W3C published the Web Content
Accessibility Guidelines 1.0 (WCAG 1.0) as a Recommendation in May 1999.
This Working Draft for version 2.0 builds on WCAG 1.0. It has the same aim:
to explain how to make Web content accessible to people with disabilities and
to define target levels of accessibility. Incorporating feedback on WCAG 1.0,
this Working Draft of version 2.0 focuses on checkpoints. It attempts to
apply checkpoints to a wider range of technologies and to use wording that
may be understood by a more varied audience.
This document is prepared by the Web
Content Accessibility Guidelines Working Group (WCAG WG) to show how more
generalized (less HTML-specific) WCAG checkpoints might
read. This draft is not yet based on consensus of the WCAG Working Group nor
has it gone through W3C process. This Working Draft in no way supersedes WCAG 1.0.
Please refer to "Issue Tracking for WCAG
2.0 Working Draft" for a list of open issues related to this Working
Draft. The "History of Changes
to WCAG 2.0 Working Drafts" is also available.
This is a draft document and may be updated, replaced, or obsoleted by
other documents at any time. It is inappropriate to use W3C Working Drafts as
reference material or to cite them as other than "work in progress". A list
of current W3C Recommendations and other
technical documents is available.
The Working Group welcomes comments on this document at w3c-wai-gl@w3.org. The archives for this
list are publicly available.
Patent disclosures relevant to this specification may be found on the WCAG
Working Group's patent
disclosure page in conformance with W3C policy.
This document has been produced as part of the W3C Web Accessibility Initiative (WAI). The
goals of the WCAG WG are discussed in the Working Group
charter. The WCAG WG is part of the WAI Technical
Activity.
This document outlines design principles for creating accessible Web
content. When these principles are ignored, individuals with disabilities may
not be able to access the content at all, or they may be able to do so only
with great difficulty. When these principles are employed, they also make Web
content accessible to a variety of Web-enabled devices, such as phones,
handheld devices, kiosks, network appliances, etc. By making content
accessible to a variety of devices, that content will also be accessible to
people in a variety of situations.
The design principles in this document represent broad concepts that apply
to all Web-based content. They are not specific to HTML, XML, or any other
technology. This approach was taken so that the design principles could be
applied to a variety of situations and technologies, including those that do
not yet exist.
In order to facilitate understanding of the guidelines and to help people
focus in on just the parts they need, the guidelines are presented as a set
of interrelated documents. There are basically 3 layers to the guidelines
information.
The top layer is titled "Web Content Accessibility Guidelines
2.0". It is the document you are currently reading. This document
provides:
- An introduction
- The 5 major Guidelines for accessibility (Perceivable, Operable,
Navigable, Understandable and Robust).
- The (non-technology-specific) checkpoints for each guideline (21 in
total).
- Success criteria (normative), and definitions, benefits and examples
(all non-normative) for each checkpoint
- An appendix containing definitions, references and other support
information.
In addition to the general guidelines, there will be a series of
technology-specific checklist documents. These documents will provide
information on what is required when using different technologies in order to
meet the WCAG 2.0 Working Draft access guidelines.
Reviewer's Note: These checklists do not
yet exist. At the present time the checklists are expected to be
non-normative, though no formal decision has been made.
The Techniques Documents will include code examples, screen shots, and
other information specific to a technology. These documents will be
non-normative. They will contain different strategies for meeting the
requirements as well as the current preferred approaches where they exist.
Examples include:
- Hypertext Markup Language (HTML) and Extensible Hypertext Markup
Language (XHTML_) Techniques
- Cascading Style Sheets (CSS) Techniques
- Server-side scripting Techniques
- Client-side scripting Techniques
- Scalable Vector Graphics (SVG) Techniques
- Synchronized Multimedia Integration Language (SMIL) Techniques
- Extensible Markup Language (XML) Techniques
(These will become active links as the corresponding working drafts
are published)
These guidelines have been written to meet the needs of many different
audiences from policy makers, to managers, to those who create Web content,
to those who code the pages. Every attempt has been made to make the document
as readable and usable as possible while still retaining the accuracy and
clarity needed in a technical specification. For first time users, the work
of the Education and Outreach Working
Group of the Web Accessibility Initiative is highly recommended.
The guidelines cover a wide range of issues and recommendations for making
Web content more accessible. They include recommendations to make pages
accessible and usable by people with a full range of disabilities. In
general, the guidelines do not include standard usability recommendations
except where they have specific ramifications for accessibility beyond
standard usability impacts.
This WCAG 2.0 Working Draft does not assign priorities to checkpoints, as
did WCAG 1.0. Instead, each of the checkpoints has levels of implementation
listed for it. There are 3 levels labeled "Minimum", "Level 2", and "Level
3". The main WCAG 2.0 Working Draft document does not include
technology-specific implementation requirements or techniques, but it does
include links to technology-specific requirements as well as
technology-specific examples and techniques.
This Working Draft of WCAG 2.0 is a follow-on and evolution of WCAG 1.0
and reflects feedback received since the publication of WCAG 1.0 in May 1999.
Although the same approaches to accessibility are followed in 1.0 and 2.0,
the organization and structure have been improved significantly.
The Web Content Accessibility Guidelines Working Group is working
carefully to enable organizations and individuals that are currently using
WCAG 1.0 (which remains stable and referenceable at this time) to ensure that
they will eventually be able to make a smooth transition to WCAG 2.0. To
understand how this eventual transition would be facilitated, please refer to
the (draft) Checkpoint
Mapping Between WCAG 1.0 and the WCAG 2.0 Working Draft for more detail
on current correspondences.
Reviewer's Note: As we publish this
Public Working Draft of WCAG 2.0, the WCAG WG is in the midst of addressing a
variety of issues with conformance. This section outlines the conformance
structure used throughout this document and advises the reader that the WCAG
WG has discovered a variety of issues with this scheme. The issues are
outlined for the reader's consideration. Feedback, comments, and proposals
are encouraged. Further information about current proposals and recent discussion is available.
This draft uses the following three levels of conformance:
-
Minimum Level
- includes success criteria for the checkpoint that address key
problems and are applicable across the broad range of Web content and
sites. Conformance at this level will substantially overcome the
barriers for many people with disabilities, but there will be people
with disabilities who will still not be able to access the content. No
claim of conformance can be made unless the minimum level of
conformance is achieved for all checkpoints.
-
Level 2
- includes additional success criteria that increase the accessibility
of Web content, but that are more difficult to implement on Web content
in general or on specific types of content.
-
Level 3
- represents the highest level of conformance in WCAG 2.0. It includes
success criteria that may be very difficult as well as criteria that
may not be possible at all for some types of content or some Web
architectures.
If the above conformance levels are used, the rules regarding conformance
claims would be:
- No conformance claim of any type may be made unless all MINIMUM Level
success criteria have been met for all checkpoints in WCAG 2.0.
- If all of the checkpoints have been met at the MINIMUM Level, but only
some of the criteria for Level 2 have been met, then a conformance claim
at "LEVEL 1+" can be made.
- If all success criteria (for all checkpoints) are met at the MINIMUM
Level and Level 2, then a claim conformance at "Level 2" can be made.
- If all of the success criteria for (for all checkpoints) are met at the
MINIMUM and Level 2, as well as some, but not all of the criteria for
Level 3, then a conformance claim can be made at "Level 2+".
- If all success criteria for all Levels have been met, then a
conformance claim at "Level 3" can be made.
For conformance claims of Level 1+ and Level 2+, it is recommended (but
not required) that sites report specifically which criteria they have met
within each of the guidelines and checkpoints. WCAG 2.0 Techniques documents
will provide examples that show how to report which success criteria have
been met from Levels 2 and 3.
All conformance claims must include (at minimum):
- The version of the guidelines to which a conformance claim is made and
the URI of the guidelines document.
- The scope of the conformance claim. The scope describes which parts of
a site or application are included in the claim.
Reviewer's Note:
Should exclusions be allowed for certain types of
content, such as third-party or copyrighted material that is being
reprinted? How does one define scope? Is it an end-to-end process that
the user should be able to complete? Is it a path through accessible
content?
- The level at which conformance is claimed.
- The date the conformance claim was made.
Sites that currently conform to WCAG 1.0 that want to shift towards WCAG
2.0 will want to capitalize on past accessibility efforts. A qualified
conformance statement could allow them this flexibility. For example, a
conformance claim might include the following statement, "Materials created
or modified before 24 April 2003 conform to WCAG 1.0. Materials created or
modified on or after 24 April 2003 conform to WCAG 2.0."
Reviewer's Note: In some instances,
the WCAG 2.0 Working Draft may be easier to conform to than the WCAG 1.0
Recommendation. However, the WCAG 2.0 Working Draft requires a minimum level
of conformance to each checkpoint and this may make some parts of WCAG 2.0
harder to conform to than WCAG 1.0. For example, in WCAG 1.0 checkpoints
related to providing navigation mechanisms are priority 2 and 3, while in
this WCAG 2.0 Working Draft there are several minimum level success criteria
for navigation mechanisms. This might be resolved by merging some checkpoints
and moving some of the success criteria to the Second Level rather than the
Minimum.
The WCAG WG is committed to making WCAG 2.0
backwards compatible with WCAG 1.0.
Reviewer's Note: As the WCAG WG has discussed conformance, there has been
concern about requiring changes in style and content to meet accessibility
requirements. This section summarizes these issues.
The primary strategy to improve accessibility has been to supplement
content with additional information. For example, text equivalents and
structural markup enable a user agent or assistive technology to make the
content accessible to the user. Some of the current checkpoints require
authors to change the manner in which their primary content is expressed or
presented. For example, checkpoint 1.4 (emphasize structure through
presentation), checkpoint 3.1 (provide structure), 4.1 (write clearly) and
4.2 (supplement text with illustrations) all have requirements at the minimum
level. There are two issues with altering the primary content rather than
supplementing it:
- it potentially limits the author's freedom of expression,
- it is not appropriate or permissible in some circumstances, e.g., in
the case of legal documents, and historical, artistic, and literary
works.
Should minimum level success criteria that impose constraints on the
author's means of expression be shifted to level 2? We have discussed a
variety of potential future technologies (e.g., metadata). However, those
tools are not widely deployed and the schema still in development. How should
we address the tension between solving current problems without constraining
the author's freedom of expression? How do we address the opportunities that
emerging technologies such as metadata will provide? Can we achieve some of
this with semantic markup and next generation assistive technologies?
Recent proposals significantly redefine the three levels. With the
proposed priority schemes, success criteria that require changes in content
are no longer in the minimum level. However, the following issues remain to
be addressed:
- Is the minimum set limited to those success criteria that can be
accomplished via markup or code?
- Can we require anything in the minimum set that might impact someone's
freedom of expression?
- Is the minimum set tied to what is possible today while other levels
are more open to what will be possible in the future?
- Is the minimum set only those success criteria that can be tested with
an automatic tool?
- Is the minimum set not only success criteria that have the greatest
impact on accessibility but also those that are most feasible to do
today?
- Do the different groupings represent a hierarchical relationship? If
not, is "group" or "category" a more appropriate term than "level?"
- Will we have three priority levels or will they collapse into two?
The overall goal is to create Web content that is perceivable, operable,
navigable, and understandable by the broadest possible range of users and
compatible with their wide range of assistive technologies, now and in the
future.
- Perceivable. Ensure that all content can be presented
in form(s) that can be perceived by any user - except those aspects of
the content that cannot be expressed in words.
- Operable. Ensure that the interface elements in the
content are operable by any user.
- Navigable. Facilitate content orientation and
navigation
- Understandable. Make it as easy as possible to
understand the content and controls.
- Robust. Use Web technologies that maximize the ability
of the content to work with current and future accessibility technologies
and user agents.
Accessible Web content benefits a variety of people, not just people with
disabilities. In the physical world, ramps are used by bicycles, people
pushing strollers, and people in wheelchairs. Similarly, accessible Web
content is usable by a variety of people with and without disabilities. For
example, people who are temporarily operating under constrained conditions
like operating in a noisy environment or driving their car where their eyes
are busy. Likewise, a search engine can find a famous quote in a movie if the
movie is captioned.
Note: These principles apply only to Web content
presented to a human reader. A structured database or metadata collection
where the data is intended for use by another machine and thus requires no
interface lies outside the scope of these guidelines.
Here are a few scenarios, by no means an exhaustive list of the variations
and types of disabilities and needs:
- Someone who cannot hear will want to see the information normally
presented via sound.
- Someone who cannot see will want to hear or read through braille
information that is usually presented visually.
- Someone who does not have the strength to move quickly or easily will
want to use as little movement as possible and have as much time as they
need when operating Web interfaces.
- Someone who does not read well may want to hear the information read
aloud.
If Web content employs the design principles described in this document,
then users should be able to access the content using adaptive strategies and
assistive technologies. A screen reader is an example of an assistive
technology that reads the page aloud. There are many other tools people with
disabilities employ to make use of Web content. For more in-depth scenarios
of people with disabilities using accessible and inaccessible Web content,
please read "How
People with Disabilities Use the Web".
These guidelines provide the basic requirements for designing accessible
Web content. This document is not designed to provide the background needed
to learn about accessible Web design in a thorough or effective manner for
those interested in learning. Readers are therefore referred to the Education and Outreach Working Group of
the Web Accessibility Initiative.
Essential to any access to Web content is the ability of the user to have
the information presented in a form which they can perceive.
The checkpoints under this guideline impact individuals with sensory
disabilities by allowing the information to be transformed and presented in a
form which they can perceive. They also impact individuals with cognitive and
language disabilities by ensuring that the information is in a format that
can be perceived by mainstream and assistive technologies which can read the
content to them as well as (increasingly over time) transform and present it
in a form which is easier for them to understand.
- non-text content that can be expressed in words has a text-equivalent
explicitly associated with it.
- non-text content that can not be expressed in words has a descriptive
label provided as its text-equivalent.
- The text equivalent should fulfill the same function as the author
intended for the non-text content (i.e. it presents all of the
intended information and/or achieves the same function of the
non-text content).
- the text-equivalent has been
reviewed and is believed to fulfill the same function as the author
intended for the non-text content (i.e. it presents all of the intended
information and/or achieves the same function of the non-text
content)
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
- an audio description is provided of all significant visual information in scenes, actions and events that cannot be perceived from the sound track alone.
- Note: When adding audio description to existing materials, the amount of information conveyed through audio description is constrained by the amount of space available in the existing audio track. It may also be impossible or inappropriate to freeze the audio/visual program to insert additional audio description.
- all significant dialogue and sounds are captioned
exception: if the Web content is real-time and audio-only and not time-sensitive and not interactive a transcript or other non-audio equivalent is sufficient.
- descriptions and captions are synchronized with the events they represent.
-
if the Web content is real-time video
with audio, real-time captions are provided unless the content:
-
is a music program that is primarily non-vocal
-
If the Web content is real-time non-interactive video (e.g., a Webcam of ambient conditions), either provide an equivalent that conforms to checkpoint 1.1 (e.g., an ongoing update of weather conditions) or link to an equivalent that conforms to checkpoint 1.1 (e.g., a link to a weather Web site).
- if a pure audio or pure video presentation requires a user to respond interactively at specific times in the presentation, then a time-synchronized equivalent (audio, visual or text) presentation is provided.
exception:
if content is rebroadcast from another medium or resource that complies to broadcast requirements for accessibility (independent of these guidelines), the rebroadcast satisfies the checkpoint if it complies with the other guidelines.
- the audio description has been reviewed and is believed to include all significant visual information in scenes, actions and events (that can't be perceived from the sound track) to the extent possible given the constraints posed by the existing audio track (and constraints on freezing the audio/visual program to insert additional auditory description).
- a text document that merges all audio descriptions and captions into a collated script (that provides dialog, important sounds and important visual information in a single text document) is provided.
- captions and audio descriptions are provided for all live broadcasts
which provide the same information.
- The presentation does not require the user to read captions and the visual presentation simultaneously in order to understand the content.
- (presently no additional criteria for this level.)
- any information that is conveyed through presentation formatting is
also provided in either text or structure.
- the following can be derived programmatically (i.e. through assistive
technology compatible markup or data model) from the content without
interpreting presentation.
- any hierarchical elements and relationships, such as headings,
paragraphs and lists
- any non-hierarchical relationships between elements such as
cross-references and linkages, associations between labels and
controls, associations between cells and their headers, etc.
- any emphasis
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
- the structural elements present have a different visual appearance or
auditory characteristic than the other structural elements.
- the structural emphases are chosen to be distinct for different major
display types (e.g. black and white, small display, mono audio
playback).
- content is constructed such that users can control the presentation of
the structural elements.
- alternate presentation formats are available to vary the emphasis of
the structure.
Note: Because the form and origin (including letters,
art, historical documents, etc) of content varies so greatly, specific
criteria for the type and amount of emphasis to be provided can not be
standardized. Objective success criteria cannot therefore be formulated that
would apply across media and documents. Advisory recommendations are however
listed below to provide guidance in emphasizing the structure of content. See
also the techniques documents for the different technologies.
- for visual presentations, use font variations, styles, size and white
space to emphasize structure.
- use color and graphics to emphasize structure.
- for auditory presentations, use different voice characteristics
and/sounds for major headings, sections and other structural
elements.
- if content is targeted for a specific user group and the presentation
of the structured content is not salient enough to meet the needs of your
audience, use additional graphics, colors, sounds, and other aspects of
presentation to emphasize the structure.
- provide a table of contents or navigation map of the document.
Note: Ensure that the structural and semantic
distinctions are provided in the markup or data model. Refer to checkpoint
1.3.
- text content that is presented over a background image or pattern is
implemented using mechanisms that allow the user to display the text without the background image or pattern.
- when text content is presented over a background image or pattern, the text
is easily readable when the page is viewed in 256 grayscale.
- text content is not presented over a background image or pattern OR the
text is easily readable when the page is viewed in black and white (no grayscale).
- audio content does not contain background sounds OR the background sounds
are at least 20 db lower than the foreground audio content.
- text content is not presented over a background image or color OR the
colors used for the text and background or background image pass the
following test (from Techniques For Accessibility Evaluation And Repair
Tools, dated April 26, 2000):
- Two colors provide good color visibility if the brightness difference
and the color difference between the two colors are greater than a set
range.
- Color brightness is determined by the following formula:
((Red value X 299) + (Green value X 587) + (Blue value X 114)) / 1000
Note: This algorithm is taken from a formula for converting RGB values
to YIQ values. This brightness value gives a perceived brightness for a
color.
- Color difference is determined by the following formula:
(maximum (Red value 1, Red value 2) - minimum (Red value 1, Red value
2)) + (maximum (Green value 1, Green value 2) - minimum (Green value 1,
Green value 2)) + (maximum (Blue value 1, Blue value 2) - minimum (Blue
value 1, Blue value 2))
- The range for color brightness difference is 125. The range for color
difference is 500.
Reviewer's Note: There is some question about whether this algorithm yields content with sufficient contrast. The working group is currently in the process of researching a number of methods for determining sufficient contrast and color visibility.
- (presently no additional criteria for this level.)
- text in the content is provided in Unicode or sufficient information is
provided so that it will be automatically mapped back to Unicode.
- passages or fragments of text occurring within the content that are
written in a language other than the primary natural language of the
content as a whole, are identified, including specification of the
language of the passage or fragment.
- abbreviations and acronyms are clearly identified where they occur.
(See also checkpoint 4.3.)
- symbols such as diacritic marks that are found in standard usage of the
natural language of the content, and necessary for unambiguous
interpretation of words, are present or another standard mechanism for
disambiguation is provided.
- the primary natural language of the content is identified at the page
level.
- (presently no additional criteria for this level.)
Note: This checkpoint addresses the need for authors to
provide sufficient information so that text can be identified correctly by
technologies used to render the text (e.g. voice synthesizers) so that the
words can be accurately produced and perceived. This checkpoint does not deal
with providing definitions or expanded text for words, abbreviations, foreign
phrases etc. These are covered under checkpoint 4.3 since they deal with
understanding of the content.
Also essential to accessibility is the ability to be able to operate all
of the interface elements on the page without requiring the use of specific
input devices.
This guideline impacts individuals who are blind, individuals who have low
vision and have trouble with eye-hand coordination input devices, individuals
with physical disabilities who cannot handle direct pointing devices
accurately, and individuals with language and learning disabilities who would
like to use speech input now or in the future.
- all of the functionality of the content where the functionality or
its outcome can be expressed concisely in words is operable at a minimum
through a keyboard or keyboard interface.
- Note: refer to checkpoint 5.3 for information
regarding user agent support.
- wherever a choice between event handlers is available and supported,
the more abstract event is used.
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
- at least one of the following is true for each time limit:
- the user is allowed to deactivate the time limits,
- or the user is allowed to adjust the time limit over a wide range
which is at least 10 times the average user's preference,
- or the user is warned before time expires and given at least 10
seconds to extend the time limit,
- or the time limit is due to a real-time event (e.g. auction) and no
alternative to the time limit is possible,
- or the time limit is part of a competitive activity where timing is
an essential part of the activity (e.g. competitive gaming or time
based testing).
- (presently no additional criteria for this level.)
- activities are designed so that time limits are not an essential part
of the activity (e.g. competition, testing, etc. are not time based).
- (presently no additional criteria for this level.)
- At least one of the following is true:
- content was not designed to flicker (or flash) in the range of 3 to
49 Hz.
-
Reviewer's Note: We would
like to include a criteria here which would state that a test that
was conducted and the pages passed. No test or tool exists yet
though. We're looking into how such a test and/or tool might be
designed.
- if flicker is unavoidable, the user is warned of the flicker before
they go to the page, and as close a version of the content as is
possible without flicker is provided.
- animation or other content does
not visibly or purposely flicker between 3 and 49 Hz.
- content that might create a
problem has been tested [using XYZ tool]; only pages with unavoidable
flicker remain and appropriate warnings along with a close alternative
presentation have been provided for these pages.
- (tougher test - that would make pages pass with even slower equip.
Equip might be old or just slow for other reasons)
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
Reviewer's Note: Trace is currently in
the process of exploring an automated flicker testing tool.
Key to effective use of Web content is the ability to obtain and keep one's and the ability to efficiently move about the site, document or application.
- the following minimum structure elements are present.
- titles on major sections of long documents
- paragraphs
- the content has been reviewed, taking into account the
additional ideas listed below, and is believed to contain
as much
structure as is possible and appropriate
- information is provided that would allow an assistive technology to
determine at least one logical, linear reading order
- diagrams are constructed in a fashion so that they have structure that
can be accessed by the user.
Note: Because the form and origin of content (including
letters, poetry, historical documents, etc.) varies so greatly, specific
criteria for the type and amount of structure to be put into content can not
be standardized. Objective success criteria cannot therefore be formulated
that would apply across media and documents. Advisory recommendations are,
however, listed below to provide guidance in adding key structural elements
into the content. See also the techniques documents for the different
technologies.
- break up text into logical paragraphs.
- provide hierarchical sections and titles, particularly for longer
documents
- reveal important non-hierarchical relationships, such as
cross-references, or the correspondence between header and data cells in
a table, so that they are represented unambiguously in the markup or data
model.
- divide very large works into sections and or chapters with logical
labels.
- others?
- sites that have more than two layers have at least one other method for
exploration besides using the links on the home page. (A home page and
one layer of pages linked off of it would be two layers)
- a link to the alternate exploration method(s) is provided on the home
page.
- sites that have documents that span multiple files either provide the
documents as a single file or provide a search function which would allow
the user to search for a word across only the files that make up that
document.
- large documents (greater than 50,000 words) include multiple mechanisms
for navigation such as a hyperlinked table of contents, internal
hyperlinks, an ability to collapse by headers, etc.
- (presently no additional criteria for this level.)
- key orientation and navigational elements are generally found in one or
two locations or their locations are otherwise predictable.
- the content has been reviewed, taking into account the
additional ideas listed below, and it has been concluded
that key
orientation and navigational
elements are generally found in one or two locations, or their locations
are otherwise predictable
- (presently no additional criteria for this level.)
- place navigation bars in a consistent location whenever possible
- similar layout for user interface components should be used for
sections or whole site,
- similar user interface components should be labeled with similar
terminology
- use headers consistently
- use templates for consistent presentation of sections or whole site
- pages with similar function should have similar appearance and
layout
- where inconsistent or unpredictable responses are essential to the
function of the content (e.g. mystery games, adventure games, tests,
etc.) the user is warned in advance of encountering them.
- wherever there are extreme changes in context, one of the following is
true:
- an easy to find setting, that persists for the site visit, is
provided for the user to deactivate processes or features that cause
extreme changes in context or
- extreme changes in context are identified before they occur so the
user can determine if they wish to proceed or so they can be prepared
for the change
- the content has been reviewed, and it has been found that where
inconsistent or unpredictable responses
are essential to its function (e.g. mystery games,
adventure games, tests, etc.), the user is warned in advance of
encountering them
- (presently no additional criteria for this level.)
- controls that look or sound the same should be designed to act the
same,
- conventions likely to be familiar to the user should be followed,
- unusual user interface features or behaviors that are likely to confuse
the first-time user should be described to the user before they are
encountered.
- if an error is detected, feedback is provided to the user identifying
the error.
- the content has been reviewed
and is believed to have incorporated error prevention and recovery
methods that are considered to be effective and appropriate
- where possible, the user is allowed to select from a list of options as
well as to generate input text directly
- errors are identified specifically and suggestions for correction are
provided where possible
- checks for misspelled words are applied and correct spellings are
suggested when text entry is required.
- where consequences are significant and time-response is not important,
one of the following is true
- actions are reversible where possible
- where not reversible, actions are checked for errors in
advance.
- where not reversible, and not checkable, a confirmation is asked
before acceptance
- (presently no additional criteria for this level.)
To help people understand the information you are presenting, consider the
various ways that people learn. Keep in mind the variety of backgrounds and
experiences people will bring to your site. Using language, illustrations,
and concepts that they are likely to know, highlighting the differences and
similarities between concepts, and providing explanations for unusual terms
can all facilitate understanding.
This checkpoint lists ideas to help you review content for clarity.
Plain language specialists around the world promote many of these ideas.
The following items are not presented as success criteria, however, or
as an attempt to impose editorial style. Rather, they are elements to
consider as you review writing. They reflect the idea that accessibility
begins with understanding.
Reviewer's Note: Since there has been concern about requirements at the minimum level that would require content to be presented in a particular way, this checkpoint has been worded in a way that requires authors to "consider" a list of criteria and review their content with that list in mind. Is this difference clear in comparison to other checkpoints?
- familiarity of terms and language structure
- reasonableness of length and complexity of sentences
- coherence of paragraphs (and sensibility in length)
- clarity of headings and linked text when read out of context
- accuracy and uniqueness of page titles
- care in the use of all-capital letters where normal sentence case
might increase comprehension
- use of sentence structures that increase understanding
- such as active voice in languages where this form helps convey
information
- length of noun phrases
- strings of no more than three or four nouns are easiest to understand
- clarity of reference with pronouns and anaphoric expressions (these
refer back to something already said in the text)
- example of potential ambiguity: "Scientists study monkeys. They eat
bananas."
- correct use of conjunction forms and adverbs to make explicit the
relationship between phrases or parts of the text
- such as "and," "but," "furthermore," "not only"
- complexity of verb tenses
- do the tenses used in a document seem overly complicated?
- intelligibility of verb phrases
- familiarity of idioms or slang
- logic in the order and flow of information
- consequences of ambiguity or abstraction
- improved readability of vertical lists might offer in place of long paragraphs of information
- use of summaries to aid understanding
- thoroughness in the explanation of instructions or required actions
- consistency in the use of names and labels
- clarity where the document:
- addresses users
- explains choices and options
- labels options to get more information
- instructs users how to modify selections in critical functions (such
as how to delete an item from a shopping cart)
- application of:
- proper markup to highlight key information
- goal-action structure for menu prompts
- default settings (and the ease in re-establishing them)
- two-step "select and confirm" processes to reduce accidental
selections for critical functions
- calculation assistance to reduce the need to calculate
- new material is tested with potential users for ease of accessibility
- a controlled language is used
- support is given for conversion into symbolic languages
- authors have included non-text content to supplement text for key pages
or sections of the site where they felt it was appropriate.
- the content has been reviewed and it is believed that text has been supplemented with non-text content to the
extent deemed appropriate by the author
- non-text content has
been added to the site for key pages or sections specifically to make the
site more understandable by users who cannot understand the text only
version of the site.
- (presently no additional criteria for this level.)
Note: Supplementing text with non-text (e.g. graphics,
sound, smell, etc) is useful for all users. However there are no clear
guidelines as it relates to disability. Specific objective criteria that
could be applied across all types of content are therefore not possible.
Advisory recommendations are, however, listed below to provide guidance in
this area. See also the techniques documents for the different
technologies.
Reviewer's Note: Do we have any items to
add here or do we just include examples below?
- acronyms and abbreviations are defined the first time they appear.
- the content has been reviewed, taking into account the
additional ideas listed below, and it is believed that
complex, abbreviated or unfamiliar information has been annotated appropriately
- (presently no additional criteria for this level.)
- provide a definition or link (with the first occurrence) of phrases,
words, acronyms, and abbreviations specific to a particular
community.
- provide a summary for relationships that may not be obvious from
analyzing the structure of a table but that may be apparent in a visual
rendering of the table.
- if contracted forms of words are used such that they are ambiguous,
provide semantic markup to make words unique and interpretable.
- for markup, except where the site has documented that a specification
was violated for backward compatibility, the markup has passed validity
tests of the language (whether it be conforming to a schema, Document
Type Definition (DTD), or other tests described in the specification),
structural elements and attributes are used as defined in the
specification, accessibility features are used, and deprecated features
are avoided.
Reviewer's Note:The following two success criteria seem to overlap with checkpoint 5.4. There is an open question about whether they should be deleted since Checkpoint 5.4 covers programmatic interfaces.
- for Application Programming Interfaces (API's), programming standards
for the language are followed.
- accessibility features and API's are used when available.
- for markup, the markup has passed validity tests of the language
(whether it be conforming to a schema, DTD, or other tests described in
the specification), structural elements and attributes are used as
defined in the specification, accessibility features are used, and
deprecated features are avoided.
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
Reviewer's Note: Are protocols relevant
to this checkpoint? If so, why, and should we require that they be used
according to specification? Obviously there are interoperability advantages
in doing so, but is this pertinent to accessibility?
- a list of technologies and features, support for which is required in order
for the content to be operable, has been determined and is
documented in metadata and / or a policy statement associated with
the content.
- Note: When determining your
list of technological requirements, consider that assistive hardware and software is often
slow to adapt to technological advances, and the availability of
assistive technology varies across natural languages. Verify that
assistive technology compatible with the technologies you choose is
available in the natural language(s) of your content.
- the content is still usable when features not on the
required list (for
example, scripting and stylesheets) are turned off or not supported.
- Technologies and features on the required list are
available in at least two independently-developed implementations.
- of at least two such implementations, it is true that the
technologies and features on the required list have been
supported by at least one prior version of the software.
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
- the technology or combination of technologies chosen:
- support device independence
- include accessibility features
- have publicly documented interfaces for interoperability
- make use of operating system accessibility features (either
directly or via the user agent) supported by assistive technologies
in the natural language(s) of the content
- are implemented in user agents and/or proxies in the natural
language(s) of the content
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
- any applications with custom user interfaces conform to at least Level
A of the User Agent Accessibility
Guidelines 1.0. If the application cannot be made accessible, an
alternative, accessible solution is provided.
- the interface has been tested using a variety of assistive technologies
and preferably real people with disabilities who use assistive
technologies to determine that assistive technologies can access all
information on the page or hidden within the page.
Reviewer's Note: It would be possible to comply with the
checkpoint without carrying out tests (either with users or with
assistive technologies). Conversely, it is possible to conduct tests, but
still fail to meet the checkpoint (with respect to assistive technologies
that were not tested, for example). Should this success criterion be
deleted?
- device-independent access to functionality is provided
- accessibility conventions of the markup or programming language (API's
or specific markup) are used
- (presently no additional criteria for this level.)
- (presently no additional criteria for this level.)
Reviewers Note: There are a number of open issues and questions related to this checkpoint. Some examples include:
- How can we provide guidelines related to this checkpoint for interactive content?
- How should WCAG 2.0refer to UAAG 1.0?
- How do other applications (ex. Java, PDF and Flash) fit into UAAG?
The WCAG WG has not tackled the definitions of the terms that we are using
and we sometimes use terms inconsistently. We need to coordinate our terms and
definitions with the WAI Glossary. We are working on proposals for a variety
of definitions. We have been looking at the UAAG 1.0 glossary and other
glossaries within the W3C. For now, a simple list of the terms that are defined in this
document are included below. Definitions for each term will be included at a
later date.
- text equivalent
- Non-text content
- time-dependent presentation
- Media equivalents
- captions
- audio descriptions
- Content
- Presentation
- Structure
- Natural languages
- keyboard interface
- Real-time events
- competitive activity
- structure
- site navigation mechanism
- Presentation
- Mechanisms that cause extreme changes in context
- Controlled languages
- Non-text content
- complex
- unfamiliar
- technology
- feature
Participants in the
WCAG Working Group
Since the release of WCAG 1.0 in May 1999, the WCAG Working Group has
received feedback on priorities of checkpoints, the usability of the set of
documents, and requests for clarifications on the meaning of specific
checkpoints and what is needed to satisfy them. Thus, it is intended that
WCAG 2.0, when it eventually becomes a W3C Recommendation:
- will be more efficiently organized,
- may adjust the priority of some checkpoints,
- may modify, remove, or add requirements due to changes in Web
technologies since the publication of WCAG 1.0,
- will incorporate the Errata from WCAG 1.0,
- will reflect the experience gained in implementing WCAG 1.0.
For a checkpoint by checkpoint comparison, refer to the Checkpoint Mapping Between WCAG
1.0 and the WCAG 2.0 Working Draft.
We hope that WCAG 2.0 will have several improvements over WCAG 1.0. While
the primary goal of WCAG 2.0 is the same as WCAG 1.0 (to promote
accessibility of Web content) additional goals for WCAG 2.0 include
improvements that will:
- Ensure that requirements may be applied across technologies
- Ensure that the conformance requirements are clear
- Ensure that the deliverables are easy to use
- Write to a more diverse audience
- Clearly identify who benefits from accessible content
- Ensure that the revision is "backward compatible" with WCAG 1.0
For more information about the intended improvements in WCAG 2.0 Working
Draft, please refer to Requirements
for WCAG 2.0.
Reviewer's Note: Links within the
document will be turned into references and the links to those documents will
be listed here as references. They are inline for the time being.