This technique relates to the following sections of the guidelines:
If the non-text content conveys information, then the text alternative must convey the same information. Ask, "What information does the non-text content convey?" and provide that information in text.
Determining what information the non-text content conveys may also require you to:
consider the context in which the non-text element occurs;
consider the non-text content both from
the content provider’s point of view and
from the user’s point of view.
What does the content provider want people to learn from the non-text content? What does the user need to learn from the text alternative? Is it important for users to draw their own conclusions based on the content as well as understanding the specific point the content-provider wanted to make?
Providing the information in text may require more than one step. For example, a complex image such as a chart, map, diagram, or photograph of an important person, place, event, or object may need two text alternatives:
to identify the non-text item and
to describe it or provide the information it conveys.
In the examples below, a single piece of non-text content is used in different contexts that require different text alternatives.
A photograph of an historic event. A photograph of two world leaders shaking hands accompanies a news story about an international summit meeting. The text alternative says, “President X of Country X shakes hands with Prime Minister Y of country Y.”
The same image used in a different context with additional text alternative. The image of the president shaking hands with the prime minister appears on a Web site discussing intricate diplomatic relationships. The first text alternative reads, “President X of country X shakes hands with Prime Minister Y of country Y on January 2, 2009.” An additional text alternative describes the room where the leaders are standing, the expressions on the leaders' faces, and identifies the other people in the room.
The additional description might be included on the same page as the photograph or in a separate file associated with the image through a link or other standard programmatic mechanism.
An audio recording. The Web page described in the previous example includes a link to an audio recording of the leaders' press conference. The page also links to a text transcript of the press conference. The transcript includes a verbatim record of everything the speakers say. It identifies who is speaking as well as noting other significant sounds that are part of the recording, such as applause, laughter, questions from the audience, and so on.
Editorial Note: Further discussion and examples are needed for real-time silent video such as webcams.
No related CSS Techniques
Excerpts from the NBA Tape Recording Manual, Third Edition. Information on describing complex images to people who are blind.