit accessibility, in a dedicated section of the documentation.
Sufficient techniques
  1. A centralized view is required to satisfy this checkpoint and is sufficient to satisfy checkpoint 12.2.
Normative inclusions and exclusions
  1. The features that benefit accessibility are those defined in checkpoint 12.2.
  2. Conformance detail: For user agent features

Glossary Changes

Base Background: The base background is the background of the content as a whole, such that no content may be layered behind it. In graphics applications, the base background is often referred to as the canvas.).

blinking text: text whose visual rendering alternates between visible and invisible at any rate of change.

 

Glossary

This glossary is normative. However, some terms (or parts of explanations of terms) may not have an impact on conformance.

Note: In this document, glossary terms generally link to the corresponding entries in this section. These terms are also highlighted through style sheets and identified as glossary terms through markup.

a b c d e f g h i j k l m n o p q r s t u v w x y z

Activate
In this document, the verb "to activate" means (depending on context) either:

The effect of activation depends on the type of the user interface control. For instance, when a link is activated, the user agent generally retrieves the linked Web resource. When a form element is activated, it may change state (e.g., check boxes) or may take user input (e.g., a text entry field).

Alert
In this document, "to alert" means to make the user aware of some event, without requiring acknowledgement. For example, the user agent may alert the user that new content is available on the server by displaying a text message in the user agent's status bar. See checkpoint 1.3 for requirements about alerts.
Animation
In this document, an "animation" refers to content that, when rendered, creates a visual movement effect automatically (i.e., without explicit user interaction). This definition of animation includes video and animated images. Animation techniques include:
Applet
An applet is a program (generally written in the Java programming language) that is part of content, and that the user agent executes.
Application Programming Interface (API), conventional input/output/device API
An application programming interface (API) defines how communication may take place between applications.

Implementing APIs that are independent of a particular operating environment (as are the W3C DOM Level 2 specifications) may reduce implementation costs for multi-platform user agents and promote the development of multi-platform assistive technologies. Implementing conventional APIs for a particular operating environment may reduce implementation costs for assistive technology developers who wish to interoperate with more than one piece of software running on that operating environment.

A "device API" defines how communication may take place with an input or output device such as a keyboard, mouse, or video card.

In this document, an "input/output API" defines how applications or devices communicate with a user agent. As used in this document, input and output APIs include, but are not limited to, device APIs. Input and output APIs also include more abstract communication interfaces than those specified by device APIs. A "conventional input/output API" is one that is expected to be implemented by software running on a particular operating environment. For example, the conventional input APIs of the target user agent are for the mouse and keyboard. For touch screen devices or mobile devices, conventional input APIs may include stylus, buttons, and voice. The graphical display and sound card are considered conventional output devices for a graphical desktop computer environment, and each has an associated API.

Assistive technology
In the context of this document, an assistive technology is a user agent that:
  1. relies on services (such as retrieving Web resources and parsing markup) provided by one or more other "host" user agents. Assistive technologies communicate data and messages with host user agents by using and monitoring APIs.
  2. provides services beyond those offered by the host user agents to meet the requirements of users with disabilities. Additional services include alternative renderings (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, and content transformations (e.g., to make tables more accessible).

Examples of assistive technologies that are important in the context of this document include the following:

Beyond this document, assistive technologies consist of software or hardware that has been specifically designed to assist people with disabilities in carrying out daily activities. These technologies include wheelchairs, reading machines, devices for grasping, text telephones, and vibrating pagers. For example, the following very general definition of "assistive technology device" comes from the (U.S.) Assistive Technology Act of 1998 [AT1998]:

Any item, piece of equipment, or product system, whether acquired commercially, modified, or customized, that is used to increase, maintain, or improve functional capabilities of individuals with disabilities.

Attribute
This document uses the term "attribute" in the XML sense: an element may have a set of attribute specifications (refer to the XML 1.0 specification [XML] section 3).
Audio
In this document, the term "audio" refers to content that encodes prerecorded sound.
Audio-only presentation
An audio-only presentation is content consisting exclusively of one or more audio tracks presented concurrently or in series. Examples of an audio-only presentation include a musical performance, a radio-style news broadcast, and a narration.
Audio track
An audio object is content rendered as sound through an audio viewport. An audio track is an audio object that is intended as a whole or partial presentation. An audio track may, but is not required to, correspond to a single audio channel (left or right audio channel).
Audio description
An audio description (called an "auditory description" in the Web Content Accessibility Guidelines 1.0 [WCAG10]) is either a prerecorded human voice or a synthesized voice (recorded or generated dynamically) describing the key visual elements of a movie or other animation. The audio description is synchronized with (and possibly included as part of) the audio track of the presentation, usually during natural pauses in the audio track. Audio descriptions include information about actions, body language, graphics, and scene changes.
Author styles
Authors styles are style property values that come from content (e.g., style sheets within a document, that are associated with a document, or that are generated by a server).
Captions
Captions are text transcripts that are synchronized with other audio tracks or visual tracks. Captions convey information about spoken words and non-spoken sounds such as sound effects. They benefit people who are deaf or hard-of-hearing, and anyone who cannot hear the audio (e.g., someone in a noisy environment). Captions are generally rendered graphically superimposed ("on top of") the synchronized visual track.

The term "open captions" generally refers to captions that are always rendered with a visual track; they cannot be turned off. The term "closed captions" generally refers to captions that may be turned on and off. The captions requirements of this document assume that the user agent can recognize the captions as such; see the section on applicability for more information.

Note: Other terms that include the word "caption" may have different meanings in this document. For instance, a "table caption" is a title for the table, often positioned graphically above or below the table. In this document, the intended meaning of "caption" will be clear from context.

Character encoding
A "character encoding" is a mapping from a character set definition to the actual code units used to represent the data. Refer to the Unicode specification [UNICODE] for more information about character encodings. Refer to "Character Model for the World Wide Web" [CHARMOD] for additional information about characters and character encodings.
Collated text transcript
A collated text transcript is a text equivalent of a movie or other animation. More specifically, it is the combination of the text transcript of the audio track and the text equivalent of the visual track. For example, a collated text transcript typically includes segments of spoken dialogue interspersed with text descriptions of the key visual elements of a presentation (actions, body language, graphics, and scene changes). See also the definitions of text transcript and audio description. Collated text transcripts are essential for individuals who are deaf-blind.
Conditional content
Conditional content is content that, by format specification, should be made available to users through the user interface, generally under certain conditions (e.g., based on user preferences or operating environment limitations). Some examples of conditional content mechanisms include:

Specifications vary in how completely they define how and when to render conditional content. For instance, the HTML 4 specification includes the rendering conditions for the alt attribute, but not for the title attribute. The HTML 4 specification does indicate that the title attribute should be available to users through the user interface ("Values of the title attribute may be rendered by user agents in a variety of ways...").

Note: The Web Content Accessibility Guidelines 1.0 requires that authors provide text equivalents for non-text content. This is generally done by using the conditional content mechanisms of a markup language. Since conditional content may not be rendered by default, the current document requires the user agent to provide access to unrendered conditional content (checkpoints 2.3 and 2.9) as it may have been provided to promote accessibility.

Configure, control
In the context of this document, the verbs "to control" and "to configure" share in common the idea of governance such as a user may exercise over interface layout, user agent behavior, rendering style, and other parameters required by this document. Generally, the difference in the terms centers on the idea of persistence. When a user makes a change by "controlling" a setting, that change usually does not persist beyond that user session. On the other hand, when a user "configures" a setting, that setting typically persists into later user sessions. Furthermore, the term "control" typically means that the change can be made easily (such as through a keyboard shortcut) and that the results of the change occur immediately. The term "configure" typically means that making the change requires more time and effort (such as making the change via a series of menus leading to a dialog box, or via style sheets or scripts). The results of "configuration" might not take effect immediately (e.g., due to time spent reinitializing the system, initiating a new session, or rebooting the system).

In order to be able to configure and control the user agent, the user needs to be able to "write" as well as "read" values for these parameters. Configuration settings may be stored in a profile. The range and granularity of the changes that can be controlled or configured by the user may depend on limitations of the operating environment or hardware.

Both configuration and control can apply at different "levels": across Web resources (i.e., at the user agent level, or inherited from the operating environment), to the entirety of a Web resource, or to components of a Web resource (e.g., on a per-element basis).

A global configuration is one that applies across elements of the same Web resource, as well as across Web resources.

User agents may allow users to choose configurations based on various parameters, such as hardware capabilities or natural language preferences.

Note: In this document, the noun "control" refers to a user interface control.

Content
In this specification, the noun "content" is used in three ways:
  1. It is used to mean the document object as a whole or in parts.
  2. It is used to mean the content of an HTML or XML element, in the sense employed by the XML 1.0 specification ([XML], section 3.1): "The text between the start-tag and end-tag is called the element's content." Context should indicate that the term content is being used in this sense.
  3. It is used in the terms non-text content and text content.

Empty content (which may be conditional content) is either a null value or an empty string (i.e., one that is zero characters long). For instance, in HTML, alt="" sets the value of the alt attribute to the empty string. In some markup languages, an element may have empty content (e.g., the HR element in HTML).

Device-independence
In this document, device-independence refers to the desirable property that operation of a user agent feature is not bound to only one input or output device.
Document object, Document Object Model (DOM)
In general usage, the term "document object" refers to the user agent's representation of data (e.g., a document). This data generally comes from the document source, but may also be generated (e.g., from style sheets, scripts, or transformations), produced as a result of preferences set within the user agent, or added as the result of a repair performed automatically by the user agent. Some data that is part of the document object is routinely rendered (e.g., in HTML, what appears between the start and end tags of elements and the values of attributes such as alt, title, and summary). Other parts of the document object are generally processed by the user agent without user awareness, such as DTD- or schema-defined names of element types and attributes, and other attribute values such as href and id. Most of the requirements of this document apply to the document object after its construction. However, a few checkpoints (e.g., checkpoints 2.7 and 2.10) may affect the construction of the document object.
A "document object model" is the abstraction that governs the construction of the user agent's document object. The document object model employed by different user agents may vary in implementation and sometimes in scope. This specification requires that user agents implement the APIs defined in Document Object Model (DOM) Level 2 specifications ([DOM2CORE] and [DOM2STYLE]) for access to HTML, XML, and CSS content. These DOM APIs allow authors to access and modify the content via a scripting language (e.g., JavaScript) in a consistent manner across different scripting languages.
Document character set
In this document, a document character set (a concept from SGML) is a collection of abstract characters that a format specification allows to appear in an instance of the format. A document character set consists of: For instance, the character set required by the HTML 4 specification [HTML4] is defined in the Unicode specification [UNICODE]. Refer to "Character Model for the World Wide Web" [CHARMOD] for more information about document character sets.
Document source, text source
In this document, the term "document source" refers to the data that the user agent receives as the direct result of a request for a Web resource (e.g., as the result of an HTTP/1.1 [RFC2616] "GET", or as the result of viewing a resource on the local file system). The document source generally refers to the "payload" of the user agent's request, and does not generally include information exchanged as part of the transfer protocol. The document source is data that is prior to any repair by the user agent (e.g., prior to repairing invalid markup). "Text source" refers to the text portion of the document source.
Documentation
Documentation refers to information that supports the use of a user agent. This information may be found, for example, in manuals, installation instructions, the help system, and tutorials. Documentation may be distributed (e.g., some parts may be delivered on CD-ROM, others on the Web). See guideline 12 for information about documentation requirements.
Element, element type
This document uses the terms "element" and "element type" primarily in the sense employed by the XML 1.0 specification ([XML], section 3): an element type is a syntactic construct of a document type definition (DTD) for its application. This sense is also relevant to structures defined by XML schemas. The document also uses the term "element" more generally to mean a type of content (such as video or sound) or a logical construct (such as a header or list).
Enabled element, disabled element
An enabled element is a piece of content with associated behaviors that can be activated through the user interface or through an API. The set of elements that a user agent enables is generally derived from, but is not limited to, the set of interactive elements defined by implemented markup languages.

Some elements may only be enabled elements for part of a user session. For instance, an element may be disabled by a script as the result of user interaction. Or, an element may only be enabled during a given time period (e.g., during part of a SMIL 1.0 [SMIL] presentation). Or, the user may be viewing content in "read-only" mode, which may disable some elements.

A disabled element is a piece of content that is potentially an enabled element, but is not in the current session. One example of a disabled element is a menu item that is unavailable in the current session; it might be "grayed out" to show that it is disabled. Generally, disabled elements will be interactive elements that are not enabled in the current session. This document distinguishes disabled elements (not currently enabled) from non-interactive elements (never enabled).

For the requirements of this document, user selection does not constitute user interaction with enabled elements. See the definition of content focus.

Note: Enabled and disabled elements come from content; they are not part of the user agent user interface.

Note: The term "active element" is not used in this document since it may suggest several different concepts, including: interactive element, enabled element, an element "in the process of being activated" (which is the meaning of :active in CSS2 [CSS2], for example).

Equivalent (for content)
The term "equivalent" is used in this document as it is used in the Web Content Accessibility Guidelines 1.0 [WCAG10]:

Content is "equivalent" to other content when both fulfill essentially the same function or purpose upon presentation to the user. In the context of this document, the equivalent must fulfill essentially the same function for the person with a disability (at least insofar as is feasible, given the nature of the disability and the state of technology), as the primary content does for the person without any disability.

Equivalents include text equivalents (e.g., text equivalents for images, text transcripts for audio tracks, or collated text transcripts for a movie) and non-text equivalents (e.g., a prerecorded audio description of a visual track of a movie, or a sign language video rendition of a written text).

Each markup language defines its own mechanisms for specifying conditional content, and these mechanisms may be used by authors to provide text equivalents. For instance, in HTML 4 [HTML4] or SMIL 1.0 [SMIL], authors may use the alt attribute to specify a text equivalent for some elements. In HTML 4, authors may provide equivalents and other conditional content in attribute values (e.g., the summary attribute for the TABLE element), in element content (e.g., OBJECT for external content it specifies, NOFRAMES for frame equivalents, and NOSCRIPT for script equivalents), and in prose. Please consult the Web Content Accessibility Guidelines 1.0 [WCAG10] and its associated Techniques document [WCAG10-TECHS] for more information about equivalents.

Events and scripting, event handler, event type
User agents often perform a task when an event having a particular "event type" occurs, including user interface events, changes to content, loading of content, and requests from the operating environment. Some markup languages allow authors to specify that a script, called an event handler, be executed when an event of a given type occurs. An event handler is explicitly associated with an element when the event handler is associated with that element through markup or the DOM. The term "event bubbling" describes a programming style where a single event handler dispatches events to more than one element. In this case, the event handlers are not explicitly associated with the elements receiving the events (except for the single element that dispatches the events).

Note: The combination of HTML, style sheets, the Document Object Model (DOM), and scripting is commonly referred to as "Dynamic HTML" or DHTML. However, as there is no W3C specification that formally defines DHTML, this document only refers to event handlers and scripts.

Explicit user request
In this document, the term "explicit user request" refers to any user interaction through the user agent user interface (not through rendered content), the focus, or the selection. User requests are made, for example, through user agent user interface controls and keyboard bindings.
Some examples of explicit user requests include when the user selects "New viewport," responds "yes" to a prompt in the user agent's user interface, configures the user agent to behave in a certain way, or changes the selection or focus with the keyboard or pointing device.
Note: Users make mistakes. For example, a user may inadvertently respond "yes" to a prompt instead of "no." In this document, this type of mistake is still considered an explicit user request.
Focus, content focus, user interface focus, current focus
In this document, the term "content focus" (required by checkpoint 9.1) refers to a user agent mechanism that has all of the following properties:
  1. It designates zero or one element in content that is either enabled or disabled. In general, the focus should only designate enabled elements, but it may also designate disabled elements.
  2. It has state, i.e., it may be "set" on an enabled element, programmatically or through the user interface. Some content specifications (e.g., HTML, CSS) allow authors to associate behavior with focus set and unset events.
  3. Once it has been set, it may be used to trigger other behaviors associated with the enabled element (e.g., the user may activate a link or change the state of a form control). These behaviors may be triggered programmatically or through the user interface (e.g., through keyboard events).

User interface mechanisms may resemble content focus, but do not satisfy all of the properties. For example, designers of word processing software often implement a "caret" that indicates the current location of text input or editing. The caret may have state and may respond to input device events, but it does not enable users to activate the behaviors associated with enabled elements.

The user interface focus shares the properties of the content focus except that, rather than designating pieces of content, it designates zero or one control of the user agent user interface that has associated behaviors (e.g., a radio button, text box, or menu).

On the screen, the user agent may highlight the content focus in a variety of ways, including through colors, fonts, graphics, and magnification. The user agent may also highlight the content focus when rendered as synthesized speech, for example through changes in speech prosody. The dimensions of the rendered content focus may exceed those of the viewport.

In this document, each viewport is expected to have at most one content focus and at most one user interface focus. This document includes requirements for content focus only, for user interface focus only, and for both. When a requirement refers to both, the term "focus" is used.

When several viewports coexist, at most one viewport's content focus or user interface focus responds to input events; this is called the current focus.

Graphical
In this document, the term "graphical" refers to information (including text, colors, graphics, images, and animations) rendered for visual consumption.
Highlight
In this document, "to highlight" means to emphasize through the user interface. For example, user agents highlight which content is selected or focused. Graphical highlight mechanisms include dotted boxes, underlining, and reverse video. Synthesized speech highlight mechanisms include alterations of voice pitch and volume ("speech prosody").
Image
This document uses the term "image" to refer (as is commonly the case) to pictorial content. However, in this document, term image is limited to static (i.e., unmoving) visual information. See also the definition of animation.
Input configuration
An input configuration is the set of "bindings" between user agent functionalities and user interface input mechanisms (e.g., menus, buttons, keyboard keys, and voice commands). The default input configuration is the set of bindings the user finds after installation of the software; see checkpoint 12.3 for relevant documentation requirements. Input configurations may be affected by author-specified bindings (e.g., through the accesskey attribute of HTML 4 [HTML4]).
Interactive element, non-interactive element,
An interactive element is piece of content that, by specification or by programmatic enablement, may have associated behaviors to be executed or carried out as a result of user or programmatic interaction."
An interactive element is piece of content that, by specification, may have associated behaviors to be executed or carried out as a result of user or programmatic interaction. @@edit the rest@@For instance, the interactive elements of HTML 4 [HTML4] include: links, image maps, form elements, elements with a value for the longdesc attribute, and elements with event handlers explicitly associated with them (e.g., through the various "on" attributes). The role of an element as an interactive element is subject to applicability. A non-interactive element is an element that, by format specification, does not have associated behaviors. The expectation of this document is that interactive elements become enabled elements in some sessions, and non-interactive elements never become enabled elements.
Natural language
Natural language is spoken, written, or signed human language such as French, Japanese, and American Sign Language. On the Web, the natural language of content may be specified by markup or HTTP headers. Some examples include the lang attribute in HTML 4 ([HTML4] section 8.1), the xml:lang attribute in XML 1.0 ([XML], section 2.12), the hreflang attribute for links in HTML 4 ([HTML4], section 12.1.5), the HTTP Content-Language header ([RFC2616], section 14.12) and the Accept-Language request header ([RFC2616], section 14.4). See also the definition of script.
Normative, informative
What is identified as "normative" is required for conformance (noting that one may conform in a variety of well-defined ways to this document). What is identified as "informative" (sometimes, "non-normative") is never required for conformance.
Operating environment
The term "operating environment" refers to the environment that governs the user agent's operation, whether it is an operating system or a programming language environment such as Java.
Override
In this document, the term "override" means that one configuration or behavior preference prevails over another. Generally, the requirements of this document involve user preferences prevailing over author preferences and user agent default settings and behaviors. Preferences may be multi-valued in general (e.g., the user prefers blue over red or yellow), and include the special case of two values (e.g., turn on or off blinking text content).
Placeholder
A placeholder is content generated by the user agent to replace author-supplied content. A placeholder may be generated as the result of a user preference (e.g., to not render images) or as repair content (e.g., when an image cannot be found). Placeholders can be any type of content, including text, images, and audio cues.
Plug-in
A plug-in is a program that runs as part of the user agent and that is not part of content. Users generally choose to include or exclude plug-ins from their user agent.
Point of regard
The point of regard is a position in rendered content that the user is presumed to be viewing. The dimensions of the point of regard may vary. For example, it may be a point (e.g., a moment during an audio rendering or a cursor position in a graphical rendering), or a range of text (e.g., focused text), or a two-dimensional area (e.g., content rendered through a two-dimensional graphical viewport). The point of regard is almost always within the viewport, but it may exceed the spatial or temporal dimensions of the viewport (see the definition of rendered content for more information about viewport dimensions). The point of regard may also refer to a particular moment in time for content that changes over time (e.g., an audio-only presentation). User agents may determine the point of regard in a number of ways, including based on viewport position in content, content focus, and selection. The stability of the point of regard is addressed by guideline 5 and checkpoint 9.4.
Profile
A profile is a named and persistent representation of user preferences that may be used to configure a user agent. Preferences include input configurations, style preferences, and natural language preferences. In operating environments with distinct user accounts, profiles enable users to reconfigure software quickly when they log on. Users may share their profiles with one another. Platform-independent profiles are useful for those who use the same user agent on different platforms.
Prompt
In this document, "to prompt" means to require input from the user. The user agent should allow users to configure how they wish to be prompted. For instance, for a user agent functionality X, configurations might include: "always prompt me before doing X," "never prompt me before doing X," "never do X but tell me when you could have," and "never do X and never tell me that you could have."
Properties, values, and defaults
A user agent renders a document by applying formatting algorithms and style information to the document's elements. Formatting depends on a number of factors, including where the document is rendered: on screen, on paper, through loudspeakers, on a braille display, or on a mobile device. Style information (e.g., fonts, colors, and synthesized speech prosody) may come from the elements themselves (e.g., certain font and phrase elements in HTML), from style sheets, or from user agent settings. For the purposes of these guidelines, each formatting or style option is governed by a property and each property may take one value from a set of legal values. Generally in this document, the term "property" has the meaning defined in CSS 2 ([CSS2], section 3). A reference to "styles" in this document means a set of style-related properties. The value given to a property by a user agent at installation is called the property's default value.
Recognize
Authors encode information in many ways, including in markup languages, style sheet languages, scripting languages, and protocols. When the information is encoded in a manner that allows the user agent to process it with certainty, the user agent can "recognize" the information. For instance, HTML allows authors to specify a heading with the H1 element, so a user agent that implements HTML can recognize that content as a heading. If the author creates a heading using a visual effect alone (e.g., just by increasing the font size), then the author has encoded the heading in a manner that does not allow the user agent to recognize it as a heading.

Some requirements of this document depend on content roles, content relationships, timing relationships, and other information supplied by the author. These requirements only apply when the author has encoded that information in a manner that the user agent can recognize. See the section on conformance for more information about applicability.

In practice, user agents will rely heavily on information that the author has encoded in a markup language or style sheet language. On the other hand, behaviors, style, meaning encoded in a script, and markup in an unfamiliar XML namespace may not be recognized by the user agent as easily or at all. The Techniques document [UAAG10-TECHS] lists some markup known to affect accessibility that user agents can recognize.

Rendered content, rendered text
Rendered content is the part of content that the user agent makes available to the user's senses of sight and hearing (and only those senses for the purposes of this document). Any content that causes an effect that may be perceived through these senses constitutes rendered content. This includes text characters, images, style sheets, scripts, and anything else in content that, once processed, may be perceived through sight and hearing.
The term "rendered text" refers to text content that is rendered in a way that communicates information about the characters themselves, whether visually or as synthesized speech.
In the context of this document, invisible content is content that is not rendered but that may influence the graphical rendering (e.g., layout) of other content. Similarly, silent content is content that is not rendered but that may influence the audio rendering of other content. Neither invisible nor silent content is considered rendered content.
Repair content, repair text
In this document, the term "repair content" refers to content generated by the user agent in order to correct an error condition. "Repair text" refers to the text portion of repair content. Some error conditions that may lead to the generation of repair content include:

This document does not require user agents to include repair content in the document object. Repair content inserted in the document object should conform to the Web Content Accessibility Guidelines 1.0 [WCAG10]. For more information about repair techniques for Web content and software, refer to "Techniques for Authoring Tool Accessibility Guidelines 1.0" [ATAG10-TECHS].

Script
In this document, the term "script" almost always refers to a scripting (programming) language used to create dynamic Web content. However, in checkpoints referring to the written (natural) language of content, the term "script" is used as in Unicode [UNICODE] to mean "A collection of symbols used to represent textual information in one or more writing systems."
Information encoded in (programming) scripts may be difficult for a user agent to recognize. For instance, a user agent is not expected to recognize that, when executed, a script will calculate a factorial. The user agent will be able to recognize some information in a script by virtue of implementing the scripting language or a known program library (e.g., the user agent is expected to recognize when a script will open a viewport or retrieve a resource from the Web).
Selection, current selection
In this document, the term "selection" refers to a user agent mechanism for identifying a (possibly empty) range of content. Generally, user agents limit the type of content that may be selected to text content (e.g., one or more fragments of text). In some user agents, the value of the selection is constrained by the structure of the document tree.

On the screen, the selection may be highlighted in a variety of ways, including through colors, fonts, graphics, and magnification. The selection may also be highlighted when rendered as synthesized speech, for example through changes in speech prosody. The dimensions of the rendered selection may exceed those of the viewport.

The selection may be used for a variety of purposes, including for cut and paste operations, to designate a specific element in a document for the purposes of a query, and as an indication of point of regard.

The selection has state, i.e., it may be "set," programmatically or through the user interface.

In this document, each viewport is expected to have at most one selection. When several viewports coexist, at most one viewport's selection responds to input events; this is called the current selection.

See the section on the Selection label for information about implementing a selection and conformance.

Note: Some user agents may also implement a selection for designating a range of information in the user agent user interface. The current document only includes requirements for a content selection mechanism.

Serial access, sequential navigation
In this document, the expression "serial access" refers to one-dimensional access to rendered content. Some examples of serial access include listening to an audio stream or watching a video (both of which involve one temporal dimension), or reading a series of lines of braille one line at a time (one spatial dimension). Many users with blindness have serial access to content rendered as audio, synthesized speech, or lines of braille.

The expression "sequential navigation" refers to navigation through an ordered set of items (e.g., the enabled elements in a document, a sequence of lines or pages, or a sequence of menu options). Sequential navigation implies that the user cannot skip directly from one member of the set to another, in contrast to direct or structured navigation (see guideline 9 for information about these types of navigation). Users with blindness or some users with a physical disability may navigate content sequentially (e.g., by navigating through links, one by one, in a graphical viewport with or without the aid of an assistive technology). Sequential navigation is important to users who cannot scan rendered content visually for context and also benefits users unfamiliar with content. The increments of sequential navigation may be determined by a number of factors, including element type (e.g., links only), content structure (e.g., navigation from heading to heading), and the current navigation context (e.g., having navigated to a table, allow navigation among the table cells).

Users with serial access to content or who navigate sequentially may require more time to access content than users who use direct or structured navigation.

Support, implement, conform
In this document, the terms "support," "implement," and "conform" all refer to what a developer has designed a user agent to do, but they represent different degrees of specificity. A user agent "supports" general classes of objects, such as "images" or "Japanese." A user agent "implements" a specification (e.g., the PNG and SVG image format specifications or a particular scripting language), or an API (e.g., the DOM API) when it has been programmed to follow all or part of a specification. A user agent "conforms to" a specification when it implements the specification and satisfies its conformance criteria.
Synchronize
In this document, "to synchronize" refers to the act of time-coordinating two or more presentation components (e.g., a visual track with captions, or several tracks in a multimedia presentation). For Web content developers, the requirement to synchronize means to provide the data that will permit sensible time-coordinated rendering by a user agent. For example, Web content developers can ensure that the segments of caption text are neither too long nor too short, and that they map to segments of the visual track that are appropriate in length. For user agent developers, the requirement to synchronize means to present the content in a sensible time-coordinated fashion under a wide range of circumstances including technology constraints (e.g., small text-only displays), user limitations (slow reading speeds, large font sizes, high need for review or repeat functions), and content that is sub-optimal in terms of accessibility.
Text
In this document, the term "text" used by itself refers to a sequence of characters from a markup language's document character set. Refer to the "Character Model for the World Wide Web " [CHARMOD] for more information about text and characters. Note: This document makes use of other terms that include the word "text" that have highly specialized meanings: collated text transcript, non-text content, text content, non-text element, text element, text equivalent, and text transcript.
Text content, non-text content, text element, non-text element, text equivalent, non-text equivalent
As used in this document a "text element" adds text characters to either content or the user interface. Both in the Web Content Accessibility Guidelines 1.0 [WCAG10] and in this document, text elements are presumed to produce text that can be understood when rendered visually, as synthesized speech, or as Braille. Such text elements benefit at least these three groups of users:
  1. visually-displayed text benefits users who are deaf and adept in reading visually-displayed text;
  2. synthesized speech benefits users who are blind and adept in use of synthesized speech;
  3. braille benefits users who are blind, and possibly deaf-blind, and adept at reading braille.

A text element may consist of both text and non-text data. For instance, a text element may contain markup for style (e.g., font size or color), structure (e.g., heading levels), and other semantics. The essential function of the text element should be retained even if style information happens to be lost in rendering.

A user agent may have to process a text element in order to have access to the text characters. For instance, a text element may consist of markup, it may be encrypted or compressed, or it may include embedded text in a binary format (e.g., JPEG).

"Text content" is content that is composed of one or more text elements. A "text equivalent" (whether in content or the user interface) is an equivalent composed of one or more text elements. Authors generally provide text equivalents for content by using the conditional content mechanisms of a specification.

A "non-text element" is an element (in content or the user interface) that does not have the qualities of a text element. "Non-text content" is composed of one or more non-text elements. A "non-text equivalent" (whether in content or the user interface) is an equivalent composed of one or more non-text elements.

Text decoration
In this document, a "text decoration" is any stylistic effect that the user agent may apply to visually rendered text that does not affect the layout of the document (i.e., does not require reformatting when applied or removed). Text decoration mechanisms include underline, overline, and strike-through.
Text transcript
A text transcript is a text equivalent of audio information (e.g., an audio-only presentation or the audio track of a movie or other animation). It provides text for both spoken words and non-spoken sounds such as sound effects. Text transcripts make audio information accessible to people who have hearing disabilities and to people who cannot play the audio. Text transcripts are usually created by hand but may be generated on the fly (e.g., by voice-to-text converters). See also the definitions of captions and collated text transcripts.
User agent
In this document, the term "user agent" is used in two ways:
  1. The software and documentation components that together, conform to the requirements of this document. This is the most common use of the term in this document and is the usage in the checkpoints.
  2. Any software that retrieves and renders Web content for users. This may include Web browsers, media players, plug-ins, and other programs — including assistive technologies — that help in retrieving and rendering Web content.
User agent default styles
User agent default styles are style property values applied in the absence of any author or user styles. Some markup languages specify a default rendering for content in that markup language; others do not. For example, XML 1.0 [XML] does not specify default styles for XML documents. HTML 4 [HTML4] does not specify default styles for HTML documents, but the CSS 2 [CSS2] specification suggests a sample default style sheet for HTML 4 based on current practice.
User interface, user interface control
For the purposes of this document, user interface includes both:
  1. the user agent user interface, i.e., the controls (e.g., menus, buttons, prompts, and other components for input and output) and mechanisms (e.g., selection and focus) provided by the user agent ("out of the box") that are not created by content.
  2. the "content user interface," i.e., the enabled elements that are part of content, such as form controls, links, and applets.
The document distinguishes them only where required for clarity. For more information, see the section on requirements for content, for user agent features, or both.

The term "user interface control" refers to a component of the user agent user interface or the content user interface, distinguished where necessary.

User styles
User styles are style property values that come from user interface settings, user style sheets, or other user interactions.
View, viewport
The user agent renders content through one or more viewports. Viewports include windows, frames, pieces of paper, loudspeakers, and virtual magnifying glasses. A viewport may contain another viewport (e.g., nested frames). User agent user interface controls such as prompts, menus, and alerts are not viewports.

Graphical and tactile viewports have two spatial dimensions. A viewport may also have temporal dimensions, for instance when audio, speech, animations, and movies are rendered. When the dimensions (spatial or temporal) of rendered content exceed the dimensions of the viewport, the user agent provides mechanisms such as scroll bars and advance and rewind controls so that the user can access the rendered content "outside" the viewport. Examples include: when the user can only view a portion of a large document through a small graphical viewport, or when audio content has already been played.

When several viewports coexist, only one has the current focus at a given moment. This viewport is highlighted to make it stand out.

User agents may render the same content in a variety of ways; each rendering is called a view. For instance, a user agent may allow users to view an entire document or just a list of the document's headers. These are two different views of the document.

Visual-only presentation
A visual-only presentation is content consisting exclusively of one or more visual tracks presented concurrently or in series. A silent movie is an example of a visual-only presentation.
Visual track
A visual object is content rendered through a graphical viewport. Visual objects include graphics, text, and visual portions of movies and other animations. A visual track is a visual object that is intended as a whole or partial presentation. A visual track does not necessarily correspond to a single physical object or software object.
Voice browser
From "Introduction and Overview of W3C Speech Interface Framework" [VOICEBROWSER]: "A voice browser is a device (hardware and software) that interprets voice markup languages to generate voice output, interpret voice input, and possibly accept and produce other modalities of input and output."
Web resource
The term "Web resource" is used in this document in accordance with Web Characterization Terminology and Definitions Sheet [WEBCHAR] to mean anything that can be identified by a Uniform Resource Identifier (URI); refer to RFC 2396 [RFC2396].