User Agent Accessibility Guidelines 1.0

3. Conformance

This normative section defines what it means to conform to this document and explains how to make a valid conformance claim. Please note that this document includes both conformance requirements and conformance claim requirements.

Here is a sample claim (expressed in HTML):

In this document (notably in the checkpoints and in this section on conformance), the terms "must", "should", and "may" (and related terms) are used in accordance with RFC 2119 [RFC2119]. This section uses the expression "subject of a claim" to refer to a user agent about which someone wishes to claim some level of conformance to this document. The subject of a claim may be one or more software components (e.g., a browser plus additional software).

Note: Conformance to the requirements of this document is expected to be a strong indicator of accessibility, but it is neither a necessary nor sufficient condition for ensuring the accessibility of software. Some software may not conform to this document but still be accessible to some users with disabilities. Conversely, some software may conform to this document but still be inaccessible to some users with disabilities. Please refer to the section on known limitations of this document.

3.1 Conformance model

The conformance model of this document has been designed to allow different types of user agents with different input and output capabilities to conform. At the same time, the model is designed so that:

• people reading claims can determine whether a conforming user agent is likely to meet their accessibility needs, and
• people can compare claims about different user agents with relative ease. Note: The checklist [UAAG10-CHECKLIST] may be used when evaluating a user agent for conformance.

The conformance model works as follows:

• A user agent conforms to this document by satisfying a set of requirements. Conformance requirements only come from the checkpoint statements. Each checkpoint statement includes one or more requirements.
• The "default" set of requirements for conformance consists of all the requirements of all of the checkpoints. A user agent conforms unconditionally to this document if it satisfies all of these requirements.
• Different user agents may conform to different sets of checkpoints. A user agent conforms conditionally if it satisfies any set of requirements that results from carrying out the four steps below. Since these steps may produce very different sets of checkpoints for different user agents, a valid conformance claim must indicate how the set of requirements chosen for the claim differs from the default set.

A user agent conforms conditionally if it satisfies any set of requirements that results from following these steps:

1. Choose a conformance level. Each conformance level corresponds to a set of checkpoints (and thus a set of requirements).
2. Remove the requirements associated with any unsupported content type labels. In order to conform conditionally, a user agent must satisfy the requirements of at least one content type label.
3. Remove the requirements of any checkpoints or parts of checkpoints that do not apply.
4. If the user agent does not implement a selection mechanism, remove the requirements of any checkpoints or parts of checkpoints associated with the selection label.
5. Add requirements associated with any supported input modality label. Note: In the default set of requirements, the only input device requirements relate to keyboard input.

Example of how to determine conformance requirements

The following example illustrates how to apply the above steps to determine which requirements must be satisfied for conformance, and what would be required as part of a well-formed conformance claim. This informative example does not illustrate a complete user agent evaluation.

Consider a user agent with these capabilities:

• it supports keyboard and pointing device input;
• it renders text (in color) and implements:
  • one audio format,
  • two image formats,
  • two other animation formats (besides video, which is considered an animation format in this document);
• it hands off video to be rendered by a plug-in;
• it doesn't support speech output;
• it implements a selection mechanism.

Step 1: Choose a conformance level.

The claimant wishes to conform at level Double-A. This establishes a set of requirements consisting of all of the requirements of all the priority 1 and 2 checkpoints.

Step 2: Remove the requirements associated with any unsupported content type labels.

The claimant wishes to claim conformance for the user agent's support of text, images, audio, and video. The claimant does not wish to claim conformance for other animation formats.

The following content type labels are therefore relevant: VisualText, ColorText, Image, Animation, Video, and Audio. This means that:

• the claimant must remove the set of requirements associated with the Speech content type label.
• the claimant must satisfy the requirements associated with the other content type labels.

Step 3: Remove the requirements of any checkpoints or parts of checkpoints that do not apply.

Consider checkpoint 4.4, for example, which is associated with both the Audio and Animation content type labels:

4.4 Slow multimedia. Allow the user to slow the presentation rate of audio and animations (including video and animated images). 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 the user agent allows the user to slow the visual track of a synchronized multimedia presentation to between 100% and 80% of its original speed, synchronize the visual and audio tracks. Below 80%, the user agent is not required to render the audio track. The user agent is not required to satisfy this checkpoint for audio and animations whose recognized role is to create a purely stylistic effect. [Priority 1]

Suppose that:

1. The claimant wishes to claim support for the two image formats, the one audio format, and the one video format;
2. The claimant does not wish to claim support for the other two animation formats (e.g., because the user agent doesn't satisfy the requirements of checkpoint 4.4 for those animation formats);
3. The user agent does not implement any synchronized multimedia formats.

The resulting applicable requirements from this checkpoint would be:

• For the audio format: Allow the user to slow the presentation rate of audio. For a prerecorded audio track including audio-only presentations, provide at least one setting between 75% and 80% of the original speed.
• For the video format: Allow the user to slow the presentation rate of video. For a visual track, provide at least one setting between 40% and 60% of the original speed.
• For the image formats: None, since the Image content type label does not include checkpoint checkpoint 4.4.
• Limitation of scope for any format: The user agent is not required to satisfy the requirements of this checkpoint for audio and animations whose recognized role is to create a purely stylistic effect.

The following requirements would not apply:

• When the user agent allows the user to slow the visual track of a synchronized multimedia presentation to between 100% and 80% of its original speed, synchronize the visual and audio tracks. Below 80%, the user agent is not required to render the audio track. Note: The relevant applicability provision is provision three: control of a content property that the subject cannot recognize. In this case, no format implemented by the user agent supports synchronized multimedia.

Step 4: Add requirements related to the selection.

In this example, since the user agent implements a selection mechanism, it must satisfy the requirements associated with the selection label.

Step 5: Add requirements associated with any supported input modality label.

In this example, the claimant does not wish to claim conformance for complete operation for pointing device or voice input, so no requirements are added.

Construct a well-formed conformance claim.

The following information is an excerpt of that required for a well-formed claim:

• Conformance level satisfied: Double-A
• Information about the subject. Both the "main" user agent and the plug-in used to support video must be identified in the claim (since the plug-in is the component used to satisfy the requirements for video).

The user agent does not conform unconditionally, therefore, the claim must also include the following information (excerpted from a complete claim):

• A general statement about lack of support for the Speech content type label: "This user agent does not support the requirements of the Speech content type label. "
• A specific statement about content type support for checkpoint 4.4: "This user agent satisfies the requirements of the Animation content type label for the audio format A and the video format V. It does not satisfy the Animation requirements for animation formats Y and Z."
• A specific statement about applicability for checkpoint 4.4: "The synchronized multimedia requirements of checkpoint checkpoint 4.4 do not apply because the user agent does not implement any formats that support synchronized multimedia."

3.2 Conformance levels

Each conformance level defines a set of requirements, based on priority.

• Conformance Level "A": the requirements of all Priority 1 checkpoints.
• Conformance Level "Double-A": the requirements of all Priority 1 and 2 checkpoints.
• Conformance Level "Triple-A": the requirements of all Priority 1, 2, and 3 checkpoints.

Note: Conformance levels are spelled out in text (e.g., "Double-A" rather than "AA") so they may be understood when rendered as speech.

3.3 Content type labels

Each content type label defines a set of requirements related to support for images, video, animations generally, visually displayed text (in color), and synthesized speech.

VisualText

This content type label refers to all of the requirements related to the visual rendering of text for the following checkpoints: 3.3, 4.1, and 4.2.

ColorText

This content type label refers to all of the requirements related to text foreground and background color for the following checkpoint: 10.4.

Image

This content type label refers to all of the requirements related to images (excluding animated images) for the following checkpoints: 3.1, 3.7, and 3.8. To conform, the user agent must implement at least one image format.

Animation

This content type label refers to all of the requirements related to animations (including video and animated images) for the following checkpoints: 3.2, 3.8, 4.4, 4.5, 4.7, and 4.8. To conform, the user agent must implement at least one animation format.

Video

This content type label refers to all of the requirements related to video for the following checkpoints: 2.5, 2.6, 3.2, and 3.8. To conform, the user agent must implement at least one video format.

Audio

This content type label refers to all of the requirements related to audio for the following checkpoints: 2.5, 2.6, 3.2, 3.8, 4.4, 4.5, 4.7, 4.8, 4.9, 4.10, and 4.11 To conform, the user agent must implement at least one audio format.

Speech

This content type label refers to all of the requirements related to synthesized speech for the following checkpoints: 4.12, 4.13, 4.14, 4.15, and 4.16. To conform, the user agent must support synthesized speech.

Note: Some of the labels above require implementation of at least one format (e.g., for images). This document does not require implementation of specific formats, (e.g., PNG [PNG] versus SVG [SVG] for images). However, please see the requirements of checkpoint 8.2.

3.4 Input modality labels

Each input modality label defines a set of requirements related to support for pointing device and voice input. Input device requirements in this document are either stated generically (e.g., "input configuration" requirements) or as keyboard-specific requirements (e.g., "keyboard API").

Pointer

This input modality label refers to all of the input device requirements of this document, applied to pointing device input. For keyboard-specific requirements, substitute "pointing device input" for "keyboard." The set of pointing device input requirements does not include the requirements of checkpoint 11.4.

Voice

This input modality label refers to all of the input device requirements of this document, applied to voice input. For keyboard-specific requirements, substitute "voice input" for "keyboard." The set of voice input requirements does not include the requirements of checkpoint 11.4.

Note: Developers are encouraged to design user agents that are at least partially operable through all three input modalities.

3.5 Selection label

This document does not require the user agent to implement a selection mechanism in order to conform. However, if the user agent does implement a selection mechanism, in order to conform it must satisfy the relevant portions of the following checkpoints: 6.5, 7.1, 9.4, 10.2, 10.3, and 5.4. The Selection label refers to the selection requirements of these checkpoints.

If a user agent does not implement a selection mechanism, then a well-formed claim must say so.

Note: This document does require implementation of both content focus and user interface focus; see checkpoint 9.1 and checkpoint 9.2.

3.6 Checkpoint applicability

A checkpoint (or part of a checkpoint) applies unless any one of the following conditions is met:

1. The checkpoint makes requirements for graphical user interfaces or graphical viewports and the subject of the claim only has audio or tactile user interfaces or viewports.
2. The checkpoint refers to a role of content (e.g., transcript, captions, associated conditional content, fee link, synchronization cue, client-side redirect, purpose of a table, etc.) that the subject of the claim cannot recognize because of how the content has been encoded in a particular format. For instance, HTML user agents can recognize "alt", OBJECT content, or NOFRAMES content as specified mechanisms for conditional content. HTML user agents are not expected to recognize that a nearby paragraph is a text equivalent for the image (though not marked up as such).
3. The checkpoint requires control of a content property that the subject cannot recognize because of how the content has been encoded in a particular format. Some examples of this include:
   • captioning information that is "burned" into a video presentation and cannot be recognized as captions in the presentation format;
   • streamed content that cannot be fast advanced or reversed,
   • information or relationships encoded in scripts in a manner that cannot be recognized. For instance, the requirements of checkpoint 3.3 would not apply for animation effects unrecognized in a script. Some input device behavior may be controlled by scripts in a manner that the user agent cannot recognize. For example, when the author uses event bubbling to dispatch events, the user agent is not likely to recognize the full set of elements that may receive those events; the user agent is expected to recognize which element has the explicitly associated event handler.

3.7 Well-formed conformance claims

A claim is well-formed if meets the following conditions.

Condition 1: The claim must include the following information:

1. The date of the claim.
2. The guidelines title/version: "User Agent Accessibility Guidelines 1.0".
3. The URI of the guidelines: http://www.w3.org/WAI/UA/WD-UAAG10-20010525.
4. The conformance level satisfied: "A", "Double-A", or "Triple-A".
5. Information about the subject. The subject of the claim may consist of one or more software components (e.g., a browser plus a multimedia player plus a plug-in). For each component, the claim must include the following:
   • The user agent name and version information (version number, minor release number, and any required patches or updates). The claim must also include the vendor name if it is required to identify the user agent.
   • The operating environment (e.g., operating system) name and version number.

Condition 2: The claim must include the following information if the user agent conforms conditionally:

1. Content type labels. Content type labels are used in assertions that the subject either (1) does not satisfy the requirements associated with the label (e.g., for a specific checkpoint, for any checkpoint, etc.), or (2) does satisfy the requirements associated with the label (e.g., for a particular format when satisfying the requirements of a checkpoint). In order to conform conditionally, a user agent must satisfy the requirements of at least one content type label.
2. Input modality labels. Each input modality label ("Pointer" or "Voice") is an assertion that the user agent satisfies the requirements associated with the label.
3. Selection label. If the user agent does not implement a selection mechanism, the claim must say so.
4. A list of requirements (checkpoints or portions of checkpoints) that the claim asserts do not apply.

Condition 3: If the claim is on the Web, it must conform to the "Web Content Accessibility Guidelines 1.0" [WCAG10], level A.

A well-formed claim should also include the following information:

• Information about which specifications have been implemented to satisfy the requirements of the document (e.g., those of guideline 6 and guideline 8).
• Rationale for any requirements that do not apply.

This specification imposes no restrictions on the format used to make a well-formed claim. For instance, the claim may be marked up using HTML (see sample claim), or expressed in the Resource Description Framework (RDF) [RDF10].

3.8 Validity of a claim

A conformance claim is valid if the following conditions are met:

1. The claim is well-formed.
2. It is verified that the user agent satisfies the default set of requirements, in addition to (or except) those requirements added (or exempted) by the allowable mechanisms: conformance levels, content type labels, input modality labels, and applicability.

It is not currently possible to validate a claim entirely automatically.

Note: The subject of the claim may consist of more than one software component, and taken together they must satisfy all requirements that are not excluded through the claim. This includes assistive technologies and operating environment features that are part of a claim. Some components may not have to satisfy some requirements as long as the subject as a whole satisfies them. For instance, a particular component of the subject may not have to conform to the DOM APIs required by guideline 6 as long as the subject of the claim as a whole makes all content available through those APIs.

Note: Ideally, the default user agent installation procedure should provide and install all components that are part of a conformance claim. This is because, the more software components the user must install in order to construct a conforming user agent, the higher the risk of failure. Failure may be due to inaccessible mechanisms for downloading and installing plug-ins, or lack of installation access privileges for a computer in a public space, etc.

Responsibility for claims

This specification imposes no restrictions about:

• who may make a claim (e.g., vendors about their own user agents, third parties about those user agents, journalists about user agents, etc.), or
• where claims may be published (e.g., on the Web or in paper documentation).

Claimants (or relevant assuring parties) are solely responsible for the validity of their claims, keeping claims up to date, and proper use of the conformance icons. As of the publication of this document, W3C does not act as an assuring party, but it may do so in the future, or it may establish recommendations for assuring parties.

Claimants are expected to modify or retract a claim if it may be demonstrated that the claim is not valid. Claimants are encouraged to claim conformance to the most recent User Agent Accessibility Guidelines Recommendation available.

Conformance icons

As part of a conformance claim, people may use a conformance icon (or, "conformance logo") on a Web site, on user agent packaging, in documentation, etc. Each conformance icon (chosen according to the appropriate conformance level) used on the Web must link to the W3C explanation of the icon. The appearance of a conformance icon does not imply that W3C has reviewed or validated the claim. An icon must be accompanied by a well-formed claim.

Draft Note: In the event this document becomes a W3C Recommendation this document will link to the W3C Web site for additional information about the icons and how to use them.

3.9 Additional conformance topics

The following sections describe additional conformance requirements and exemptions.

Conformance and implementing specifications

User agents may conform (both unconditionally and conditionally) by satisfying the the specification requirements of this document for some, but not all, implemented specifications and APIs. For example, a developer may implement ten image formats but only wish to claim "Image" conformance for three of them.

In particular, the following requirements may be satisfied for some but not all implemented specifications:

• requirements associated with a content type label;
• the API requirements of checkpoint checkpoint 6.3, checkpoint 6.4, and checkpoint 6.5.
• the rendering requirements of checkpoints 2.1 and 2.2;
• the format requirements of checkpoints 8.1 and 8.2.

Requirements for content, user agent features, or both

Each checkpoint definition indicates whether the requirements of the checkpoint must be satisfied by the subject of the claim for:

1. content only, i.e., the document object.
2. user agent features only, i.e., everything besides the document object (e.g., components of the user agent user interface, the user agent documentation, and the user interface focus).
3. both content and user agent features.

The user agent may satisfy a "content only" requirement with a mechanism that also involves user agent features. For instance, to satisfy checkpoint 4.9, the user agent may provide a single control for all volume (including content and user interface features). Similarly, to satisfy checkpoint 3.3, the user agent may offer a single configuration that turns off blinking in both content and the user interface.

The user agent may satisfy the configuration requirements of this document through configuration files (e.g., profiles, initialization files, etc.). For instance, style sheets might be used as a mechanism to satisfy the highlight and configuration requirements of checkpoints 10.2 and 10.4. Any functionality that is configurable through a configuration file should also be configurable through the user agent user interface. Furthermore, if configuration files may be edited by hand, the user agent documentation should explain the configuration file format.

Note. Depending on the checkpoint, content focus and selection requirements may have any of the three labels. Content focus and selection are "state variables" that straddle both worlds of content and user agent user interface.

Requirements satisfied through user interface or API

The requirements of guideline 6 must be satisfied by implementing APIs.

The requirements of the other guidelines must be satisfied by at least one mechanism other than an API. These requirements are not meant to be satisfied by assistive technologies (unless those technologies are part of a conformance claim). For example, checkpoint 9.3 involves navigation that must be possible through the user interface, not just via an API.

Use of operating environment features as part of conformance

To satisfy the requirements of this document, developers are encouraged to adopt operating environment conventions and features that benefit accessibility. When an operating environment feature (e.g., the operating system's audio control feature, including its user interface) is adopted to satisfy the requirements of this document, it is part of the subject of the claim.

Developers may provide access through the user agent's user interface to operating environment features adopted to satisfy the requirements of this document. For example, if the user agent adopts the operating system's audio control feature to satisfy checkpoint 4.9, the user agent may (but is not required to) include those controls in its own user interface.

Restricted functionality and conformance

User agents do not conform to this document on a per-resource basis; claims are not as specific as "the user agent conforms for this particular Web page." A user agent conforms if it satisfies the requirements of this document for most general-purpose content, in ordinary operating conditions.

In some cases, an author may wish to limit the user agent's functionality for specific reasons, such as to protect intellectual property rights, for security reasons, or to provide a read-only view (allowing no user interaction). Content that limits the functionality of the user agent in some cases does not automatically invalidate a conformance claim. A valid conformance claim remains valid as long as the user agent is capable of satisfying the requirements of the document (i.e., the functionalities have been implemented), and does so for most general-purpose content.

Note: 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.