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Re: Writing good ALT descriptions


From: Iza Bartosiewicz
Date: Jul 23, 2009 7:30PM

Hi John,

These are the instructions for writing image descriptions I give to people:

1. Look at the image in its context
2. Determine its type/function it performs on the page (decorative, logo, link, illustration, text replacement...)
3. Write appropriate text replacement for that image, i.e.:

a) All decorative images should be in CSS; where this is not possible, provide blank alt text attribute
- it should be alt="" unless you are using a content management system that doesn't accept blank alt text, in which case you may need to add a space alt=" "

b) Provide an equivalent text alternative for all content and linked images. It must:
- be equivalent to the original content
- fulfill the same purpose as the original content
- describe the function not the image itself
- be concise

c) Complex images (maps, charts, graphs, illustrations) must have appropriate text alternative as well as long description.

Then I provide some examples.

Regarding the D link example from the list of links below, I no longer recommend using D links to provide long description. Not only D links have been deprecated in favour of 'longdesc' in WCAG 1.0, but the link text is not meaningful, so it doesn't meet the 13.1 checkpoint requirement (Clearly identify the target of each link).

A better approach is to make the link text meaningful, but WCAG 2.0 G73 suggests some other ways of fulfilling this requirement (http://www.w3.org/TR/WCAG-TECHS/G73.html) that may be preferred in some cases.

Hope this helps



Izabella Bartosiewicz
Web Coordinator
RMIT University Library

p 03 9925 3103
h www.rmit.edu.au/library

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>>> On 23/07/09 at 5:55, "Mills, Teresa" < <EMAIL REMOVED> > wrote:
> I point people to the following resources:
> (a) A text equivalent for every non-text element shall be provided (e.g., via
> "alt", "longdesc", or in element content).
> http://www.access-board.gov/sec508/guide/1194.22.htm#(a)
> http://www.jimthatcher.com/webcourse2.htm
> Related Information
> Creating Accessible Graphics (WEBAIM)
> http://www.webaim.org/techniques/images/
> Appropriate Use of Alternative Text
> http://www.webaim.org/techniques/alttext/
> Describing Illustrations, Diagrams, Maps, Tables, Charts, and Graphs
> http://www.w3.org/2000/08/nba-manual/Overview.html
> Guidelines on alt texts in img elements
> http://www.cs.tut.fi/~jkorpela/html/alt.html
> Example of D link
> http://www.consideration.org/technology/accessexamples/dlinksample.html