Action54AltAttributeSecondDraft

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Action 54: Second Draft

Statement of Purpose

The following second draft text is based on the February 6, 2008 PFWG finding that the HTMLWG:

"...re-work the <img> element section to bring it into line as techniques for implementing WCAG 2.0.We say 2.0 because of the strong likelihood that WCAG 2.0 will precede HTML5 to Recommendation status...

WCAG WG is chartered to set Accessibility guidelines and HTML WG is not; so HTML5 should be careful to create features that support WCAG and describe their use in ways that conform to WCAG."

The aim of this draft is therefore to comply with WCAG 2.0, Guideline 1.1. Text Alternatives:

"Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language..."

Further Advice

Additional advice has been sought, is needed, and is pending from PFWG for this action item regarding the following:

Second Draft Text for the HTML 5 Specification

Authoring Requirements

The src attribute must be present, and must contain a URI (or IRI). The alt attribute must present. Text alternatives are required as stated in WCAG 2.0, Guideline 1.1. Text Alternatives.

Text Alternatives

Note: The remainder of the authoring section of 3.14.2 is informative.

Text alternatives are a primary way for making information accessible, because they can be rendered through any sensory modality (for example, visual, auditory or tactile) to match the needs of the user. Providing text alternatives allows the information to be rendered in a variety of ways by a variety of user agents. For example, a person who cannot see a picture can have the text alternative read aloud using synthesized speech.

The value requirements for the alt attribute is dependent on the function of an image in the context of the document. To determine appropriate Text alternatives it is important to think about why an image is being included in a document. What is its purpose? Thinking like this will help you to understand what is important about the image for the page's intended audience. Every image has a reason for being on a page because it either provides useful information, performs a function, or enhances aesthetics. Therefore, knowing what the image is for, makes writing appropriate Text alternatives easier.

General alt Text Best Practices

  • Provide the same informational content as the image.
  • Where an image performs a specific function, such as a graphical link, provide information about its functionality.
  • Be succinct as possible while still conveying equivalent values. Short text that describes its purpose or gives an overview will often suffice.
  • Write suitable alt text according to context. The same image in a different situation may need very different alt text.
  • Avoid redundant alt text. An example of this would be repeating the same text in your document, as well as in the alt attribute, and is unnecessary.

Use Cases

General alt Text Example

A candid photograph of a dog digging in the sand on the beach.

<img src="dog.jpg" alt="A dog digging in the sand on the beach">
Authoring Techniques

For specific authoring techniques follow Techniques for WCAG 2.0.

Note: Usage examples and code samples from the Action 54 first draft are being refined and and most have already been submitted as Techniques for WCAG 2.0. If they are accepted, this document will link to them there. A format specification is not a tutorial. Including detailed guidance in ALT attribute techniques could be seen as usurping the role of WCAG 2.0 and its techniques documents. As PF has said, "WCAG WG is chartered to set Accessibility guidelines and HTML WG is not".

Use cases include but are not limited to:

  • Purely Decorative Images
    • Spacers
    • Bullets
    • Box corners
  • Complex Data Images
    • Charts
    • Graphs
    • Diagrams
    • Histograms
  • Other Complex Images
  • Pictures
    • Photographs
    • Paintings
    • Drawings
    • Artwork
  • Images of Text
    • Words
    • Phrases
    • Wordmark
    • ASCII Art
    • Mathematics
    • Equations
    • Formulæ
  • CAPTCHA Images
    • Obscured images of textual characters
    • Obscured image of words
  • Images of Symbols
    • Logos
    • Icons
    • Emblems
  • Functional Images
    • Navigation Links
    • Buttons

User Agent Requirements

Advice has been sought, is needed, and is pending from PFWG regarding the separate issue of what an authoring or publishing tool should insert, in a case where no alt has been provided by the author, but the image is known to be "critical content".

ATAG 1.0 Techniques

ATAG 2.0 Techniques

UAAG 1.0 Techniques

Editors

This document is authored and offered to the HTML WG by working group members:

  • Steven Faulkner
  • Joshue O Connor
  • Laura Carlson

Peer reviewed by:

  • Gez Lemon
  • Gregory J. Rosmaita

May 28, 2008.


Related References: