This page contains material related to a presentation at the Web Accessibility Best Practices Evaluation Training in Sankt Augustin, Germany on 25 October, 2005, as part of the WAI-TIES Project (WAI - Training, Implementation, Education, Support). It is not intended to stand-alone; rather, it is primarily provided as reference material for participants in the training.
Scope of Training and Materials: This one-day training focused on select topics that were particularly suited to the circumstances of this specific training session. It did not to cover all aspects of evaluating Web accessibility, and did not cover all Web Content Accessibility Guidelines (WCAG) 1.0 checkpoints.
No Endorsement or Recommendation of Evaluation Tools: W3C/WAI does not endorse Web accessibility evaluation tools and does not recommend one tool over another. Some tools were listed, demonstrated, and used in activities in this training. Mention of a specific tool does not imply endorsement nor recommendation. WAI does provide a comprehensive list of Evaluation, Repair, and Transformation Tools for Web Content Accessibility.
Evaluating Text Equivalents
Jon Dodd, Bunnyfoot
Last updated: 1 November 2005
Text = Flexibility
- The web is a flexible and empowering medium
- much of this flexibility is brought about because of text.
- Text can be transformed
- Text can be matched to the needs of people e.g.
- Text can substitute for information provided by other means = Text equivalent
- A text equivalent can be supplied for the following
- The result of scripts and applets
Text equivalents are vital for accessibility
- Probably the single most important violation of web accessibility is:
- Missing text equivalents for graphics (alt text)
- Probably the second most important violation of web accessibility is:
- Inappropriate text equivalents for graphics
- Equivalence is:
- NOT a literal description
- A functional description
- Describes purpose of the graphic/non text item
- Gets the intended meaning across
Types of text equivalent
- Presentation only graphics
- Complex graphics
- longdesc (html link to another page)
- Audio descriptions – definition and demonstration
- Captions, closed captions - definition
Problems for different people
- People who are blind using screen readers
- No access to image – no access to information/link/etc.
- Cannot see action in a video
- People with visual impairments
- Often text supplied as images – cannot scale – equivalent can
- People with hearing impairments
- No access to auditory alerts
- No access to auditory tracks of video
- No access to other auditory information
- Slow connections
- Different devices
- 1.1 - priority 1
- Provide a text equivalent for every non-text element (e.g., via "alt", "longdesc", or in element content). This includes: images, graphical representations of text (including symbols), image map regions, animations (e.g., animated GIFs), applets and programmatic objects, ascii art, frames, scripts, images used as list bullets, spacers, graphical buttons, sounds (played with or without user interaction), stand-alone audio files, audio tracks of video, and video.
- 1.2 - priority 1
- Provide redundant text links for each active region of a server-side image map.
- 1.3 - priority 1
- Until user agents can automatically read aloud the text equivalent of a visual track, provide an auditory description of the important information of the visual track of a multimedia presentation.
- 1.4 - priority 1
- For any time-based multimedia presentation (e.g., a movie or animation), synchronize equivalent alternatives (e.g., captions or auditory descriptions of the visual track) with the presentation.
- 6.2 - priority 1
- Ensure that equivalents for dynamic content are updated when the dynamic content changes.
- 6.3 - priority 1
- Ensure that pages are usable when scripts, applets, or other programmatic objects are turned off or not supported. If this is not possible, provide equivalent information on an alternative accessible page.
Evaluation methods – automated checks
Detect graphics + presence/absence of alt
- Site sweep, e.g.
- Page filter, e.g.
Evaluation methods – manual checks
- Use your mouse (IE) for a quick check
- Beware does not always work
- Beware of background and presentation only images
- Switch off images to assess equivalence
- View in page filter
- List links to test meaning out of context
- AIS toolbar
Evaluation methods – not just graphics
- Turning on captions and audio descriptions
- Scripts, objects, applets etc.
- Identifying <noscript>
- Identifying element contents