User Agent Accessibility Guidelines 2.0

Editor's Draft 18 February 2008

This version:

http://www.w3.org/WAI/UA/2008/WD-UAAG20-20080218/WD-UAAG20-20080218.html

Latest version:

N/A

Previous version:

http://www.w3.org/WAI/UA/2008/WD-UAAG20-20080110/WD-UAAG20-20080110.html

Editors:

James Allan, Texas School for the Blind and Visually Impaired

Jan Richards, Adaptive Technology Resource Centre, University of Toronto

Previous Editors:

NA

Copyright ©2007 W3C^® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.

Abstract

This document provides guidelines for designing user agents that lower barriers to Web accessibility for people with disabilities (visual, hearing, physical, cognitive, and neurological). User agents include browsers and other types of software that retrieve and render Web content. A user agent that conforms to these guidelines will promote accessibility through its own user interface and through other internal facilities, including its ability to communicate with other technologies (especially assistive technologies). Furthermore, all users, not just users with disabilities, should find conforming user agents to be more usable.

In addition to helping developers of browsers and media players, this document will also benefit developers of assistive technologies because it explains what types of information and control an assistive technology may expect from a conforming user agent. Technologies not addressed directly by this document (e.g., technologies for braille rendering) will be essential to ensuring Web access for some users with disabilities.

The "User Agent Accessibility Guidelines 2.0" (UAAG 2.0) is part of a series of accessibility guidelines published by the W3C Web Accessibility Initiative (WAI).

Status of this document

May be Superseded

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

Editor's Draft of ATAG 2.0

This is an internal Editor's Draft.

The Working Group (UAWG) intends to publish UAAG 2.0 as a W3C Recommendation. Until that time User Agent Accessibility Guidelines 1.0 (UAAG 1.0) [UAAG10] is the stable, referenceable version. This Working Draft does not supersede UAAG 1.0.

Web Accessibility Initiative

This document has been produced as part of the W3C Web Accessibility Initiative (WAI). The goals of the AUWG are discussed in the Working Group charter. The AUWG is part of the WAI Technical Activity.

No Endorsement

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

Patents

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Introduction

This section is informative.

This document specifies requirements that, if satisfied by user agent developers, will lower barriers to accessibility. This document includes the following:

• This introduction provides context for understanding the requirements listed in section 2.
• Section 2 explains 12 general principles of accessible design, called "guidelines." Each guideline consists of a list of requirements, called "checkpoints," which must be satisfied in order to conform to this document. Note: Section 2 is numbered differently than the other sections; it consists of a list of guidelines. In section 2, "checkpoint 1.2" refers to the second checkpoint of the first guideline. "Section 1.2" refers to a subsection of the Introduction.
• Section 3 explains how to make claims that software components satisfy the requirements of section 2.
• An appendix offers a summary of this document's principal goals and structure [UAAG10-SUMMARY].
• A second appendix lists all the checkpoints for convenient reference (e.g., as a tool for developers to evaluate software for conformance) [UAAG10-CHECKLIST].

A separate document, entitled "Techniques for User Agent Accessibility Guidelines 1.0" (the "Techniques document" from here on) [UAAG10-TECHS], provides suggestions and examples of how each checkpoint might be satisfied. It also includes references to other accessibility resources (such as platform-specific software accessibility guidelines) that provide additional information on how a user agent may satisfy each checkpoint. The techniques in the Techniques document are informative examples only, and other strategies may be used or required to satisfy the checkpoints. The UAWG expects to update the Techniques document more frequently than the current guidelines. Developers, W3C Working Groups, users, and others are encouraged to contribute techniques.

1.1 Relation to WAI accessibility guidelines

"User Agent Accessibility Guidelines 1.0" (UAAG 1.0) is part of a series of accessibility guidelines published by the Web Accessibility Initiative (WAI). The documents in this series reflect an accessibility model in which Web content authors, format designers, and software developers have roles in ensuring that users with disabilities have access to the Web. The accessibility-related interests of these stakeholders intersect and complement each other as follows:

• Designers of formats (e.g., HTML, XHTML, XML, SVG, SMIL, MathML, and XForms) and protocols (e.g., HTTP) create specifications that allow communication on the Web. Format designers include features in these specifications that authors should use to create accessible content and that user agents should support through an accessible user interface. The "XML Accessibility Guidelines (XAG)" [XAG10] explains the responsibilities of XML format designers; many XAG requirements make sense for non-XML formats as well.
• Authors make use of the accessibility features of different format specifications, use markup appropriately, write in clear and simple language, and organize a Web site consistently. The "Web Content Accessibility Guidelines 1.0" [WCAG10] explains the responsibilities of authors in meeting the needs of users with disabilities. The "Web Content Accessibility Guidelines (WCAG) 1.0" is considered within UAAG 1.0 to be the reference set of requirements to make Web content accessible. The "Authoring Tool Accessibility Guidelines 1.0" [ATAG10] explains the responsibilities of authoring tool developers. An accessible authoring tool facilitates the creation of accessible Web content and may be operated by users with disabilities.
• User agent developers design software that meets the needs of users with disabilities through conformance to other specifications, an accessible user interface, accessible documentation, and communication with other software (notably assistive technologies).

The requirements of this document interact with those of the "Web Content Accessibility Guidelines 1.0" [WCAG10] in a number of ways:

• UAAG 1.0 checkpoint 8.1 requires implementation of the accessibility features of specifications. Features are those identified as such and those that satisfy all of the requirements of WCAG 1.0 [WCAG10].
• UAAG 1.0 checkpoint 12.1 requires conformance to WCAG 1.0 for user agent documentation.
• UAAG 1.0 also incorporates some terms and concepts from WCAG 1.0, a consequence of fact that the documents were designed to complement one another.

Some requirements of this document take into account limitations of formats, authors, and designers. For example, formats generally do not enable authors to encode all of their knowledge in a way that a user agent can fully recognize. A format may lack features required for accessibility. An author may not make use of the accessibility features of a format or may misuse a format (which can cause problems for user agents). A user agent designer may not implement a format specification correctly or completely.

Some of these limitations are taken into account as follows:

• UAAG 1.0 includes requirements to satisfy the expectations set by WCAG 1.0 "until user agent" clauses. These clauses make additional requirements of authors in order to compensate for some limitations of deployed user agents.
• UAAG 1.0 includes several repair requirements (e.g., checkpoints checkpoint 2.7 and checkpoint 2.10) for cases where content does not conform to WCAG 1.0. Furthermore, this document includes some requirements to address certain widespread authoring practices that are discouraged because they may cause accessibility or usability problems (e.g., some uses of HTML frames).
• Except for the indicated repair checkpoints, UAAG 1.0 only requires user agents to handle what may be recognized through protocols and formats. For example, user agents are not expected to recognize that the author has used "clear and simple" language to express ideas (WCAG 1.0, checkpoint 14.1). See the section on checkpoint applicability for more information about what the user agent is expected to recognize.

The Web Accessibility Initiative provides other resources and educational materials to promote Web accessibility. Resources include information about accessibility policies, links to translations of WAI materials into languages other than English, information about specialized user agents and other tools, accessibility training resources, and more.

1.2 Target user agents

This document was designed specifically to improve the accessibility of user agents with multimedia capabilities running in the following type of environment (typically that of a desktop computer):

• The operating environment includes a keyboard (or keyboard equivalent)
• Assistive technologies may be used in the operating environment and may communicate with the conforming user agent

The target user agent is one designed for the general public to handle general-purpose content in ordinary operating conditions.

This document does not forbid conformance by other types of user agents, but some requirements (e.g., implementation of certain application programming interfaces, or APIs) are not likely to be satisfied in environments (e.g., handheld devices or kiosks) other than the target environment. Future work by the UAWG may address the accessibility of user agents running on handheld devices, for example.

Technologies not addressed directly by this document (e.g., those for braille rendering) will be essential to ensuring Web access for some users with disabilities. Note that the ability of conforming user agents to communicate well with assistive technologies will depend in part on the willingness of assistive technology developers to follow the same standards and conventions for communication.

1.2.1 Composition of conforming user agents

In general, a conforming user agent will consist of several coordinated components, such as a Web browser, a multimedia player, several plug-ins, features or applications provided by the operating environment, and documentation distributed with the software or available on the Web. These components may run on the user's computer or on a server. A conforming user agent may also include assistive technologies and applications provided by the operating environment. The current document places no restrictions on the type or number of components used for conformance.

This does not mean that every component that one has chosen as part of the user agent has to satisfy every single requirement; some requirements may not be relevant for a particular component. For instance, if a component does not have a user interface, the user interface requirements would not be relevant. On the other hand, if a component has a user interface, the user interface requirements are relevant. Conformance addresses the composite user agent as a whole.

1.2.2 Use of operating environment features

The UAWG encourages developers to satisfy the requirements of this document by adopting operating environment conventions and features that benefit accessibility. When an operating environment feature (e.g., the operating system's audio control panel, including its user interface) is adopted to satisfy the requirements of this document, it is part of the user agent.

See additional information on conformance of user agents running in multiple operating environments.

1.3 Known limitations of this document

People with (or without) disabilities access the Web with widely varying sets of capabilities, software, and hardware. Some users with disabilities:

• May not be able to see, hear, move, or speak.
• May not be able to perceive, read, or process some types of information easily or at all.
• May not have or be able to use a keyboard or pointing device.

This document does not include requirements to meet all known accessibility needs. Some known limitations of this document include the following:

Input modalities

This document only includes requirements for keyboard, pointing device, and voice input modalities. This document includes several checkpoints related to voice input as part of general input requirements (e.g., the checkpoints of guideline 7 and guideline 11) but does not otherwise address voice-based navigation or control.

Note: The UAWG intends to coordinate further work on the topics of voice input and synthesized speech rendering with groups in W3C's Voice Browser Activity and Multimodal Interaction Activity.

Output modalities

This document does not include requirements for braille rendering. Some requirements are specific to graphical rendering and others specific to audio output or synthesized speech output. Speech rendering requirements are made by checkpoint 4.9 to checkpoint 4.13. Many of the requirements of this document are generic enough to apply to a variety of output modalities, including braille. User agents conform to this document by supporting some combination of graphical and audio/speech rendering output; see the section on Content type labels for more information.

Size and color of non-text content

This document includes some checkpoints to ensure that the user is able to control the size and color of visually rendered text content (checkpoints 4.1 and 4.3). This document does not in general address control of the size and color of visually rendered non-text content (e.g., images).

Note: A user agent may implement resizing functionalities as part of conformance to other specifications (e.g., Scalable Vector Graphics [SVG]).

Background image interference

The requirement of checkpoint 3.1 to allow the user to turn off rendering of background images does not extend to multi-layered rendering.

User control of every user interface component

This document distinguishes user interface features that are part of the user agent user interface and those that are part of content. Some checkpoints (e.g., those in guideline 5) require user control over rendering and behavior that is driven by content only. This document does not always explicitly require the same control over features of the user agent user interface. Nevertheless, this document (see checkpoint 7.3) does require user agents to follow software usability guidelines. The UAWG expects such usability guidelines to include requirements for user control over user interface behavior.

Note: It is more difficult for users to distinguish content from user interface when both are rendered as sound in one temporal dimension, than it is when both are rendered visually in two spatial dimensions. Thus, the UAWG encourages developers of user agents that include audio output or synthesized speech output to apply the requirements of this document to both content and user agent components.

Time parameters

This document includes requirements (see checkpoints 2.4, 4.4, 4.5, and 4.9) for control of some time parameters. The requirements are for time parameters that the user agent recognizes and controls. This document does not include requirements for control of time parameters managed on the server.

Digital rights management

The User Agent Accessibility Guidelines Working Group recognizes that further work is necessary in the area of digital rights management as it relates to accessibility. Digital rights management refers to methods of describing and perhaps enforcing intellectual property associated with Web resources.

Note: The User Agent Accessibility Guidelines Working Group may address these and other topics in a future version of the User Agent Accessibility Guidelines. Even though UAAG 1.0 does not address these topics, the UAWG encourages user agent developers to consider them in their designs.

1.4 Relation to general software design guidelines and other specifications

One the goals of the authors of this document is to ensure that the requirements are compatible with other good software design practices. However, this document does not purport to be a complete guide to good software design. For instance, the general topic of user interface design for computer software exceeds the scope of this document, though some user interface requirements have been included because of their importance to accessibility. The Techniques document [UAAG10-TECHS] includes some references to general software design guidelines and platform-specific accessibility guidelines (in particular, see checkpoint 7.3). Involving people with disabilities in the design and testing of software will generally improve the accessibility of the software.

This document promotes conformance to other specifications as part of accessible design. Conformance to specifications makes it easier to design assistive technologies, and helps ensure the implementation of built-in accessibility functions.

This document also includes some requirements to implement an accessibility feature that may only be optional in another specification.

In rare cases, a requirement in UAAG 1.0 may conflict with a requirement in another specification. UAAG 1.0 does not define a process for resolving such conflicts. The authors of this document anticipate that developers will consider accessibility implications in determining how to resolve them.

1.4.1 Installation

Installation is an important aspect of both accessibility and general software usability. On platforms where a user can install a user agent, the installation (and update) procedures need to be accessible. Furthermore, the installation procedure should provide and install all components necessary to satisfy the requirements of this document, since the risk of installation failure increases with the number of components (e.g., plug-ins) to be installed.

This document does not include a checkpoint requiring that installation procedures be accessible. Since this document considers installation to be part of software usage, the different aspects of installation (e.g., user interface, documentation, and operating environment conventions) are already covered by the complete set of checkpoints.

1.5 Security considerations

Some of the requirements of this document may have security implications, such as communication through APIs, and allowing programmatic read and write access to content and user interface control. This document assumes that features required by this document will be built on top of an underlying security architecture. Consequently, unless permitted explicitly in a checkpoint (as in checkpoint 6.5), this document grants no conformance exemptions based on security issues.

Developers should design user agents that enable communication with trusted assistive technologies. Sensitive information that the user agent can access through the user agent's user interface should also be available to assistive technologies through secure means. For instance, if the user types a password in the user agent user interface, do not communicate substitute characters (such as asterisks) through an API, but rather the real password, properly encrypted.

Note also that appropriate user agent behavior with respect to security may depend on the user's context. For instance, hiding typed passwords with asterisks is much less important for someone alone in a room than for someone in a crowded room. Similarly, while unencrypted passwords rendered as synthesized speech should not be broadcast in a crowded room, they may pose no security risk if the user is wearing an earphone.

For information related to security, refer to "XML-Signature Syntax and Processing" [XMLDSIG] and "XML Encryption Syntax and Processing" [XMLENC].

1.6 User control

This document emphasizes the goal of ensuring that users, including users with disabilities, have control over their environment for accessing the Web. Key methods for achieving that goal include: optional self-pacing, configurability, device-independence, interoperability, direct support for both graphical and auditory output, and adherence to published conventions. Chapter 2 addresses these issues in detail.

This document also acknowledges the importance of author preferences and the proper implementation of specifications. However, this document includes requirements to override certain author preferences when the user would not otherwise be able to access that content.

1.6.1 Control of automatic behavior

Many of the requirements in this document give the user additional control over behavior that would otherwise occur automatically. For instance, there is a requirement to allow configuration to not open a viewport automatically (checkpoint 5.3) and one that requires user confirmation before submitting a form (checkpoint 5.5). This type of manual configuration option may be essential for some users with disabilities, since automatic behavior may be disorienting or interfere with navigation.

1.6.2 Configurability

This document includes requirements for users with a variety of disabilities, in part because some users may have more than one disability. In some cases, it may appear that two requirements contradict each other. For instance, a user with a physical disability may prefer that the user agent offer more automatic behavior (to reduce demand for physical effort) than a user with a cognitive disability (for whom automatic behavior may cause confusion). Thus, many of the requirements in this document involve configuration as one way to ensure that a functionality designed to improve accessibility for one user does not interfere with accessibility for another. Also, since a default user agent setting may be useful for one user but interfere with accessibility for another, this document prefers configuration requirements to requirements for default settings. Finally, there may be some cases where, for some content, a feature required by this document is ineffective or causes content to be less accessible, making it imperative that the user be able to turn off the feature.

To avoid overwhelming users with an abundance of configuration options, this document includes requirements that promote ease of configuration and documentation of accessibility features (see guideline 12).

1.6.3 Device independence, spatial independence, and temporal independence

Many requirements in this document promote different kinds of independence:

• Input and output device independence. This document includes some requirements to promote device-independence natively, as well as requirements for interoperability with assistive technologies that provide complementary input and output functionalities.
• Spatial independence. Some users may not navigate effectively in two-dimensional visual space (e.g., users who do not use a pointing device) or may be constrained to one temporal dimension (e.g., users of audio-only output).
• Temporal independence. Some users (e.g., users with a physical or cognitive disability) may not be able to interact with content that changes over time, or interaction with content that is time-sensitive.

1.6.4 Additional benefits of accessible user agent design

In meeting the goals of users with disabilities, user agent developers will also improve access to the Web for users in general. For example, users without disabilities:

• may have a text-only screen, a small screen, or a slow Internet connection (e.g., via a mobile phone browser). These users are likely to benefit from the same features that provide access to people with low vision or blindness.
• may be in a situation where their eyes, ears, or hands are busy or interfered with (e.g., driving to work or working in a noisy environment). These users are likely to benefit from the same features that provide access to people who cannot use a mouse or keyboard due to a visual, hearing, or physical disability.
• may not understand fluently the natural language of spoken content. These users are likely to benefit from the same visual rendering of text equivalents that make spoken language accessible to people with a hearing disability.

The UAWG expects that software which satisfies the requirements of this document will be more flexible, manageable, extensible, and beneficial to all users. For example, a user agent architecture that allows programmatic access to content and the user interface will encourage software modularity and reuse, and will enable operation by scripting tools and automated test engines in addition to assistive technologies.

UAAG 2.0 Guidelines

PRINCIPLE 1. Support the accessibility features of all implemented specifications

8.1 Implement accessibility features (P1) Techniques for checkpoint 8.1

1. A: Implement the accessibility features listed in the technology accessibility features benchmark for all technologies listed in the conformance profile.@@8.1@@

PRINCIPLE 2. Authoring tool must facilitate access by assistive technologies

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]:
   • Document Information item: children, document element, base URI, charset
   • Element Information items: element-type name, children, attributes, parent
   • Attribute Information items: attribute-type name, normalized value, specified, attribute type, references, owner element
   • Character Information items: character code, parent element
   • Comment Information items: content, parent
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:
   • for HTML: the Core module
   • for XML: the Core and XML modules
2. As part of satisfying provision one of this checkpoint:
   • In the Java and ECMAScript operating environments, export the normative bindings specified in the DOM Level 2 Core Specification [DOM2CORE], or
   • In other operating environments, the exported bindings (e.g., C++) must be publicly documented.

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:
   • The API is defined by a W3C Recommendation, or the API is publicly documented and designed to enable interoperability with assistive technologies.
   • If no such API is available, or if available APIs do not enable the user agent to satisfy the requirements,
     • implement at least one publicly documented API to satisfy the requirements, and
     • follow operating environment conventions for the use of input and output APIs.

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.

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.

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:
   • Follow operating environment conventions.
   • If no conventions exist, implement publicly documented APIs.

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.

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:
   • In the Java and ECMAScript operating environments, export the normative bindings specified in the CSS module of the DOM Level 2 Style Specification [DOM2STYLE], or
   • In other operating environments, the exported bindings (e.g., C++) must be publicly documented.

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.

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.

1.1 Full keyboard access (P1) Techniques for checkpoint 1.1

@@7.2, 7.4 Possibly move here@@

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

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

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

1.3 Text alternatives for non-text objects (P1) Techniques for checkpoint 1.3

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.

2.4 Allow time-independent interaction (P1) Techniques for checkpoint 2.4

1. Where time limits for user input are recognized and controllable by the user agent, provide an option to extend the time limit.

5.5 Help users avoid and correct mistakes (P2) Techniques for checkpoint 5.5

1. User has the option to confirm (or cancel) any form submission that is made on the basis of an action that occurs while content focus is not on the submitting control (e.g., forms that submit when Enter is pressed).@@5.5@@

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).

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.

12.1 Document the user interface including all accessibility features

1. A:At least one version of the documentation is either:
   • (a) "A" Accessible: Web content and conforms to WCAG 2.0 Level "A" (although it is not necessary for the documentation to be delivered on-line), or
   • (b) Accessible Platform Format: not Web content and conforms to a published accessibility benchmark that is identified in the conformance claim (e.g., when platform-specific documentation systems are used).
2. A: Provide documentation of all user agent features that benefit accessibility.@@12.2@@
3. AA: Provide documentation of changes since the previous version of the user agent to features that benefit accessibility.@@12.4@@
4. AA: Provide a centralized view of all features of the user agent that benefit accessibility, in a dedicated section of the documentation.@@12.5@@
5. AAA: Provide context-sensitive help on all user agent features that benefit accessibility.

2.1 Render content according to specification (P1) Techniques for checkpoint 2.1

1. A: Render content according to technology specification (e.g., for a markup language or style sheet language). Note: This includes any accessibility features of the technology.
2. AA: If the user agent does not render a technology, it should allow the user to choose a way to handle content in that technology (e.g., by launching another application or by saving it to disk).

2.2 Provide text view (P1) Techniques for checkpoint 2.2

1. A: For content authored in text formats, provide a view of the text source.

2.X Make text alternatives for any non-text content and synchronized alternatives for synchronized media available (P1) Techniques for checkpoint 2.X

1. A: Make text alternatives for any non-text content (e.g., short text alternatives, long descriptions, text transcripts, collated text transcripts) available (e.g., via a conditional content stack).
2. A: Make synchronized alternatives for synchronized media (e.g., captions, audio descriptions, sign language) available at the same time as the associated audio tracks and visual tracks.

2.X Manage conditional content (P1) Techniques for checkpoint 2.X

New Technique 2.3.5=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.

X.Y Provide access to relationship information @@NEW 10.1 - also clicking on labels changes checkbox etc.?@@

10.2 Highlight selection, content focus, enabled elements, visited links (P1) Techniques for checkpoint 10.2 @@http://lists.w3.org/Archives/Public/w3c-wai-ua/2008JanMar/0030.html@@

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:
   • differ from each other, and
   • do not rely on rendered text foreground and background colors alone.
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:
   • for text size, the range required by provision three of checkpoint 4.1.
   • for font family, the range required by provision three of checkpoint 4.2.
   • for text foreground and background colors and decorations, the range offered by the conventional utility available in the operating environment for users to choose rendered text colors or decorations (e.g., the standard font and color dialog box resources supported by the operating system). If no such utility is available, the range supported by the conventional APIs of the operating environment for specifying text colors or drawing text.
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.
5. AA: Extend the functionality required by provision two of checkpoint 10.2 by allowing configuration through a single setting.@@10.3@@

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.

2.6 Respect synchronization cues (P1) Techniques for checkpoint 2.6

1. Respect synchronization cues (e.g., in markup) during rendering.

2.7 Repair missing content (P2) Techniques for checkpoint 2.7

1. A: User have the option of receiving generated repair text when the user agent recognizes that the author has not provided conditional content required by the format specification.@@from 2.7@@
2. AAA: User have the option of receiving generated repair text when the user agent recognizes that the author has provided conditional content required by the format specification, but it is empty content.@@from 2.8@@

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:
   • generate no repair text.
   • generate repair as described in checkpoint 2.7.

2.9 Render conditional content automatically (P3) Techniques for checkpoint 2.9

1. User has the option 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.

2.10 Do not render text in unsupported writing systems (P3) Techniques for checkpoint 2.10

1. AAA: Users have the option to turn off rendering of text content for in any unsupported writing systems and instead indicate to the user in context that author-supplied content has not been rendered due to lack of support for a writing system

2.X Allow configuration not to render some content that may reduce accessibility Techniques for checkpoint 3.1

1. A: User has the option not to render background images (i.e., images that are rendered on the base background).
2. A: User has the option not to render recognized audio, video, or animated image content, except on explicit user request.
3. A: User has the option to render recognized animated or blinking text content as motionless, unblinking text.
4. A: User has the option not to execute any recognized executable content (e.g., scripts, objects and applets).
5. AA: User has the option not to render image content.

Note: When the user has opted not to render or execute specific content, it is considered conditional content. See checkpoint 2.3 for information about providing access to conditional content.

@@Tech=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)
@@Tech=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)

2.X Toggle automatic content retrieval (P1) Techniques for checkpoint 3.4

1. User has the option so that the user agent only retrieves content on explicit user request.

Note: When the user chooses not to retrieve (fresh) content, the user agent may ignore that content; buffering is not required.@@WEB2.0 content may completely break@@

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."

4.1 Configure text scale (P1) Techniques for checkpoint 4.1@@ENSURE CONFIGURATION SETTINGS ARE SAVED

1. User has the option to globally increase or decrease the scale (i.e., the general size of text) of visually rendered text content, overriding text sizes specified by the author or user agent defaults.
2. When rendered text is rescaled, preserve distinctions in the size of rendered text (e.g., headers continue to be larger than body text).
3. The rescale option offers a range of text sizes that includes at least:
   • the range offered by the conventional utility available in the operating environment that allows users to choose the text size (e.g., the font size), or
   • if no such utility is available, the range of text sizes supported by the conventional APIs of the operating environment for drawing text.

4.2 Configure font family (P1) Techniques for checkpoint 4.2

1. User has the option to globally set the font family of all visually rendered text content, overriding font families specified by the author or user agent defaults.
2. The font family changing option offers a range of font families to the user that includes at least:
   • the range offered by the conventional utility available in the operating environment that allows users to choose the font family, or
   • if no such utility is available, the range of font families supported by the conventional APIs of the operating environment for drawing text.

4.3 Configure text colors (P1) Techniques for checkpoint 4.3

1. User has the option to globally set the foreground and background color of all visually rendered text content, overriding the colours specified by the author or user agent defaults.
2. As part of satisfying provision one of this checkpoint, offer a range of colors to the user that includes at least:
   • the range offered by the conventional utility available in the operating environment that allows users to choose colors, or
   • if no such utility is available, the range of colors supported by the conventional APIs of the operating environment for specifying colors.

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.

4.4 Control multimedia (P1) Techniques for checkpoint 4.4

1. A: The user can slow the presentation rate of recognized rendered audio and animation content (including video and animated images), such that both of the following are true:
   • for a visual track, provide at least one setting between 40% and 60% of the original speed.
   • for a prerecorded audio track including audio-only presentations, provide at least one setting between 75% and 80% of the original speed.
   • when audio and video tracks are synchronized: above 80% of the original speed, maintain synchronization; below 80% the user agent is not required to render the audio track.
2. A: 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.
3. 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.

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.

4.6 Do not obscure captions (P1) Techniques for checkpoint 4.6

1. For graphical viewports, User has the option so that captions synchronized with a visual track in content are not obscured by it.

4.7 Manage volume control (P1) Techniques for checkpoint 4.7

1. User has the option to globally set the volume of all rendered audio tracks (including a "mute" setting) through available operating environment mechanisms.
2. If the user agent can recognize speech and non-speech audio tracks, then the volume of these two types of audio tracks can be set independently.

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.

4.9 Configure text rendering via synthesized speech (P1) Techniques for checkpoint 4.9

1. A: The speech synthesizer must include the following characteritics, controllable by the user, overriding any values specified by the author: @@4.9,4.10@@
   • (a) speech rate and
   • (b) speech volume (independently of other sources of audio).
2. A: User can set all of the speech characteristics offered by the speech synthesizer, according to the full range of values available, overriding any values specified by the author: @@4.11@@
3. AA: User can set the following synthesized speech characteristics, overriding any values specified by the author: @@4.12@@
   • (a) pitch ("pitch" refers to the average frequency of the speaking voice),
   • (b) pitch range ("pitch range" specifies a variation in average frequency), and
   • (c) speech stress. ("speech stress" refers to the height of "local peaks" in the intonation contour of the voice).@@richness deleted since not in CSS3 http://www.w3.org/TR/2004/WD-css3-speech-20041216/@@
4. AA: Provide support for all of the following speech features:
   1. (a) user-defined extensions to the synthesized speech dictionary,
   2. (b) "spell-out", where text is spelled one character at a time, or according to language-dependent pronunciation rules,
   3. (c) at least two ways of speaking numerals: one where numerals are spoken as individual digits, and one where full numbers are spoken, and
   4. (d) at least two ways of speaking punctuation: one where punctuation is spoken literally, and one where punctuation is rendered as natural pauses.

4.14 Choose style sheets (P1) Techniques for checkpoint 4.14

1. If the author has supplied one or more style sheets, the user has the following options:
   • (a) select between the style sheets, or
   • (b) turn off the style sheets.
2. If the user has supplied one or more style sheets, the user has the following options:
   • (a) select between the style sheets, or
   • (b) turn off the style sheets.

5.1 No automatic content focus change (P2) Techniques for checkpoint 5.1

1. User has the option so that if a viewport opens without explicit user request, neither its content focus nor its user interface focus automatically becomes the current focus.

5.2 Keep viewport on top (P2) Techniques for checkpoint 5.2

1. For graphical user interfaces, User has the option 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. User has the option 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.

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.

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

7.X Observe operating environment conventions (@@Guideline A.1.3@@)

Note: 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.

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.

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).

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.

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.

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: 5.X Manage viewport opening

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).

9.X Focus Management

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.

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.

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.

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.

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.

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.

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.

9.8 Provide text search (P2) Techniques for checkpoint 9.8@@OPERABLE@@

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:
   • move the viewport so that the matched text content is at least partially within it, and
   • allow the user to search for the next instance of the text from the location of the match.
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.

9.9 Allow structured navigation (P1) Techniques for checkpoint 9.9@@OPERABLE@@

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.

9.10 Configure important elements (P3) Techniques for checkpoint 9.10@@NOT DONE@@

1. User has the option of the set of important elements and attributes (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.

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.

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).

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:
   • link element content,
   • link title,
   • whether the link is internal to the resource (e.g., the link is to a target in the same Web page),
   • whether the user has traversed the link recently, and
   • information about the type, size, and natural language of linked Web resources.

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.

11.2 Current author input configuration (P2) Techniques for checkpoint 11.2

1. Provide a centralized view of the current author-specified input configuration.

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.

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.

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:
   • move content focus to the next enabled element in document order, and move content focus to the previous enabled element in document order (checkpoints 9.3 and 9.7);
   • activate the link designated by the content focus (checkpoints 1.1 and 9.1);
   • search for text, search again for same text (checkpoint 9.8);
   • increase the scale of rendered text, and decrease the scale of rendered text (checkpoint 4.1);
   • increase global volume, and decrease global volume (checkpoint 4.7); and
   • stop, pause, resume, and navigate efficiently selected audio and animations, including video and animated images (checkpoint 4.5).
2. If the user agent supports the following functionalities, the default input configuration must also include bindings for them:
   • next history state (forward), and previous history state (back);
   • enter a URI for a new resource;
   • add a URI to favorites (i.e., bookmarked resources);
   • view favorites;
   • reload a resource;
   • interrupt a request to load or reload a resource;
   • for graphical viewports: navigate forward and backward through rendered content by approximately the height of the viewport; and
   • for user agents that render content in lines of (at least) text: move the point of regard to the next and previous line.

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.

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).

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.

Activate

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

• To execute or carry out one or more behaviors associated with an enabled element.
• To execute or carry out one or more behaviors associated with a component of the user agent user interface.

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:

• graphically displaying a sequence of snapshots within the same region (e.g., as is done for video and animated images). The series of snapshots may be provided by a single resource (e.g., an animated GIF image) or from distinct resources (e.g., a series of images downloaded continuously by the user agent).
• scrolling text (e.g., achieved through markup or style sheets).
• displacing graphical objects around the viewport (e.g., a picture of a ball that is moved around the viewport giving the impression that it is bouncing off of the viewport edges). For instance, the SMIL 2.0 [SMIL20] animation modules explain how to create such animation effects in a declarative manner (i.e., not by composition of successive snapshots).

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:

• screen magnifiers, which are used by people with visual disabilities to enlarge and change colors on the screen to improve the visual readability of rendered text and images.
• screen readers, which are used by people who are blind or have reading disabilities to read textual information through synthesized speech or braille displays.
• voice recognition software, which may be used by people who have some physical disabilities.
• alternative keyboards, which are used by people with certain physical disabilities to simulate the keyboard.
• alternative pointing devices, which are used by people with certain physical disabilities to simulate mouse pointing and button activations.

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 should be made available to users only under certain conditions (e.g., based on user preferences or operating environment limitations). Some examples include:

• The alt attribute of the IMG element in HTML 4 [HTML4].
• OBJECT elements in HTML 4 [HTML4].
• The switch element and test attributes in SMIL 1.0 [SMIL].
• The NOSCRIPT and NOFRAMES elements in HTML 4 [HTML4].

Note: Specifications vary in how completely they define how and when to render conditional content.
Conditional content stack: The set of conditional content items for a given position in content. The items may be mutually exclusive (e.g., regular contrast graphic vs. high contrast graphic) or non-exclusive (e.g., caption track that can play at the same time as a sound track).

Configure, control, user option

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.@@POINT TO NEW CHECKPOINT ON HOW TO SAVE SETTTINGS@@

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:

• A "repertoire": A set of abstract characters, such as the Latin letter "A," the Cyrillic letter "I," and the Chinese character meaning "water."
• Code positions: A set of integer references to characters in the repertoire.

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.

Important elements

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.

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 [WCAG 2.0, ATAG 2.0]

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 [ATAG 2.0]

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 [ATAG 2.0]

Any user agent initiated request for a decision or piece of information from users.

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:

• Erroneous or incomplete content (e.g., ill-formed markup, invalid markup, or missing conditional content that is required by format specification);
• Missing resources for handling or rendering content (e.g., the user agent lacks a font family to display some characters, or the user agent does not implement a particular scripting language).

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.

technology (Web content) - or shortened to technology [WCAG 2.0, ATAG 2.0]

A mechanism for encoding instructions to be rendered, played or executed by user agents. Web Content technologies may include markup languages, data formats, or programming languages that authors may use alone or in combination to create end-user experiences that range from static Web pages to multimedia presentations to dynamic Web applications. Some common examples of Web content technologies include HTML, CSS, SVG, PNG, PDF, Flash, and JavaScript.

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 format

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].

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.

"Top-Level" Viewports are viewports that are not contained within other user agent viewports.

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].

Appendix E: Checklist

Appendix F: Comparison of UAAG 1.0 guidelines to UAAG 2.0